Systematic Bacteriology

Bacillus Short Question And Answers

Question 1. Morphology of bacillus anthracis.
Answer:

• Bacillus anthracis is
• Gram-positive
• Non-acid fast.
• Non-motile.
• Spore forming.
• Capsulated – polypeptide in nature.
  • Size – Large, 3-10 Elm x 1 – 1.6 Elm.
  • Shape – Rectangular.
  • Spores – Refractile, oval, and central in position.
  • Spores are of same width as the bacillary body.
  • Thus, they do not cause bulging.

Bacillus anthracis Arrangement:

1. In infected tissues:

• Bacilli are found singly, in pairs or in short chains.
• The entire chain is surrounded by a capsule.

2. In culture.

• In bacilli are arranged end-to-end in long chains.
• The ends of the bacilli are truncated or often con-cave and somewhat swollen.
• This gives it a bombastic appearance.

Question 2. Cultivation of Bacillus Anthracis.
Answer:

Bacillus anthracis is an aerobe and facultative anaerobe.

• Grows in a temperature range of 12-45°C.

Question 3. Malignant pustule.
Answer:

It is a feature of cutaneous anthrax

• Site of entry
• Abraded skin.

Affected sites involved are:

• Face
• Neck
• Hands
• Back

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The persons involved are:

• Farmers
• Persons handling dead bodies.

Malignant pustule Features:

• The lesion starts as a papule which becomes a vesicle containing fluid called a pustule.
• The acute inflammatory reactions lead to congestion and edema of the area with central necrotic lesions.
• This lesion is called a malignant pustule.

Question 4. Types of diseases caused by B. Anthracis.
Answer:

There are three clinical types of diseases caused by B. Anthracis based on the route of infection.

Streptococcus Long Essays

Question 1. Write in detail about the morphology, pathogenesis, laboratory diagnosis, and treatment of streptococcus pyogenes.
Answer:

Streptococcus pyogenes:

• Morphology:
  • Streptococcus pyogenes are:
    • Gram-positive are:
    • Non-sporing.
    • Non-motile.
    • Capsulated.
    • Aerobe and facultative anaerobe organism.
  • Size – 0.5 – 1 micrometer in diameter.
  • Shape – spherical or oval.
  • Arrangement – arranged in a chain.
  • It occurs due to successive cell divisions occurring in one plane only.

Streptococcus Pathogenesis:

• Streptococcus Pyogenos adheres to the pharyngeal epithelium by means of lipoteichoic acid covering the surface epithelial cells.
• The infection may spread to the surrounding tissues leading to suppurative complications.
  • Otitis media.
  • Mastoiditis.
  • Quinsy.
  • Ludwig’s angina.
  • Suppurative adenitis.
  • Rarely meningitis.
• Scarlet fever occurs which leads to sore throat and a generalized erythematous rash.

Streptococcus Laboratory diagnosis:

Streptococcus Treatment:

• Penicillin G – is the drug of choice for all streptococcal infections.
• In the case of a patient allergic to penicillin, erythromycin or cephalexin is used.

Question 2. Classify streptococci. Describe the toxins and lesions produced by β-hemolytic streptococci.
Answer:

Streptococcus Classification:

Streptococci are classified as follows:

1. Based on 0₂ requirement.

• Aerobic and facultative anaerobes.
• Obligate anaerobes
• Example: peptostreptococcus.

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2. Based on hemolytic property.

Toxins produced by streptococci:

Lesions:

1. Pyogenic infections:

• Respiratory infection.
  • The throat is the primary site of invasion causing a sore throat
    • Tonsilitis – localized in tonsils.
    • Pharyngitis – involves the pharynx.
    • Pyogenic complications like otitis media – are caused by the spread of streptococcal infections to surrounding tissues.
    • Streptococcal pneumonia.
• Skin and soft tissue infections.
  • Cause suppurative infections of the skin. Examples are wounds, burns, cellulitis, and lymphangitis.
  • Typical skin infections include.
    • Erysipelas – It is a diffuse infection involving superficial lymphatics.
    • Impetigo – leads to glomerulonephritis in children.
      • Genital infection includes puerperal sepsis.
• Other infections.
  • Includes sepsis, pyemia, septicemia, and abscess of internal organs.

