Mycology Virology Short And Long Essay Question And Answers

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

Read And Learn More: Microbiology Question and Answers

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