Virology

Clinical Microbiology Important Notes

1. Sexually transmitted diseases

• Syphilis
• Lymphogranuloma
• Herpes genitalis
• Gonorrhea
• AIDS

Clinical Microbiology Short Question And Answers

Question 1. Sore throat
Answer:

It is an acute tonsilitis and/ or pharyngitis

Sore throat Features:

• Redness and edema of the mucosa
• Exudation of tonsils
• Pseudomembrane formation
• Edema of uvula
• Enlargement of cervical lymph nodes

Sore throat Causative Organism:

Question 2. Name the micro-organisms causing meningitis.
Answer:

Micro-organisms causing meningitis are:

Question 3. Define Bacteraemia and Septicaemia
Answer:

Bacteraemia:

• It is defined as the presence of bacteria in blood without any multiplication

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Septicaemia:

• It is a condition in which bacteria circulate and actively multiply in the bloodstream

Question 4. Name micro-organisms causing infective endocarditis.
Answer:

Question 5. Name Sexually transmitted diseases
Answer:

Question 6. Stool examination
Answer:

Stool examination Uses:

• Stool examination is used to find out ova and cysts

Stool Examination Method:

• A drop of normal saline is placed at one end of a glass slide and a drop of iodine at the other end
• A minute of feces is added in both the drops and mixed
• A coverslip is gently placed over each
• Examine both under a microscope
• Any suspicious object if found is studied under high power microscope

Oral Microbiology Important Notes

1. Dental plaque consists of

• Bacteria
• Epithelial cells
• Macrophage
• Leucocytes

2. Factors producing dental caries

• Host – structure of tooth and nature of saliva
• Diet – carbohydrate rich diet
• Time – repeated ingestion of carbohydrate at short interval
• Microbial flora – Mainly Streptococcus mutans

Oral Microbiology Long Essays

Question 1. Discuss normal oral flora. What is the pathogenesis of dental plaque formation?
Answer:

Normal Oral Flora:

• The normal resident oral flora occupies available colonization sites which makes it more difficult for other micro-organisms to become established.
• At birth, the oral cavity is usually sterile
• But within a few hours first streptococci gets established followed by other species.
• Later the oral cavity becomes a mixture of bacteria, fungi, protozoan, and viruses.
• With the eruption of teeth, these organisms get colonized.
• Normal oral flora contains the following micro-organisms

Dental Plaque Formation:

• Initially, oral bacteria, pellicle, and dietary sucrose are required
• Pellicle contains salivary glycoprotein while bacteria produce adhesives like glucan from dietary sucrose
• The first pellicle through its glycoprotein gets adsorbed to the enamel surface and forms a membranous film

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• Next the glucan produced by the bacteria helps in binding the bacteria to the pellicle
• As this process continues more and more oral bacteria are adsorbed on the tooth surface
• As a result of it, layer called dental plaque is formed
• This later gets calcified to form calculus

Oral Microbiology Short Essays

Question 1. Dental plaque
Answer:

Dental plaque is a soft non mineralised deposit of bacteria present on the tooth surface and other hard surfaces of the oral cavity

Dental plaque Classification:

Dental plaque  Composition:

• Dental plaque consists of
  • Bacteria
  • Epithelial cells
  • Macrophages
  • Leucocytes

Dental plaque  Effects:

• Calculus formation
• Dental caries
• Periodontal diseases

Question 2. Dental caries
Answer:

• Dental caries is an infectious, microbiologic disease of the teeth that results in localized dissolution and destruction of the calcified tissues of the teeth.
• It leads to the weakening of tooth structure, cavity formation, and, eventual loss of tooth

Dental caries Etiology:

• Four factors interact to produce caries
• They are as follows:

Prevention of Dental Caries:

Dental caries can be prevented by

• Maintenance of good oral hygiene
  • By use of antimicrobials
  • Proper brushing
  • Flossing
  • By scaling at least once in 6 months
• Control of dietary carbohydrate intake
• Incorporating fluoride in drinking water
  • This increases resistance to dental caries.

Question 3. Periodontal infection
Answer:

• Periodontal infections include diseases of the gingiva, periodontal ligament, cementum, and alveolar bone
• Initially, the organisms affect the gingiva causing gingivitis
• Later it progresses to deeper tissues leading to progressive tooth loss

Periodontal infection Etiology:

• Periodontal microflora, intrinsic factors, and extrinsic factors cause periodontal diseases

Periodontal Diseases:

 

Oral Microbiology Short Question And Answers

Question 1. Microbiology or bacteria causing dental caries
Answer:

Bacteria that cause dental caries are

Question 2. Normal flora of the respiratory tract
Answer:

Question 3. Name micro-organisms causing a periapical abscess
Answer:

Micro-organisms causing periapical abscesses are:

Question 4. Oral antiseptics
Answer:

• Oral antiseptics re used to keep the commensal bacterial flora of the oral cavity clean
• Some of them act as a deodorant

Oral antiseptics Example:

• Thymol
• Menthol
• Eugenol
• Benzoic acid
• Boric acid
• Calcium
• Magnesium peroxide.

Helminths Long Question And Answers

Question 1. Describe the life cycle of ankylostoma duodenal. Write a note on pathogenicity and laboratory diagnosis of Ankylostomiasis
Answer:

The common name of ancylostoma duodenal is the old-world hookworm

Ankylostoma duodunale Life Cycle:

• Man is the only definitive host
• It involves following the steps

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Ankylostomiasis Pathogenicity:

• Migrating larvae may cause three types of lesions as follows

• The worm causes hookworm disease in man

Ankylostomiasis’s Clinical features are:

• Microcytic, hypochromic anemia
• Epigastric pain
• Dyspepsia
• Vomiting
• Diarrhea

Ankylostomiasis Laboratory Diagnosis:

1. Direct methods:

2. Indirect methods:

Question 2. Enumerate the common tapeworms. Describe the morphology, life cycle, and laboratory diagnosis of taeniasolium
Answer:

Tapeworms:

• Taenia saginata
• Taeniasolium
• Echinococcus granulosus

Taenia Solium Morphology:

 

Taenia Solium Life Cycle:

• The worm passes its life cycle in two hosts: the definitive host, man, and an intermediate host, pig
• The adult worm lives in the small intestine of man
• Eggs are passed out with the feces
• The animal swallows these eggs and gets infected
• Oncosphere hatches out
• It penetrates the gut wall
• Carried in the systemic circulation
• The naked Oncospheres are transformed into cysticercus cellulose in the muscle
• By intake of uncooked or partially cooked pork, enters into the alimentary canal of man
• The scolex of cysticercus evaginates and attaches to the gut wall
• It develops into an adult worm

Taenia Solium Laboratory Diagnosis

1. Stool examination

• It detects eggs of T. solium

2. Diagnosis of cysticercosis

• It is done by
  • Biopsy examination of subcutaneous nodules
  • X-ray of skull and soft tissues
  • CT scan of the brain
  • Eosinophilia

Question 3. Describe the morphology, life cycle, and pathogenesis of the Wuchereria branchfti. Discuss the diagnosis of filariasis.
Answer:

Wuchereria Branchfti Morphology:

1. Adult worms

• They are transparent, long hair-like structures
• Color-Creamy white
• Shape- Filiform with tapering ends

• Both remain coiled together
• Life span- 5-10 years

2. Embryos

• Color- colorless
• It is transparent
• Heads and tails- Heads are blunt while tails are pointed
• Size- 290 micrometer * 6-7 micrometer
• Covered by hyaline sheath
• Nuclei appear as granules

Wuchereria Branchfti Life Cycle:

• Wuchereria bancrofti passes its life cycle in man and mosquito
• Adult worms are present in the lymphatics system of man
• Male fertilises female
• Embryos or microfilariae are discharges
• These reach bloodstream
• Microfilariae are taken up by mosquitoes during a blood meal
• It develops in mosquito
• Through the bite of mosquito, the infective larvae are deposited on the skin
• This penetrates the skin and reaches the lymphatic channels
• Gets settled in lymph nodes
• Develops into an adult worm
• Again fertilization occurs and the cycle is repeated

Wuchereria Branchfti Pathogenesis:

• W. bancrofti causes filariasis

Wuchereria Branchfti Types:

Diagnosis Of Filariasis:

1. Direct methods

• Samples collected are
  • Blood
  • Chylous urine
  • Exudate of lymph varix
  • Hydrocele fluid
• Blood film should be made in night between 10 pm to 2 am as the number of microfilariae is more at night

2. Indirect methods

• It includes
• Blood examination- Detects Eosinophilia
• Serological tests like ELISA, indirect fluorescent antibody, and indirect haemagglutination assay.