2. Non-suppurative complication.

It includes:

• Acute rheumatic fever.
  • It is preceded by a sore throat
  • It is characterized by fever, pancarditis, migratory polyarthritis, and sometimes chorea and subcutaneous nodules.
  • Repeated attacks are common.
  • It shows a marked immune response.
• Acute glomerulonephritis.
  • It is preceded by a skin infection.
  • It is self-limiting and resolves without any permanent damage.
  • Pathogenesis may be due to antigenic cross-reaction between glomerular antigens and some components of nephritogenic streptococci.
  • It shows’s moderate immune response.

Question 3. Enumerate the etiology of sore throat. Describe the pathogenesis and complications of streptococcus pharyngitis.
Answer:

Sore throat:

It is an acute tonsillitis/ pharyngitis

Sore throat Etiology

• Bacteria
  • Streptococcus pyogenes
  • Streptococcus groups C and G
  • Corynebacterium diphtheria
  • Haemophilus influenza
  • Bordetella pertussis
  • Treponema vincentii
• Fungus
  • Candida albicans
• Viruses
  • Epstein Burr virus
  • Adenovirus
  • Coxsackie virus A

Streptococcus Pathogenesis:

• Streptococcus is the leading cause of pharyngitis
• Cell surface accounts for its virulence
• It is concerned with colonization and evasion of phagocytosis and host immune responses
• The surface contains capsular polysaccharides, cell wall peptidoglycan, lipoteichoic acid, and surface proteins and cell bound streptokinase
• Cytoplasmic membranes contain antigens that suppresses host immune system

Streptococcus pharyngitis Complications

• A sore throat may lead to rheumatic fever
• It is characterized by inflammation of joints and/or heart following streptococcal pharyngitis

Streptococcus Short Essays

Question 1. Enzymes of streptococci.
Answer:

Enzymes:

Question 2. Cultural characteristics of streptococcus.
Answer:

Streptococcus is an aerobe and facultative anaerobe.

• It best grows at 37oC and pH – 7.2 – 7.4
• Growth occurs only in media enriched with blood, serum or sugars.

• Virulent strains on isolation produce finely granular colonies.
• Avirulent strains form glossy colonies.
• Strains with well-marked capsules form mucoid colonies.

Question 3. Discuss streptococci under the following heading
-Dental caries
Answer:

Streptococci Dental Caries:

• Dental caries is caused by Str. Mutans.
• It produces enzyme called glucosyltransferase
• This enzyme breaks down dietary sucrose production.

1. Acid

• It leads to the demineralization of the tooth enamel and the initiation of carious lesions.

2. Dextran.

• It binds together with food debris, mucus, epithelial cells, and bacteria to form plaque.
• This plaque leads to dental caries.
• Once the caries process is initiated, it progressed by lactobacilli.
• Other streptococci involved are.
  • Str. Milleri.
  • Str. Sangus.
  • Str. Salivaris.
  • Str. Mitior.

Question 4. Viridans group of streptococci.
Answer:

• Viridans group of streptococci produces alpha hemolysis on blood agar.
• They are commensals of the mouth and upper respiratory tract.

Streptococci included in viridian group:

• Str. Mitis group.
• Str. Anginosus group.
• Str. Bovis group.

Each group contains many species.

Diseases caused by them:

They are usually non-pathogenic but can cause disease.

1. Dental caries.

2. Subacute bacterial endocarditis.

• Predisposing factors are valvular heart diseases, congenital heart diseases, and cardiac surgery.
• Following tooth extraction, transient bacteremia occurs.
• This gets implanted on damaged or prosthetic valves.
• They form vegetation.

Prevention:

• Prophylactic antibiotics should be given before extraction.
• Antibiotic sensitivity must be determined.
• Caries preventive measures should be carried.

Question 5. Antistreptolysin O test.
Answer:

Antistreptolysin O test is a toxin neutralization test used to detect the presence of antistreptolysin O in the patient’s sera.

Antistreptolysin O:

• It is an antitoxin secreted by the body against the exotoxin streptolysin O of streptococci.
• It blocks the hemolysis caused by streptolysin O.

Antistreptolysin O Value:

• Higher than 160 or 200 titer – indicated prior strepto-coccal infection.
• Higher level – indicates acute rheumatic fever.

Antistreptolysin O Uses:

• Aid in the diagnosis of rheumatic fever and acute glomerulonephritis.
• Used for retrospective diagnosis of streptococcal pyoderma.

Streptococcus Short Questions And Answers

Question 1. Streptococcal infections.
Answer:

1. Pyogenic streptococcal infections.

• Respiratory infections.
  • Sore throat
  • Tonsillitis
  • Pharyngitis.
• Skin and soft tissue infections
  • Wounds
  • Burns.
  • Lymphangitis
  • Cellulitis
  • Erysipelas.
  • Impetigo.
• Genital infections – puerperal sepsis.
• Other infections.
  • Septicaemia.
  • Pyaemia
  • Abscess of internal organs.

2. Nonsuppurative complications.

• Acute rheumatic fever
• Acute glomerulonephritis.

Question 2. Virulence factors of streptococci.
Answer:

Question 3. Write briefly on gram-positive cocci.
Answer:

Gram-positive cocci are those that resist decolorization and retain primary stain-appearing violet.

Examples:

Question 4. Alpha hemolytic streptococci.
Answer:

• Produces greenish discoloration with partial hemolysis around colonies
• The zone of lysis is small
• There is the presence of unlysed erythrocytes.
• They are normal commensals in the throat and may cause opportunistic infections rarely
• They are classified into species by physiological and biochemical properties
• Example: viridian’s group of streptococcus

Staphylococcus Important Notes

1. Toxins produced by staphylococci and diseases caused by them

2. Classification of streptococci

• Alpha hemolytic streptococci
• Beta hemolytic streptococci
• Gamma hemolytic/ non hemolytic/ enterococcus group

3. Toxins produced by streptococci

4. Diseases caused by streptococci

• Sore throat
• Ludwig’s angina, otitis media, quinsy, cellulitis
• Erysipelas, impetigo
• Acute glomerulonephritis
• Acute rheumatic fever

5. Toxins produced by pneumococci

• Hemolysin
• Leucocidin

6. Outer membrane of gonococci consists of

• Lipopolysaccharides
• Proteins
  • Protein 1 – helps in typing of strains, forms pores on surface
  • Protein 2 – helps in adhesion
  • Protein 3 – associated with protein 1

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7. McLeod classification

• Gravis
• Intermedius
• Mitis

8. Test used for bacillus anthrax

• M Fadyean’s reaction
• String of pearls reaction
• Ascolis thermoprecipitation test

9. Diseases caused by bacillus anthrax

• Hide Porter’s disease
• Pulmonary anthrax
• Malignant pustule

10. Toxins produced by clostridium tetani

• Tetanolysin
• Tetanospasmin

11. Antigens of salmonella typhi

• H antigen
• O or somatic antigen
• Vi or virulence antigen

12. Types of E.coli

• Enteropathogenic E.coli
• Enterotoxigenic E.coli
• Entero aggregative E.coli
• Enteninvasive E.coli
• Enterohaemorrhagic E.coli

13. Classification of vibrios

• Halophilic vibrios
• V. vulnibicus
• V. alginolyticus
• V. parahemolyticus
• Non halophilic vibrios
• V. cholera
• V. mimicus

14. Diseases caused by Pseudomonas aeruginosa

• Infections in burns
• Iatrogenic meningitis
• Nosocomial infection
• Blue pus
• Bed sores
• Shanghai fever

15. Tests used for mycobacterium tuberculosis

• Catalase peroxidase
• Microscopy
• Petroff s method
• Montouxtest

16. Classification of leprosy

• Lepromatous leprosy
• Tuberculoid leprosy
• Dimorphous leprosy
• Indeterminate
• Pure neuritic

17. Lepra reaction

• Type 1 – reversal reaction
• Type 2 – erythema nodosum leprosum

Staphylococcus Long Essays

Question 1. Describe the morphology, staining characters, and pathogenicity of Staphylococcus. Add a note on laboratory diagnosis of staphylococcal infections.
Answer:

Staphylococcus Morphology:

• Staphylococcus are
  • Gram-positive
  • Non-motile
  • Non-sporing.
  • Non-capsulated
  • Aerobic and normally facultative anaerobic.
• Shape: spherical cocci.
• Size: approx 1 micrometer in diameter.
• Arrangement: Arranged in grape-like clusters.
• This arrangement is due to cell division occurring in three planes.
• They may be found singly, in pairs, and in short chains of 3 – 4 cells.