Helminths Short Question And Answers

Question 1. Hydatid cyst:
Answer:

• The cyst wall secreted by the embryo
• It consists of the following.

1. Ectocyst
2. Endocyst

1. Ectocyst:

• It is a hyaline membrane which form thick, tough outer circular layer and is elastic in nature.
  • When incised it curls on itself
• As a result, it exposes the inner layer

2. Endocyst:

• It is inner (or) germinal layer
• It forms an ectocyst on outer side
• It gives rise to brood capsules and scolices on inner side.

Hydatid fluid:

• It is secreted by endocyst.

Hydatid cyst Characteristics:

• It is clear, colourless (or) pale yellow fluid.
• It is a slightly acidic nature
• It is highly toxic, when absorbed it gives rise to anaphylactic symptoms.
• Due to its antigenic nature it is used for Casoni’s test.
• It has a low specific gravity
• Composition- It contains
  • Sodium chloride
  • Sodium sulfate
  • Sodium phosphate
  • Sodium and calcium salts of succinic acid

Hydatid sand:

• It is a granular deposit which consists of brood capsules, free scolices, and loose hooklets.
• It gets settled at the bottom of the hydatid cyst

Question 2. cassoni’s test
Answer:

It is an immediate hypersensitivity skin test introduced by Casoni in 1911.

Cassoni’s test Method:

• Sterile hydatid fluid is used as an antigen.
• Hydatid fluid is obtained from hydatid cyst from humans or animals
• It is made of sterile
• Now 0.2 ml of it is injected intradermally in one arm
• While 0.2 ml of normal saline is injected intradermally in the other arm

Cassoni’s test Result:

• It produces a large wheal measuring 5 cm in diameter or more within 30 minutes in all positive cases.
• Also shows multiple pseudopodia.

Question 3. Microfilaria
Answer:

• Microfilariae are the larvae of nematodes.
• The female nematodes are viviparous giving birth to larvae called microfilariae.
• It needs two hosts to complete its life cycle man and a blood-sucking insect

Microfilaria Features:

Question 5. Cysticercus Ceilulosae
Answer:

• Cysticercus cellulose is the larval stage of taenia solium
• It develops in the muscles of the pig which is an intermediate host
• A mature cyst is an opalescent ellipsoidal body and the long axis of the cyst is parallel to the muscle fiber.
• A dense milky white spot is present at the side where the scolex with its hooks and suckers remains invaginated.
• The cyst develops further when ingested by man which is the definitive host
• It may develop in any organ but are usually present in the subcutaneous tissues and muscles.

Various features of cysticercosis.

• They cause palpable nodule in sub-cutaneous tissues and muscles
• In the brain leads to epileptic attacks.
• Neurocysticercosis involving the nervous system is the most serious form

Question 6. Diagram of Fertilised egg of ascaris lumbricoides
Answer:

Question 7. Life cycle of Ascaris lumbricoides
Answer:

• Ascaris lumbricoides passes its life cycle in only one host i.e. Man
• Adult worms reside in the jejunum of man
• The passing of Fertilised eggs containing the unsegmented ovale in the feces
• These develop in soil
• Rhabditiform larva develops from the unsegmented ovum
• This undergoes first molting
• Intake of food, drink or raw vegetables contaminated with eggs containing Rhabditiform larvae causes infection in man
• Liberation of Rhabditiform larvae occurs in the upper part of the small intestine
• They burrow through the mucous membrane of the small intestine
• It is carried to the liver and then enter pulmonary circulation
• They reach lungs and enlarge
• They break through the capillary wall and reach alveoli
• The larvae reach the bronchi, then the trachea and are swallowed after reaching the pharynx
• Pass down to esophagus, stomach and then gets localized in the upper part of the small intestine
• Here another molting occurs and the larvae grow into an adult worm
• Thus the cycle repeats

Question 8. Larva migrans
Answer:

It is a condition caused by ingestion of embryonated eggs of some nematodes parasitizing animals

Larva migrans Pathogenesis:

• Larvae are hatched in the small intestine
• These reach extraintestinal sites
• Gets settled in the liver, lungs, and other organs
• This leads to the formation of granulomatous lesions

Larva migrans Clinical Features:

• Leucocytosis
• Eosinophilia

Larva migrans Diagnosis:

• Serological tests detect antibodies in serum

Larva migrans Prevention:

• Deworming animals prevent this disease

Question 9. Name four tapeworms.
Answer:

• Taeniasolium
• Taeniasaginata
• Echinococcusgranulosus
• Diphyllobothrium latum
• Hymenolepsis nana

Protozoans Important Notes

1. Entamoeba histolytica

• Occurs in three forms
  • Trophozoites
  • Pre cystic stage
  • Cyst
    • It passes its life cycle only in man
    • Diseases caused by it
      • Intestinal amoebiasis
      • Extra intestinal amoebiasis
        • Other Entamoeba are
          • Entamoeba coli
          • Entamoeba gingivalis

2. Species of Plasmodium

• Pvivax
• P falciparum
• P malariae
• P ovale

3. Stages of the life cycle of Plasmodium

• Pre erythrocytic schizogony
• Erythrocytic schizogony
• Gametogony
• Exo erythrocytic schizogony

4. Malarial pigment

• Yellowish brown – P. vivax
• Dark brown – P.falciparum, P.malariae
• Dark yellowish brown- P.ovale

5. Malaria

• Clinical features
  • Febrile paroxysm
  • Anaemia
  • Splenomegaly
• Complications
  • Pernicious malaria
  • Black water fever

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6. Cestodes

• Taenia saginata
• Taenia solium

7. Nematodes

• Ascaris lumbricoides or round worm
• Hookworm
  • Ankylostoma duodenale
  • Wuchereria bancrofti

Protozoans Long Essays

Question 1. Describe the morphology, pathogenesis, and life cycle of Entamoeba histolytica. Write about laboratory diagnosis of intestinal amoebiasis.
Answer:

Entamoeba histolytica causes intestinal amoebiasis and hepatic amoebiasis

Entamoeba histolytica Morphology:

The parasite exists in 3 forms

Entamoeba histolytica Life Cycle:

• E. histolytica passes its life cycle in only one host, the man.
• The mature quadranucleate cysts are infective forms.
• These cysts enter in to men through ingestion of water and food containing it
• These reach the caecum or lower part of the ileum called excystation
• Each mature cyst liberates tetranuclear amoeba
• Forms eight meta cystic Trophozoites by binary fission
• It gets lodged in the submucous tissue of the large intestine
• E.histolytica secretes a proteolytic enzyme
• Causes destruction and necrosis of tissues
• Results in the formation of flask-shaped ulcers
• Next, these Trophozoites are
  • Excreted along with blood and mucous in feces
  • Results in amoebic dys­entery
  • Enter into deeper layers
  • Enter into the portal vein
  • Reaches liver
  • Forms amoebic hepatitis and amoebic liver abscess
• Effect of the parasite on the host decreases
• This increases host tolerance and healing starts
• Encystation occurs which is the transformation of Trophozoites into cysts and cysts.

Entamoeba histolytica Pathogenesis:

E. Histolytica can cause two types of pathological lesions as follows

1. Primary (or) Intestinal Amoebiasis:

• This condition is called as amoebic dysentery.
• This ulcer maybe generalized (or) may be localized to the ileocaecal (or) sigmoidorectal region.
• Occasionally ulcers may involve deeper tissues and may cause perforation (or) peritonitis.
• Erosion of blood vessels may lead to hemorrhage.
• The superficial lesions generally heal without scar¬ring.
• Deep ulcers form scars leading to strictures, partial obstruction, and thickening of the gut wall

2. Extra-intestinal amoebiasis [or) secondary (or) metastatic lesions.

• Amoebic liver abscess:

Laboratory Diagnosis of Intestinal Amoebiasis:

1. Stool examination:

• The stool is collected directly into a wide-mouthed con¬tainer and examined without delay.
  • Macroscopic Examination
    • The stool is an offensive odor
    • Dark brown and semifluid
    • Acid in reaction
    • Mixed with blood and mucous
  • Microscopic Examination
    • The cellular exudates is scanty, and consist of nuclear masses of a few pus cells, macrophages, and epithelial cells
    • RBCs are seen in clumps
    • Charcot- Leyden crystals are also seen

2. Blood Examination

• In early cases, it is always negative
• The antibody can be detected in later stages of invasive intestinal amoebiasis
• The test used is ELISA haemagglutination assay (HIA).

3. DNA Probes:

• DNA probes have been used to detect E. histolytica in stool specimens.

Question 2. Describe the life cycle of malarial parasites in man. Give a brief description of pathological lesions produced in man.
Answer:

Malaria is a disease caused by four plasmodium species which are as follows:

• P. vivax
• P. Falciparum
• P. Malaria
• P. Ovale.

Malarial Life Cycle:

The malarial parasites pass their life cycle in two. hosts.

1. Man intermediate host [a sexual development]
2. Female anopheles mosquito – definitive host [sexual development].

Human cycle or schizogony or a sexual cycle:

• The sporozoite is the infective form of a malarial parasite.
• Man gets infected by the bite of the infected female Anopheles mosquito
• This mosquito contains sporozoites in the salivary gland which enter directly into the blood circulation of man
• By this human cycle starts which comprises of following stages.

1. Pre-erythrocytic schizogony

• It is a developmental phase of sporozoites inside the liver cells
• The shape of sporozoites- Round
• Size-Varies
• They undergo nuclear division to develop schizont
• Each schizont contains 20,000-50,000 merozoites
• Duration of this stage
  • P. vivax           – 8 days
  • P. falciparum  – 6 days .
  • P. malariae     – 13-16 days
  • P. ovale          –  9 days
• After this period, the liver cells rupture
• As a result, merozoites are released into the bloodstream

2. Erythrocytic schizogony:

• Release of merozoites into the blood
• Penetration of it into RBCs
• Rupture of RBCs which leaves behind a residue of hemoglobin pigment called hemozoin
• Release of merozoites
• These attack new RBCs
• Thus the cycle continues

3. Gametogony:

• Some merozoites develop sexual forms known as microgametocytes and macro gametocytes

4. Exo-erythrocytic schizogony:

• Some sporozoites enter liver cells but don’t multi-ply
• Enter in the resting phase and are known as Hypno- zoite
• These hypnozoites get reactivated
• Forms schizonts
• Releases merozoites called phanerozoic
• Attack RBCs
• Causes relapse of malaria

Malaria Clinical Features:

• Intermittent fever which is named as malaria is caused by plasmodium
• It consists of

1. Febrile paroxysm

• It comprises of three stages

2. Anaemia

• Microcytic or normocytic hypochromic anemia develops

3. Spenomegaly.

• The spleen becomes enlarged and palpable
• Black water fever, and pernicious malaria are the most commonly seen complications in falciparum malaria.

Protozoans Short Essays

Question 1. Laboratory diagnosis of extraintestinal amoe¬biasis
Answer:

Diagnostic methods for extraintestinal amoebiasis are as follows

Question 2. Leishmania donovani
Answer:

It causes visceral leishmaniasis or kala-azar

Leishmania donovani Morphology:

It occurs in two forms:

Leishmania donovani Life Cycle:

• The parasite has two stages in its life cycle
  • Amastigote form
  • Promastigote form
• Initially, multiplication of amastigote form occurs in the reticuloendothelial cells in the host
• Enlargement of host cells occurs
• These cells rupture to release parasites into circulation
• Blood-sucking insect obtains it by sucking
• Development of Promastigote form from Amastigote form

Leishmania donovani Clinical Features:

• Pyrexia
• Splenomegaly
• Hepatomegaly
• Lymphadenopathy
• Anaemia

Question 3. The life cycle of plasmodium in mosquito
Answer:

• The sexual development of plasmodium occurs in mosquito
• It starts in the human host by the formation of Gametocytes
• The cycle includes the following steps
• Bite of female anopheles from the patient
• Mature sexual forms develop in the mosquito
• In the midgut
• 1 microgametocytes- develops 4-8 microgametes
• 1 macrogametocyte- Develops 1 macrogamete
• Fertilization of macrogamete occurs
• Formation of zygote
• Lengthening and maturation of zygote to form ookinete
• Formation of oocyst from ookinete
• Maturation of oocyst
• Increase in size and number of sporozoites
• Rupture of oocyst to release sporozoites in the body of the mosquito
• Distribution of sporozoites into various organs and tissues especially in salivary glands

Question 4. Laboratory diagnosis of malaria
Answer:

The demonstration of the parasite in the blood is the most important method for the diagnosis of malaria.

1. Microscopic examination of blood film:

• Thick and thin smears of blood are prepared on the same slide (or) two different slides.
• Blood is collected prior to antimalarial therapy

2. Fluorescent microscopy:

• A blood smear is prepared on a slide and is stained with acridine orange
• The slide is observed under a fluorescent microscope.
• The nuclear DNA of the malarial parasite is stained green and cytoplasmic RNA is stained red.

3. Blood counts:

• Blood shows moderate leukopenia and monocytosis.

4. Serological tests:

• Serological tests used are
  • ELISA
  • Indirect haemagglutination assay
  • Indirect immunofluorescence test.

5. DNA probes:

• These are sensitive and specific diagnostic methods for the diagnosis of malaria
• It can detect even a low parasitemia i.e., <10 parasites/dl

6. Polymerase chain reaction (PCR):

• It can also be used.

7. Rapid diagnostic tests:

• These are based on the detection of antigens using immune chromatographic methods.
• In these tests, a dipstick containing monoclonal antibodies is directed against the parasitic antigens.
• This test takes about 15 minutes.
• Several commercial kits are available.
• Kits available detect histidine-rich protein (HRP – II) of P. falciparum.
• The test is commercially available as the parasite ‘F’ test.

Question 5. Complications of plasmodium falciparum infection?
Answer:

Complications of P.Falciparum are:

1. Pernicious malaria
2. Black water fever.

1. Pernicious malaria:

• It is life-threatening condition

Pernicious malaria Cause:

• It is due to heavy parasitization.

Pernicious Malaria Clinical Features:

• It is grouped into the following:

2. Blackwater fever:

Occurs in persons who are previously infected and had inadequate doses of quinine

Black water fever Clinical Features:

• Intravascular hemolysis,
• Fever,
• Haemoglobinuria
• Vomiting and prostration with the passage of dark red (or) blackish urine hence called backwater fever.

Black water fever Mechanism:

• An autoimmune mechanism may be involved in hemolysis
• Parasitized erythrocytes during previous infection act as antigen
• Antibodies are formed against it
• Due to this antigen-antibody reaction, massive destruction of erythrocytes occurs
• There is excessive deposition of haemosiderin pigment in the liver, spleen, and kidneys.
• Sequel of black water fever include
  • Circulatory failure
  • Renal failure,
  • Liver failure,
  • Anaemia.

Protozoans Short Question And Answers

Question 1. Draw morphological forms of Entamoeba His¬tolytica
Answer:

Question 2. Amoebic dysentery
Answer:

• Amoebic dysentery is also known as intestinal amoebiasis
• It is a condition in which the infection is confined to the intestine and is characterized by the passage of blood and mucus in the stool

Amoebic dysentery Types:

1. Acute amoebic dysentery

• Multiple ulcers occur
• These ulcers are deep and extensive
• Its complications are
  • Pericaecal and pericolic abscess
  • Amoebic appendicitis
  • Perforation
  • Generalized peritonitis
  • Gangrene of guts
  • Fistula

2. Chronic amoebic dyssentery

• A single latent ulcer is present in the caecum while multiple small superficial ulcers are scattered throughout the large intestine
• Stricture formation occurs
• Amoeboma in the caecum and large intestine develops

Question 3. E.gingivalis / Morphology of E.gingivalis
Answer:

E.gingivalis Morphology:

• It is a small amoeba measuring 10 – 20 (m in diameter and is actively motile by multiple pseudopodia.
• It has the only trophozoite stage and there is no cystic phase.
• It contains
  • The cytoplasm which is divided into clear ectoplasm and granular endoplasm.
  • Cytoplasmic inclusions consisting of bacteria leucocytes but never RBCs
  • Nucleus is spherical
  • Central karyosome.
  • Nuclear membrane lined with closely packed chromatin granules.

E.gingivalis Pathogenesis:

• E.gingivalis is a parasite of human mouth.
• It occurs as a commensal in gingival tissue around the teeth particularly in the unhealthy tissues such as in pyorrhoea alveolaris.
• It is also found in the crypts and histologic sections of diseased tonsils.
• It is transmitted by close contact like kissing.
• Laboratory diagnosis depends on the demonstration of tro¬phozoites of E. Gingivalis in the material removed from the gingival margin of the gum (or) from the denture.

Question 4. Erythrocytic schizogony
Answer:

• It is the second stage of the human cycle of the malaria parasite
• During this phase, the parasite resides inside RBC and passes through stages of Trophozoites, schizonts, and merozoites.
• Following changes occur during this phase
• Release of merozoites into the blood

Question 6. Plasmodium falciparum
Answer:

Plasmodium falciparum is one of the malarial parasites

Stages of Human Cycle in P. Falciparum:

• P. falciparum is the most pathogenic among the plasmodium species infecting man
• No relapse occurs in P.falciparum infection
• It invades erythrocytes of all ages
• The incubation period of it is 10-14 days

Complications:

• Pernicious malaria
• Black water fever

Question. Black water fever
Answer:

Occurs in persons who are previously infected and had inadequate doses of quinine

Black water fever Clinical Features:

• Intravascular hemolysis,
• Fever,
• Haemoglobinuria
• Vomiting and prostration with the passage of dark red (or) blackish urine hence called backwater fever.

Question 9. Kala-azar
Answer:

Leishmania denovani produces the disease Salazar (or) visceral leishmaniasis.

Kala-azar Clinical Features:

• Pyrexia,
• Splenomegaly,
• Hepatomegaly,
• Lymphadenopathy and
• Anaemia.

Kala-azar Laboratory Diagnosis:

1. Direct evidence:

2. Indirect evidence:

3. Rapid immune chromatographic strip test:

• It detects antibodies against the K39 antigen of L. donovani
• It indicates active kala-azar

Question 10. Benign tertian malaria
Answer:

• Benign tertian malaria is caused by Plasmodium vivax
• Initially, there may be continuous or remittent fever
• In later stages, typical intermittent periodic fever develops
• Initially, two broods of parasites undergo schizogony on alternate days but then one brood drops out.

Question 11. Mention the parasites found in peripheral blood smear.
Answer:

Mycology Important Notes

1. Classification of fungi

• Phycomycetes or zygomycetes
• Ascomycetes
• Basidiomycetes
• Fungi imperfect

2. Types of spores.

• Sexual spores – oospore, ascospore, zygospore and basidospore
• Vegetative or asexual spore- blastospore, arthrospores, chlamydospores

3. Lab diagnosis used for fungal infection

• KOH mounts
• Wood’s lamp
• Sabouraud’s glucose agar and cornmeal agar culture media
• Microscopic examination

4. Types of hair infection

• Endothrix
• Ectothrix

5. Candidiasis

• Causative agent – Candida albicans
• Classification
• Acute
  • Pseudomembranous
  • Acute atrophic
• Chronic
  • Chronic hyperplastic
  • Chronic atrophic
• Complications
  • Intestinal Candidiasis
  • Bronchopulmonary Candidiasis
  • Septicemia
  • Endocarditis
  • Meningitis

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6. Aspergillosis

• It is the most opportunistic pathogen
• Caused by inhalation
• Diseases caused by it are
  • Aspergillus asthma
  • Bronchopulmonary aspergillosis
  • Colonizing aspergillosis
  • Invasive or disseminated aspergillosis
  • Superficial infections

Mycology Long Essays

Question 1. Give an account of infections caused by Can¬dida albicans. Describe the laboratory diagnosis of Candida.
Answer:

Infections Caused by Candida:

Lesions caused by Candida are as follows.

1. Oral thrush Features:

• The lesions appear soft, white, and slightly elevated plaques
• Sites:
  • Buccal mucosa
  • Tongue
  • Gingiva
  • Palate
  • The floor of the mouth
  • The entire oral cavity is involved in severe cases
• Person affected are
  • HIV patients
  • Cancer patients undergoing chemotherapy or radiotherapy
  • Neonates and infants
  • Debilitated and chronically ill patients

2. Chronic oral candidiasis

• Caused by denture-induced stomatitis or chronic hypertrophic candidiasis

3. Chronic mucocutaneous candidiasis

• Integral lesions are similar to other types
• Extraoral lesions involve skin, nails, and mucous

4. Angular stomatitis

• Effects lips
• Common in immunocompromised patients

5. Circumoral candidal dermatitis

• Involves lips and area around lips

Candida Laboratory diagnosis:

1. Direct microscopy:

• Gram-stained smears and KOH mounts from le¬sions of skin, nail (or) mucous membrane are used
• These show budding Gram-positive yeast cells.

2. Culture:

• Sabouraud’s dextrose agar media (SDA)
  • SDA is inoculated and incubated at 25 – 37° C for 24 hours.
  • Cream-coloured smooth pasty colonies appear.
  • On gram staining of it shows gram positive bud¬ding yeast cells.

3. Identification:

Candida albicans can be identified by

• Germ tube test:
  • When incubated in human serum at 37oC, C. al-beans form germ tubes within two hours. – This is called Reynolds braude phenomenon
• Chlamydospores.
  • Chlamydospores develop in cornmeal agar at; 20 degrees C.

4. Biochemical reactions:

• C. albicans can be identified by the assimilation and fermentation of sugar.

5. Serology: 

• C. Albicans can also be identified by the precipita¬tion test with a carbohydrate extract of group A an¬tigens.

Mycology Short Essays

Question 1. Mycetoma/Madhura foot.
Answer:

• Mycetoma is a chronic granulomatous infection of the subcutaneous tissue
• It usually affects the foot but rarely even other parts of the body
• Commonly seen in tropical countries.

Mycetoma Synonyms:

• Madhura foot as it was first described from Madurai South India.
• Madhuramycosis.

Mycetoma Etiology:

Causative agents are

• Eumycetoma
  • Madhuvella mycetomi
  • Acremonium falciforme.
  • Actinomycetoma.
• Actinomadura Madurai
  • Nocardia
  • Streptomyces.

Mycetoma Pathogenesis:

Mycetoma Treatment:

Question 2. Actinomycosis.
Answer:

It is a chronic granulomatous disease

Actinomycosis Causative Organism:

Actinomycosis Forms:

Actinomycosis Features:

It is characterized by

• Multiple abscesses
• Tissue destruction
• Fibrosis
• Formation of multiple sinuses
• Painless indurated swelling
  • It may cause gingivitis and periodontitis

Actinomycosis Diagnosis:

1. Microscopy

• Steps
  • Dilute the pus with saline in a test tube
  • Allow it to settle
  • Sulfur granules are obtained from it
  • These granules are crushed between slides
  • Smears are prepared
  • One of them is Gram stained and the other is acid-fast stained
  • Observe these smears
• Observations
  • Gram-stained smear shows Gram-positive filaments surrounded by peripheral radiating Gram-negative clubs
  • This results in a sun-ray appearance
  • Acid-fast smears show the central part of non-acid fast clubs surrounded by acid-fast clubs

2. Culture

Cultural media used are

• Thioglycollate broth
• Brain heart infusion agar
• Blood agar
  • They are incubated anaerobically and aerobically with 5% CO2 at 37 degrees C for 2 weeks
  • It results in spider colonies

Actinomycosis Treatment:

• It involves surgical removal of affected part
• The antibiotic used in such cases is penicillin

Question 3. Pathogenesis of Candida albicans.
Answer:

• Candidiasis is an opportunistic endogenous infection
• Predisposing factors are:
  • Diabetes
  • Immunodeficiency
  • Malignancy
  • Prolonged administration of antibiotics
  • Patients on immunosuppressive drugs and intra¬venous catheters
• Lesions caused by it:

Mycology Short Question And Answers

Question 1. Ray fungus
Answer:

• Actinomyces are known as ray fungus
• They are
  • Gram-positive
  • Non-motile
  • Non-sporing
  • Non arid fast organism
• They appear as granules in the pus.
• When these granules are crushed between two slides and Gram stained, they show a central filamentous mycelium surrounded by a peripheral zone of swollen radiating club-shaped structures
• This gives it a sun-ray appearance
• They cause actinomycosis

Question 2. Rhinosporidiasis.
Answer:

Rhinosporidiosis is a chronic granulomatous disease.

Rhinosporidiasis Causative Organism:

• Rhinosporidium seeberi.

Rhinosporidiasis Mode of Infection:

• Frequent contact with stagnantwater.

Rhinosporidiosis Features:

• Friable polyps
• Sites involved- nose, mouth, and eye
• Oral manifestations are Oropharyngeal lesions
• They appear as soft red polypoid growth and spread to the pharynx and larynx.
• These lesions contains mucoid discharge and are vascular.

Rhinosporidiosis Diagnosis:

• H and E stained tissue sections show a large number of endospores within the sporangia
• These are embedded in a stroma of connective tissue, and capillaries

Question 3. Cryptococcosis?
Answer:

It is caused by a Cryptococcus neoformans, a capsu- lated yeast

Cryptococcosis Morphology:

• A spherical budding cell having a prominent polysaccharide capsule.
• It is a true yeast and gram-positive.

Cryptococcosis Pathogenesis:

• Occurs through inhalation

Sites Involved:

• Skin
• Lymph nodes
• Bones
• Cutaneous lesions characterized by small ulcers to large granuloma

Laboratory diagnosis:

• Laboratory diagnosis is done by direct microscopy, culture, latex agglutination test, and animal inoculation test

Question 4. Aspergillosis?
Answer:

Aspergillosis Etiology:

• Aspergillosis is caused by inhalation of aspergillus co- nidia (or) mycelia fragments which are present on the decaying matter, soil (or) air.

Aspergillosis Forms:

3 clinical forms of aspergillosis are

Aspergillosis Laboratory Diagnosis:

• KOH smears show non-pigmented septate hyphae with characteristic dichotomous branching.

Culture:

• The clinical specimen is inoculated on SDA without cycloheximide and incubated at 25oC.
• Colonies appear within 2 days

Colonies:

• It shows a velvety to powder surface and are colored.

Question 5. Name three opportunistic fungi.
Answer:

• Some saprophytic fungi usually do not produce disease but may cause infection under special conditions such as immune-compromised individuals and terminal stages of chronic disease.
• These are called as opportunistic fungi.

Examples are:

Predisposing conditions:

• Widespread use of antibiotics, corticosteroids
• Immunosuppressive drugs
• Immunosuppressive diseases like AIDS.

Question 6. Mention two important media for culturing fungi.
Answer:

• Sabouraud’s dextrose agar (SDA)
• SDA medium with antibiotics
• Brain heart infusion (BHI) agar with blood and antibiotics.
  • Fungi are incubated at 37 degrees C and 25 degrees C for 3 weeks in SDA medium
  • Chloramphenicol is added in the culture medium to suppress the growth of contaminating bacteria while cyloheximide is incorporated to suppress the contaminating fungi.

Question 7. Fungus affecting hair
Answer:

• Dermatophytes are the group of fungi affecting hair.
• Favus is a chronic type of ringworm involving the hair follicles

Fungus affecting hair Features:

• Alopecia
• Scarring
• Sparse hyphal growth
• Formation of air spaces within the hair shaft

Fungus affecting hair Types:

Question 8. A quick method of diagnosing Cryptococcus neoformans.
Answer:

• The latex agglutination test is a quick method for diagnosing Cryptococcus neoformans
• In this test, polystyrene latex particles are employed to absorb the antigen
• Latex agglutination tile is used in it
• The antigen detected is Cryptococcal capsular polysaccharide antigen
• The specimen used is CSF, serum or urine.

Question 9. Mention two oral fungal infections
Answer:

• Oral fungal infections are:
  • Rhinosporidiosis
  • Sporotrichosis
  • Histoplasmosis
  • Blastomycosis
  • Candidiasis

Retrovirus HIV Important Notes

1. HIV

• Mode of transmission
  • Sexual intercourse
  • Blood and blood products
  • Tissue and organ donation
  • Injections and injuries
  • Mother to baby
• Clinical features
  • Low-grade fever
  • Malaise
  • Headache
  • Lymphadenopathy
  • Spontaneous resolution within weeks
  • Seroconversion illness at 3 to 6 weeks
• Diagnosis
  • Screening test – ELISA test
  • Confirmatory test – Western blot test, polymerase chain reaction

Retrovirus HIV Short Essays

Question 1. HIV virus
Answer:

HIV occurs in two main types,

1. HIV-1
2. HIV-2

HIV virus Morphology:

• HIV is a spherical-enveloped virus
• Size: 90-120 nm in diameter
• It contains
  • Two identical copies of single-stranded RNA genome
  • Reverse transcriptase enzyme
  • Nucleocapsid surrounding the core
  • Lipoprotein envelope
  • Projecting spikes on the surface
  • Anchoring transmembrane pedicles

Read And Learn More: Microbiology Question and Answers

HIV virus Modes of Transmission:

There are three modes of transmission

1. Sexual contact
2. Parenteral transmission
3. Perinatal transmission

HIV virus Clinical Features:

It is classified into various groups by the Center for Disease Control in Atlanta, USA

1. Group 1- Acute HIV infection
2. Group 2 – Asymptomatic infection
3. Group 3- Persistent generalized lymphadenopathy
4. Group 4- Symptomatic HIV infection

HIV virus Oral Manifestations:

• Greater risk for bacterial, viral, and fungal infections
• Dental caries
• Gingivitis
• Acute necrotizing ulcerative gingivitis
• Herpes Simplex infections
• Hairy leukoplakia
• Candidiasis

HIV virus Diagnosis:

• Immunological tests:
  • Total leucocyte count
  • Lymphocytes count
  • T cell subset assays
  • Platelet count
  • Raised IgG and IgA levels
  • Diminished CM1
  • Lymph node biopsy
• Specific Tests:
  • Antigen detection
  • Virus Isolation
  • Polymerase chain reaction
  • Antibody detection

HIV virus Screening Tests:

• ELISA test
• Karpastest
• Rapid tests
• Indirect immunofluorescence

HIV virus Confirmatory Tests:

• Western blot test

Retrovirus HIV Short Question And Answers

Question 1. Mention modes of transmission of infection of HIV
Answer:

Question 2. HIV infection
Answer:

• Human immunodeficiency virus ( HIV] is the etiological agent for AIDS
• HIV infects all cells
• It infects primarily the CD4+ lymphocytes
• The Center for Disease Control in Atlanta, USA, has classified the clinical course of HIV infection into various groups

Question 3. ELISA test
Answer:

• Most widely used screening test
• It is highly sensitive and specific.
• Direct solid phase antiglobulin ELISA is the method most commonly used for which commercial test kits are available.
• The antigen is coated on the microtiter wells (or) another suitable solid surface.
• The test serum is added and if antibodies are present it binds to the antigen.
• After washing away the unbound serum, antihuman immunoglobulin linked to the suitable enzyme is added followed by color forming substrate.
• If the test serum contains anti-HIV antibodies a visible (or) photometrical detectable color is formed which is read visually (or) by an ELISA reader.
• ELISA has a sensitivity of over 99.5%
• It is extremely good screening test
• Commercial ELISA test kits contain both HIV 1 and HIV 2 antigens.

Question 4. Mention opportunistic infections associated with HIV infection
Answer:

Question 5. Window period
Answer:

• After infection, for antibodies to appear it may take 2-8 weeks to months.
• IgM antibodies appear first usually in about 3-4 weeks after infection and disappear in 8-10 weeks
• IgG antibodies appear later about 5-6 weeks after infection and persist throughout
• During part of this period, the individual may be highly infectious
• This seronegative infective stage is known as the window period
• Infection can be detected during the window period by p24 assay

Question 6. Rapid tests for HIV infection
Answer:

• A number of rapid tests have been introduced for the purpose of testing single samples quickly
• They take less than 30 minutes
• They don’t require any expensive equipment
• These tests include:
  • Dot-blot assay
  • Particle agglutination
  • HIV spot
  • Comb tests
• Tests using finger-pricked blood, saliva, and urine have also been developed

Question 7. Western blot test
Answer:

• Most widely used confirmatory test for HIV.
• In this test, HIV proteins are separated according to their electrophoretic mobility and molecular weight by polyacrylamide gel electrophoresis.
• These separated proteins are bloated on the strips of nitrocellulose paper. These strips are reacted with test sera and then with enzyme-conjugated antihuman globulin.
• Antibodies to HIV protein present in test serum combine with all (or) any fragment of HIV.
• These strips are washed and treated with enzyme-conjugated antihuman gammaglobulin, then a suitable substrate is added that produces colour bands.
• The position of the band on the strip indicates the antigen with which the antibody has reacted.
• In the positive serum, bands will be seen with multiple proteins typically with p24, p31, gp41, gpl20 (or) gpl60.

Question 8. Draw labelled diagram of HIV.
Answer:

Bacteriophage Important Notes

1. Bacteriophage

• They are viruses that infect bacteria
• Helps in the transmission of genetic information between bacteria by transduction

Bacteriophage Short Essays

Question 1. Bacteriophage?
Answer:

The viruses that infect bacteria are known as bacterio-phages

Bacteriophage Morphology:

Bacteriophages are tadpole-shaped and are made up of

1. A hexagonal head

• The head consists of a tightly packed core of nucleic acid surrounded by a protein coat or capsid
• The size varies from 28 nm – 100 nm.

2. A cylindrical tail and

• The tail is composed of a hollow core, a contractile sheath surrounding the core

3. Baseplate.

• Terminal base plate which has attached to its prongs, tail fibers or both.
• Bacteriophages that infect E.Coli called T- even phages (T2, T4, T6) traditionally serve as the prototypes in describing the properties of bacteriophages.
• They possess double-stranded DNA.

Bacteriophage Significance:

Hepatitis Viruses Important Notes

1. Hepatitis virus

Hepatitis Viruses Long Essays

Question 1. Describe the morphology, spread, prevention, and lab diagnosis of hepatitis B virus
Answer:

Hepatitis-B Virus:

It belongs to the Hepadnaviridae family

Hepatitis-B Morphology:

• It is a complex structure
• Size: 42 nm
• It is a double-shelled particle

Hepatitis-B Structure:

1. Outer surface or envelope

• It contains hepatitis B surface antigen, HBsAg.
• It encloses the inner core

Read And Learn More: Microbiology Question and Answers

2. Core

• It is an Icosahedral nucleocapsid
• Size: 27 nm
• Contains hepatitis B core antigen, HBcAg

3. Genome

• It is present inside the core
• It is double-stranded DNA and DNA polymerase
• Sera of hepatitis B patients shows three types of particles microscopically.

Antigenic Structure:

Spread:

There are three modes of transmission

Prevention:

1. General preventive measures

• It includes:
  • Health education
  • Improvement of personal hygiene
  • Sterilization measures
  • Screening for HBsAg and HBeAg in blood donors
  • Avoiding the use of unsterile needles, syringes or other materials

2. Immunization

Hepatitis-B Laboratory Diagnosis:

• Dark urine and yellow coloration of sclera due to jaundice occurs
• Blood shows lymphocytosis
• Prolonged prothrombin time occurs

Question 2. Describe the pathogenicity and laboratory diagnosis of the hepatitis B virus.
Answer:

Pathogenicity of Hepatitis B Virus:

• Pathogenesis of hepatitis appears to be immune-mediated
• HBV causes serum hepatitis
• Infection spreads by
  • Blood transfusions
  • Serum inoculation
  • Sharing of syringes and needles
  • Sharing of razors
  • Tattooing
  • Acupuncture
  • Sexual intercourse
• It is more common in drug addicts, prostitutes and homosexuals
• Virus is highly infectious and even minute quantity of carrier sera can transmit the infection

Hepatitis B Virus Clinical Features:

• Incubation period- 2-6 months
• Onset – Slow, insidious, severe
• Fever is not prominent
• The course of acute HBV infection is divided into three phases:

• Extrahepatic complications include
  • Urticaria
  • Arthralgia
  • Polyarteritis nodosa
  • Glomerulonephritis
  • The appearance of circulating immune complexes obtaining viral surface antigen
• Some patients progress to chronic active hepatitis and cirrhosis

Hepatitis Viruses Short Essays

Question 1. Differentiate between hepatitis A and hepatitis B.
Answer:

Hepatitis Viruses Short Question And Answers

Question 1. Danes particles.
Answer:

• Under the electron microscope, sera from type B hepatitis patients show three types of particles
• The third type of particle is a double-walled spherical structure
• It is 42 nm in diameter
• It is the complete hepatitis B virus
• It was first described by Danes in 1970
• Hence it is known as the Danes particle

Question 2. Quantitative rapid test for hepatitis B antigen
Answer:

The Serological tests used for hepatitis B antigens are

• DNA hybridization
• Polymerase Chain Reaction
  • They detect HBV DNA
  • They are highly sensitive
  • They are quantitative tests

RNA Viruses Important Notes

1. Inclusion bodies

2. Infections caused by human papillomavirus

• Verruca Vulgaris
• Focal epithelial hyperplasia
• Condyloma acuminatum

Read And Learn More: Microbiology Question and Answers

3. Types of rabies vaccine

• Semple vaccine
• BPL (Beta propriolactone) vaccine
• Infant brain vaccine

RNA Viruses Short Essays

Question 1. Polio Vaccine
(or)
Immunoprophylaxis for Poliomyelitis
Answer:

The two types of polio vaccines are as follows

1. Salk’s Polio Vaccine:

• It was developed by Salk in 1953.
• It is formalin in-activated preparation of the three types of the polio virus grown in monkey kidney tissue cultures.
• Viral pools of adequate titre are filtered to remove the cell debris and clumps and inactivated with formalin at 37°C for 12-15 days.

Router of Administration:

The vaccine is given by deep subcutaneous (or) in- tra muscular injection.

Salk’s Polio Vaccine Doses:

Three doses are given 4-6 weeks apart followed by a booster dose should be given six months later.

• The first dose should be given after the age of six months so that antibody response is not impaired by the residual maternal antibodies.
• Immunity can be sustained by booster doses every 3-5 years thereafter.

Salk’s Polio Vaccine Mechanism:

• This vaccine produces long-lasting immunity to all three poliovirus types.
• Induces serum antibodies

2. Sabin’s Vaccine:

• It was developed by Sabin in 1962
• It contains live attenuated strains of poliovirus types, 1, 2, and 3 grown either in monkey kidney cells (or) human diploid cell cultures.

Sabin’s Vaccine Route of Administration:

• It is administered orally so known as the oral polio vaccine (OPV).

Sabin’s Vaccine Mechanisms:

• It stimulates both local secretory IgA antibodies in the intestine as well as humoral antibodies (IgM and IgG).
• When the virus is excreted in the faeces, it may spread to close contacts
• Thus it protects the individual and the community

Sabin’s Vaccine Doses:

• Three doses are given
• All doses are generally given along with DPT.
• In addition to it, the following doses are given

Question 2. Mumps:
Answer:

• Mumps is an acute viral infectious disease character¬ised by unilateral (or) bilateral nonsuppurative enlargement of the salivary glands usually the parotid gland.
• Submandibular and sublingual glands are occasionally involved.
• Usually, children are affected. May also occur in adults.
• Also known as epidemic parotitis

Mumps Causative organism:

• Organisms involved in paramyxovirus.

Mumps Route of infection:

• Infection is acquired by inhalation (or) direct contact or through the conjunctiva.
• The incubation period is 12 – 18 days.

Mumps Clinical Features:

• Unilateral (or) bilateral swelling of parotid glands.
• Fever, malaise
• Local pain and tender
• The involvement of extra parotid sites can cause more serious problems as follows.
  • CNS involvement may lead to
  • Meningitis,
  • Meningoencephalitis
  • Orchitis

Mumps Complications:

• Orchitis
• Oophoritis
• Arthritis
• Nephritis
• Pancreatitis
• Thyroiditis and myocarditis.

Mumps Laboratory Diagnosis:

• Isolation of viruses from CSF, saline (or) urine.
• Serological tests with paired serum samples are tested for the rise in the titer of antibodies by complement fixation test ELISA, haemagglutination tests.
• Serum amylase levels are elevated in both parotitis and acute pancreatitis.
• Mumps Treatment: Treatment is conservative maintaining hydration.
• Prevention is by means of the MMR vaccine.

RNA Viruses Short Question And Answers

Question 1. Name 3 RNA viruses and diseases caused by them.
Answer:

Question 2. Mention two important live viral vaccines.
Answer:

Live viral vaccines are

Question 3. Koplik’s spots?
Answer:

• Koplik’s spots are named after Henry Koplik who first described it in 1896
• Koplik’s spots are seen in measles (or) rubella
• Immune reaction to the virus in endothelial cells of dermal capillaries plays a role in the development of spots.

Koplik’s Spots Appearance:

• These are small irregularly shaped flecks
• They appear as bluish-white flecks surrounded by a bright red margin.
• The spots disappear after the onset of the rash.
• Orally they are most commonly observed on the buccal mucosa opposite to the lower molars
• With the decline of acute symptoms, widespread mac papular rash over the neck
• It then spreads to the rest of the body
• The rash fades in about a week
• The patient recovers by 10-14 days

Question 4. Inclusion bodies?
Answer:

• Inclusion bodies are distinctive structures frequently formed in the nucleus (or) cytoplasm in cells infected with certain viruses.
• These are 3 types based on location
  • Intranuclear
  • Intra cytoplasmic
  • Both.
• They are also known as cellular inclusions.
• Examples are:
  • Intra-cytoplasmic and intra-nuclear
    • Negri bodies – rabies
  • Intra-cytoplasmic
    • Henderson – Peterson bodies – molluscum conta- gypsum
  • Intra – nuclear
    • Cow dry type A – Herpes, yellow fever
    • Cow dry type B – Adenovirus, poliomyelitis.

Question 5. Name four vaccines
Answer:

Question 6. Mumps vaccine?
Answer:

• An effective live attenuated vaccine [Jeryl Lynn strain of mumps virus] grown in chick embryo fibroblast cul¬ture is against mumps.
• The vaccine is given as single subcutaneous infections either alone (or) in combination with the MMR vaccine.
• The vaccine is not protective to individuals already exposed to the virus and whose are in the incubation stage of the disease.
• The MMR vaccine provides effective protection for a period of 10 years.

Mumps vaccine Contra-indications:

• Pregnancy
• Immunodeficiency
• Hypersensitivity neomycin or egg protein.

Question 7. Arboviruses
Answer:

• Arboviruses are RNA viruses that are transmitted by blood-sucking arthropods from one vertebrate host to another
• Mosquitoes, ticks and sandflies are the principal vectors
  • They are named according to the
    • Disease caused by them- example. Yellow fever
    • Place of isolation- for example Kyasanur forest disease
    • The local name of the disease- for example Chickengunya
  • They are classified according to their physical and chemical features into five families
    • Togaviridae
    • Flaviviridae
    • Bunyaviridae
    • Rheoviridae
    • Rhabdoviridae

Arboviruses Disease Caused by Them:

• Encephalitis
• Haemorrhagic fever

Arboviruses Diagnosis:

The diagnosis is made by virus isolation and serologi¬cal tests

Question 8. Rabies vaccine
(or)
Immunization of rabies
Answer:

• Rabies vaccines are two types

1. Neural
2. Non-neural

1. Neural Vaccines:

• Semple vaccine:
  • The most widely used vaccine
  • Developed by Semple at Central Research Insti¬tute, Kasauli.
  • It is a 5% suspension of infected sheep brain and inactivated by 5% phenol at 37°C leaving no re¬sidual live virus.
• Beta Propiolactone (BPL) Vacine:
  • Modified semple vaccine
  • Instead of phenol, BPL is used as inactivating agent.
• Infant brain vaccine:
  • Used widely in South America
  • Reduce neurological complications.
• Vaccination Schedules:
  • Nowadays not used.
  • In the past, they were given subcutaneously on the anterior abdominal wall.
  • 7 – 14 injections depend on the degree of risk.

2. Non-Neural Vaccines:

• Duck Egg Vaccine:
  • BPL is used as an inactivating agent
  • It has poor immunogenicity so not used now.
• Tissue culture vaccines: Following cell culture vaccines are available in India.
  • Human diploid cell strain vaccine [HDCS]
    • The HDCS vaccine is prepared by growing rabies virus on human diploid cells and is in¬activated with BPL.
    • This vaccine is highly antigenic and free of side effects
  • Purified chick embryo cell vaccine [PCEC]
    • PCEC is now widely used.
    • It is cheaper
    • It contains BPL inactivated flurry LEP strain
  • Purified Vero cell vaccine [PVC]
    • This vaccine is under study

Question 9. Kyasanur forest disease
Answer:

• It is a tick-borne haemorrhagic fever that occurs in Agar and Sorab, Shikarpur talukas of Shimoga district in Karnataka state
• It is locally known as monkey fever as it infects mon¬keys also
• But infection in monkeys is fatal

Kyasanur forest disease Causative Organism:

• It is caused by the Russian Spring-Summer Encephalitis ( RSSE) Complex
• Forest birds, and small mammals are the reservoir hosts
• Principal vector is Haemaphysalis spinigera

Kyasanur forest disease Clinical Features:

• Sudden onset with fever, headache, conjunctivitis, myalgia and severe prostration
• Some may develop haemorrhages in the skin, mucosa and viscera

Question 10. Japanese Encephalitis
Answer:

Japanese Encephalitis Causative Organism:

• Japanese encephalitis virus causes Japanese B encepha¬litis.
• The virus in one of the mosquito-borne groups of a valve viruses.
• Culex tritaeniorhyncus – Principal vector
• Herons – Reservoir hosts.
• Pigs – Amplifier hosts.

Japanese Encephalitis Clinical Features:

• The disease typically has an abrupt onset with fever, headache and vomiting.
• The fever is high and continuous.
• The majority of infections are asymptomatic.
• After 1-6 days signs of encephalitis set in with nuchal rigidity, convulsions, altered sensorium and coma.
• The majority of infections are asymptomatic.
• After 1-6 days signs of encephalitis set in with nuchal rigidity, convulsions, altered sensorium and coma.

Japanese Encephalitis Laboratory Diagnosis:

• There is neutrophil leucocytosis in the peripheral blood
• Pleocytosis with normal (or) raised sugar and slightly raised protein in the CSF.

Japanese Encephalitis Immunisation:

• A formalin-inactivated mouse brain vaccine produced by using Nakayama strain has been successfully used for human immunization in Japan and even in India also.
• 2 doses at 2 weeks interval followed by a booster 6 – 12 months later constitutes a full course.
• Subsequent booster doses are recommended every 3 – 4 years as the immunity produced by the vaccine is short-lived.

Question 11. Human papillomaviruses [HPV]
Answer:

• Human papilloma viruses belong to papovaviruses.
• These are small, non-enveloped. Icosahedral oncogenic DNA viruses.
• It can cause cutaneous warts, genital warts, recurrent respiratory papillomatosis, and oral papillomatosis.
• These infections are transmitted by indirect (or) direct contact including sexual contact.
• An association between HPV infection (HPV types 16 and 18) and cancer of the uterine cervix.

Question 12. Viruses causing diarrhoea.
Answer:

• Diarrhoea is defined as an increase in the frequency, fluidity or volume of bowel movements relative to the usual habits of an individual.
• Viruses causing diarrhoea include.
  • Rotavirus
  • Norwalk virus
  • Adenovirus
  • Astrovirus
  • Coronavirus
  • Calicivirus

Question 13. Oncogenic herpes viruses
Answer:

Oncogenic herpes viruses cause various malignant diseases.

Question 14. Name oncogenic viruses
Answer:

The various Oncogenic viruses are as follows:

Question 15. Oncogenic RNA viruses
Answer:

• Oncogenic RNA viruses belong to Retroviruses, which are enveloped, spherical viruses
• They developed by budding through the host cell membrane
• It contains enzyme RNA-dependent DNA polymerase or reverse transcriptase within the virion
• It is classified into three subfamilies as follows
  • Oncovirinae
  • Spumavirinae
  • Lentivirinae
• These viruses induce tumours by
  • Introducing into the cellular genome or by
  • Inducing or altering the expression of a pre-existing cellular gene.

Question 16. MMR.
Answer:

• It is a live viral vaccine
• It is used for Mumps, Measles and Rubella
• It provides effective protection for a period of 10 years
• It is recommended for all infants at the age of 15 months followed by a booster at the age of 4-6 years.

Side effects of MMR vaccine:

• Sore arm
• Fever
• Mild rash
• Temporary pain and stiffness in joints

DNA Viruses Important Notes

1. Herpesvirus Subfamilies:

• Alpha herpes virus
  • Herpes simplex 1
  • Herpes simplex 2
  • Varicella zoster
• Beta herpes virus
  • Cytomegalovirus
• Gamma herpes virus
  • Epstein Burr virus
  • Human herpes type 8

2. Infections caused by Epstein Barr virus

• Infectious mononucleosis
• Burkitt’s lymphoma
• Nasopharyngeal carcinoma

DNA Viruses Short Essays

Question 1. Herpes virus
Answer:

The Herpes virus belongs to the Herpes viridian family

Subfamilies:

Herpes virus Morphology:

• Size: 100-200 nm in diameter
• It contains:
  • Icosahedral caused containing 162 capsomers
  • Double-stranded DNA genome
    • It is surrounded by a lipid envelope containing peplomers
    • The tegument is present between capsid and envelope

Read And Learn More: Microbiology Question and Answers

Herpes virus Laboratory Diagnosis:

• It includes
  • Collection of specimen
  • Smear preparation
  • Staining of specimen
  • Observation
    • It shows Tzanck cells, Multinucleated giant cells, Cowdry type A intranuclear inclusion bodies
  • Tissue culture
  • Polymerase Chain Reaction

Question 2. Herpes simplex virus?
Answer:

• It is a DNA virus
• It belongs to the herpesviridae family.
• Man is the only natural host.
• Herpes simplex virus are two types as follows.
  • Herpes simplex type 1 – is usually associated with oral and ocular lesions.
  • Herpes simplex type 2 – is usually associated with genital infections.
    • Lesions caused by herpes simplex depend on the site of infection, age and immune status of the individual are as follows:
  • Cutaneous infections: These include:
    • Fever
    • Blisters on the cheeks, chins around the mouth, (or) on the forehand
    • Napkin rash on the buttocks of children, – Herpetic widow in medical professionals.
  • Eczema herpeticum:
    • The generalized herpetic eruption is seen in children suffering from eczema.
  • Mucosal lesions:
    • Acute gingivostomatitis
    • Recurrent herpes labialis.
  • Ophthalmic lesions:
    • Keratoconjunctivitis
    • Follicular conjunctivitis.
  • Visceral lesions:
  • Nervous system:
    • HSV meningitis,
    • Sacral autonomic dysfunction.
  • Genital lesions:
    • Infection of the cervix, vagina, or vulva (females)
  • Congenital lesions:
    • Subclinical or localised infection of skin mouth or eyes.
    • Besides primary infections, herpes viruses may present as latent infection, reactivation and re- crude scene.

Herpes simplex virus Laboratory Diagnosis:

Question 3. Cytomegalovirus?
Answer:

• Cytomegalovirus is included in herpeviridae family.
• It is a Human Herpes Virus 5 (HHV-5)
• The virus is shed in urine, saliva, semen, cervical secretions, tears and breast milk.

Cytomegalovirus Pathogenesis:

• Cytomegalo virus infections are almost always inapperent leading to prolonged latency with occasional re-activation.
  • Congenital infections:
    • Cytomegalovirus can be transmitted transplacentally from a mother with latent infection to the foetus.
    • Infections are asymptomatic at birth (or) it may lead to cytomegalic inclusion disease which is often fatal.
    • Cytomegal inclusion disease is characterised by:
      • Hepatosplenomegaly.
      • Jaundice
      • Thrombocytopenic purpura
      • Haemolytic anaemia
      • Microcephaly.
  • Post Natal Infections:
    • Are usually asymptomatic
    • Clinical disease in adults resembles infectious mononucleosis.
    • It can cause dissemeinated infection in immune-compromised individuals like AIDS patients.

Cytomegalovirus Laboratory diagnosis:

• Specimens can be obtained from saliva, urine, breast milk, semen etc.
• The smear shows enlarged cytomegalic cells with large intra-nuclear owl’s eye appearance
• Inclusions can be demonstrated in the centrifuged de-posits from urine (or) saliva.
• The virus can be grown in human fibroblast culture detected by ELISA test.

Cytomegalovirus Treatment:

Ganciclovir is the drug of choice.

Question 4. Adenovirus
Answer:

• Adenovirus belongs to the Adenoviridae family
• They replicate in the nucleus of infected cell

Adenovirus Classification:

• Adenovirus are grouped into
  • Aviadenovirus- Possess avian adenovirus
  • Mastadenovirus- Possess mammalian adenovirus

Adenovirus Morphology:

• Size- 70-75 nm in diameter
• It is non-enveloped
• Contains
  • Icosahedral capsid
  • Double-stranded DNA

Adenovirus Pathogenesis:

• Adenovirus causes infections of the respiratory tract, eye, GIT and urinary tract
• The mode of the spread of infections include
  • Conjunctiva
  • Nasal mucosa
  • Faeco-oral spread
• The incubation period is 5-7 days

Adenovirus Laboratory Diagnosis:

DNA Viruses Short Question And Answers

Question 1. Smallpox
Answer:

• The causative organism of smallpox is the variola virus
• It was exclusively human infection with no animal reservoir
• It used to occur in two distinct varieties

1. Florid

• It is a highly fatal disease
• Seen in Asia

2. Alastrim

• It is a mild non-fatal disease
• Seen in Latin America
• Variola major caused smallpox
• Now it has been eradicated
• Due to which the vaccination of it is now stopped
• It was last detected in Somalia, in October 1977.
• On May 8, 1980, WHO announced the global eradication of small pox

Question 2. Name the disease caused by DNA viruses.
Answer:

Question 3. Herpes Zoster
Answer:

• It is caused by the Varicella Zoster virus
• It is a disease of old age
• It occurs in persons who had chickenpox several years earlier

Herpes Zoster Pathogenesis:

• The virus remains latent in the sensory ganglia
• Due to a decrease in immunity, this virus gets reactivated
• It is triggered by some precipitating stimulus
• It results in the inflammation of the nerve

Herpes Zoster Clinical Features:

• Skin lesions
• Neuritic pain- It is severe and persists for weeks or months
• Unilateral Vesicles
• Oral manifestations include:
  • Unilateral involvement of skin areas supplied by ophthalmic, mandibular or Maxillary nerves
  • Painful vesicles are present on the buccal mucosa, tongue, pharynx and larynx
  • Vesicles rupture leaving areas of erosion

Question 4. Antiviral agents
Answer:

Antiviral agents are agents that selectively attack one of the stages of viral replication without harming the host cells.

Examples:

Question 5. Epstein- Barr virus or EB virus
Answer:

• Epstein-Barr virus is named after its discoverers Epstein, Barr and Achong in 1964.
• Infection with the EB virus leads to
  • Latency
  • Periodic reactivation
  • Lifelong persistence
  • Infects B lymphocytes
• Diseases caused by it are
  • Infectious mononucleosis
  • EBV associated malignancies

• • • Burkin’s lymphoma
    • Lymphoma in immuno-deficient persons
    • Nasopharyngeal carcinoma

General Properties Of Viruses Important Notes

1. Features of virus

• Lacks enzymes required for protein and nucleic acid synthesis
• Do not possess cellular organization
• Contains only one type of nucleic acid
• Multiply by a complex process

2. Structure Consists of

• Genome
• Capsid
• Envelope

3. Cultivation of virus

• Animal inoculation
• Embryonated egg inoculation
• Tissue culture

4. Classification of virus

• Enveloped and non-enveloped virus
• Based on their affinity to a different system
  • Thermotropic
  • Neurotropic
  • Pneumotropic
  • Viscerotropic

General Properties Of Viruses Long Essays

Question 1. Explain the methods of isolation of viruses.
Answer:

Methods employed for the cultivation of viruses are

• Animal inoculation.
• Embryonated egg inoculation.
• Tissue culture.
  • Organ culture
  • Explant culture
  • Cell culture

Read And Learn More: Microbiology Question and Answers

• Animal inoculation Uses:
  • Primary isolation of certain viruses
  • To study viral oncogenesis
  • To study the pathogenesis of certain viruses.
  • Animals used are
    • Mice – for arboviruses and coxsackie virus
    • Guinea pigs.
    • Rabbits
  • Routes of inoculation used
    • Intracerebral
    • Sub-cutaneous
    • Intraperitoneal
    • Intranasal
  • Steps
    • Inoculation of animals
    • Observation of animals for signs of disease
    • Animals are killed
    • Their tissues are tested for the presence of virus
• Embryonated egg inoculation:
  • Embryonated hen’s eggs are inoculated by different routes

• Tissue Cultures:
  • Cell Culture:
    • Routinely employed for diagnostic virology.
    • Tissues are disassociated into the component cells by the action of proteolytic enzymes such as trypsin.
    • Cell cultures are classified into three types based on their origin, and chromosomal characteristics.

General Properties Of Viruses Short Essays

Question 1. Mention the characters of viruses.
Answer:

General Characters of Viruses:

• Viruses are the smallest obligate intracellular infective agents.
• Only one type of nucleic acid either DNA (or) RNA act as their genomes.
• They have no metabolic activity outside the living cells.
• They do not possess a cellular organization.
• They lack the enzymes necessary for protein and nucleic acid synthesis.
• They do not grow in inanimate media.
• They are resistant to antibiotics.
• They multiplied by a complex process but not by binary fusion.
• They are ultramicroscopic particles.

General Properties Of Viruses Short Question And Answers

Question 1. Classification of viruses
Answer:

• Viruses are classified into two major groups based on the nucleic acid they possess
• They are:

Dna Viruses:

• Poxviridae family
• Herpes viridian family
• Adeno viridian family
• Pap ova viridian family
• Parvo viridian family
• Hepadna viridae family

Rna Viruses:

• Picorna viridae family
• Orthomyxo viridian family
• Paramyxo viridian family
• Toga viridian family
• Flavi viridian family
• Rhabdo viridian family
• Retro viridian family
• Corona viridae family
• Filoviridae family