Staphylococcus Staining characters:

• Staphylococci are gram-positive cocci.
• On gram-staining:
  • They resist decolorization with acetone.
  • Retain the color of the primary stain.
  • Appears violet in color in pink background.

Staphylococcus Pathogenicity:

Staphylococcus produces two types of diseases.

1. Infections – In it.

2. Intoxications.

In it, the disease is caused by the toxins produced by bacteria.

Staphylococcal diseases:

Laboratory Diagnosis:

The specimen to be collected depends on the type of lesion.

Specimen

• Pus
• Sputum
• CSF
• Blood
• Suspected food

Infections

• Suppurative lesions
• Respiratory infections
• Meningitis
• Septicaemia
• Food poisoning

1. Direct microscopy.

• Gram staining of the smear shows gram-positive cocci arranged in clusters.

2. Culture.

• The inoculated media used are incubated at 37oC for 18 – 24 hours.
• The cultural media used are.

3. Biochemical reaction

• Catalase test – positive.
  • It distinguishes Staphylococcus from streptococcus
• Coagulase test – positive
• Mannitol fermentation – produces acid without gas
• Gelatin fermentation – positive.
• Tellurite reduction – positive.
• Production of enzyme phosphatase and deoxyribonuclease – positive.

4. Bacteriophage typing.

• Trace the source of staphylococcus.

5. Antibiotic susceptibility.

• Determined by Stokes method.

6. Serological tests.

• Helps to diagnose hidden deep infections.
• Also, titre more than 2 units/ml with rising titre diagnose deep infections.

Question 2. Classify staphylococci. Describe the morphology, cultural characteristics, and reactions of staphylococcus aureus. Describe the pathological lesions caused by staphylococci.
Answer:

Staphylococci Classification:

• Based on pigment production and virulence.

• Based on coagulase production.
• Coagulase positive – St. Aureus.
• Coagulase-negative – other staphylococci

Morphology Cultural characteristics:

Staphylococci usually grow readily within a temperature range of 10 – 42°C with an optimal temperature of 37°C and pH 7.4 – 7.6.

Morphology Reactions:

Staphylococcus aureus undergoes following, reaction.

• Catalase positive.
• Oxidase negative.
• Fermentation of sugar.
  • It ferments sugar without gas.
  • This helps to distinguish staphylococcus aureus from. St. Epidermidis.
• Causes beta type of hemolysis.
•  Produces.
  • Coagulase.
  • Phosphatase.
  • Enzyme deoxyribonuclease.
• Reduction of tellurite occurs.

Staphylococcus Short Essays

Question 1. Name enzymes produced by staphylococcus aureus.
Answer:

Enzymes:

Staphylococcus Short Question And Answers

Question 1. Antigenic structure of staphylococci.
Answer:

Antigenic structure of staphylococci composed on.

Question 2. Coagulase test.
Answer:

The coagulase test is the standard criterion for the identification of staphylococcus aureus isolates.

It is done by two methods.

1. Slide coagulase test.

• It detects bound coagulase.
• It gives results parallel to the tube test.
• In this method, a few colonies of bacteria re emulsified in a drop of normal saline on a clean glass slide.
• It is mixed with a drop of undiluted rabbit or human plasma.

2. Tube coagulase.

• It detects free coagulase.
• In this method, 0.1 ml of an overnight broth culture or an agar culture suspension of the organism is mixed with 0.5 ml of a 1 in 5 dilutions of human or rabbit plasma.
• Diluted plasma in another tube is used as a control.
• Plasma clots in case of positive reaction.

Question 3. Bacteriophage typing.
Answer:

• Bacteriophage typing is important in epidemiological studies of staphylococcal infections.
• Strains of S. aureus may be distinguished by their susceptibility to different bacteriophages.
• An internationally accepted set of 23 bacteriophages is employed.

Bacteriophage typing Method

Centre in India:

Department of Microbiology, Moulana Azad Medical College, New Delhi.

Question 4. Enumerate pyogenic organisms.
Answer:

Pyogenic Organism:

1. Staphylococcus Aureus – Gram-positive cocci.
2. Streptococcus pyogenes – Gram-positive cocci.
3. Klebsiella pneumonia – Gram-negative bacilli.
4. Burkholderia mallei – Gram-negative bacilli.

Question 5. Treatment of staphylococcal infections.
Answer: