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Vibrio Long Essays

Question 1. Describe morphology, cultural characteristics, taxing, and laboratory diagnosis of vibrio cholera.
Answer:

Vibrio Cholera Morphology:

• Vibrio cholera is a gram-negative, non-capsulated, and non-sporing organism.
• It is motile and possesses a single polar flagellum, thus called darting motility.
• Size: 1.5 mm x 0.2 – 0.4 mm.
• Shape: curved or comma-shaped rod.

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Vibrio Cholera Cultural Characteristics:

• Vibrio cholera is strongly aerobe
• Grows within a temperature range of 16-40°C and alkaline pH of 8.2

Vibrio bacteria

Vibrio Cholera Toxins:

• Vibrio cholera produces enterotoxin known as cholera toxin (CT)
• It is heat-labile
• Protein in nature.
• Molecular weight – 90,000
• It has two fractions.
  • A (active) subunit – one.
  • B (binding) subunit – five.
• Its production is determined by phage integrated with bacterial chromosomes.

Vibrio Cholera Mechanism:

Laboratory Diagnosis:

1. Direct Microscopy.

• Not reliable.
• Characteristic motility of the vibrios is demonstrated by dark field or phase contracts microscope.

2. Culture.

• Nutrient agar.
  • Shows moist, translucent, round disc colonies.
• Selective media – Monsur’s GTTA media.
  • Shows small, translucent colonies with a greyish-black center and turbid halo.
• Macconkey’s agar media.
  • Shows initially colorless colonies which later become reddish.

3. Agglutination Test

• Colonies from selective media are picked up with a straight wire and tested by slide agglutination with cholera 0 subgroup I serum.
• If positive, the agglutination test is repeated using monospecific Ogawa and Inaba sera for serotyping.

4. Serological Tests – Includes.

• Agglutination using live or killed vibrio suspension.
• Indirect haemagglutination.
• Vibriocidal test.
• Antitoxin assay.

5. Biochemical Test.

• Fermentation of glucose, mannitol, maltose, sucrose.
• Indole positive.
• Reduction of nitrates.
• Catalase and oxidase positive. Voges – Broskauer negative.

Vibrio morphology

Vibrio Short Essays

Question 1. Cholera.
Answer:

Cholera Etiology:

• Cholera is caused by vibrio cholera.
• The route of infection is contaminated food and water.
• Alkaline pH in the stomach and intestine appears to be more easily infected.

Cholera Pathogenesis:

Cholera Features:

• Diarrhea is the major symptom.
• Feces contain epithelial cells, mucus, and a large number of V. Cholera.
• Profuse watery diarrhea – rice water stools occur.
• In severe cases, there may be one liter of fluid loss each hour.
• Abdominal pain.
• Death due to electrolyte abnormalities and fluid loss.

Treatment, Prevention, And Control:

• Intravenous administration of fluids.
• Oral administration of a solution containing glucose and electrolytes.
• Antibiotics.
  • Doxycycline – In adults.
  • Sulphamethethoxazole – In children.
  • Furazolidone – In pregnant women.
• Improved – hygiene.
• Water purification, immunization.

Vibrio characteristics

Vibrio Short Question And Answers

Question 1. Whooping Cough.
Answer:

Whooping cough is predominantly a childhood disease.

Whooping Cough Causative Agents:

• B. Pertusis – 95% cases.
• B. Parapertusis – 5% cases.
• B. Bronchiosepetica – 0.1% cases.

Whooping Cough Features:

• Incubation period – 1 – 2 weeks.
• Infection is transmitted by droplets.
• Diseases usually last for 6 – 8 weeks.
• It consists of 3 stages.

1. Catarrhal.

• Clinical diagnosis is difficult.

2. Paroxysmal.

• Whooping cough occurs.

3. Convalescent.

• Frequently and severity of coughing decreases.

Whooping Cough Complications:

• Subconjunctival hemorrhage.
• Subcutaneous emphysema.
• Bronchopneumonia.
• Convulsions, coma.

Whooping Cough Prophylaxis:

• Pertussis vaccine is given.
• Three injections at intervals of 4 – 6 weeks are given before the age of 6 months.
• A booster dose is given at the end of the first year.

Vibrio cholerae pathogenesis

Question 2. Castaneda’s method of culture.
Answer:

Castaneda’s is used for Brucella.

Culture Composition:

• It contains:
  • Liquid media – trypticase soy broth.
  • Solid media – trypicase soy agar.

Culture Method:

• Blood is inoculated into liquid media in a bottle.
• Incubate it in an upright position.
• The bottle is tilted and subcultured by solid media.
• Incubate it again in an upright position.

Salmonella Long Essays

Question 1. Describe etiopathogenesis and clinical features and lab diagnosis of enteric fever.
Answer:

Enteric fever:

• Etiopathogenesis:
  • Enteric Fever Includes:
    • Typhoid fever – caused by salmonella typhi.
    • Paratyphoid fever – caused by salmonella paratyphi.

Virulence Factors:

1. Endotoxin.

• Causes diverse toxic manifestations of enteric fever.

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2. Exotoxin – enterotoxin.

3. Capsule.

• Has anti-phagocytic activity.

Enteric Fever Clinical features:

• The incubation period is 7 – 14 days.
• Route of infection – contaminated food and water.

1. Typhoid Fever – Its Manifestations Include.

• Gradual illness
• Headache
• Anorexia
• Congestion of mucous membrane.
• Hepatosplenomegaly.
• Step-ladder pyrexia.
• Relative bradycardia.
• Leucopenia.
• Skin rashes called ‘Rose-spots’ appear during the second or third week.

Salmonella morphology

2. Paratyphoid Fever.

• Symptoms are milder than typhoid fever.
• Septicaemia with suppurative complications occurs.

Lab Diagnosis Of Enteric Fever:

1. Isolation Of Bacilli.

• For isolation of bacteria, specimens are obtained from blood, feces, urine, aspirated duodenal fluid, bile, bone marrow or rose spot.
• These specimens are then cultured.

2. Demonstration Of Antibodies.

• Widal Test
  • It is an agglutination for the detection of agglutinins H and 0 in patients with enteric fever

Salmonella characteristics

• Widal Test Method:
  • Equal volumes (0.4 ml) of serial dilutions of serum from 1:10 to 1: 640 and H and 0 antigens are mixed.
  • One control tube containing antigen and normal saline is used.
  • All these tubes are incubated in a water bath at 37°C.
• Widal Test Results:

• Widal Test Interpretation:

3. Demonstration of Circulating Antigen.

• Done by counterimmunoelectrophoresis and ELISA.

Salmonella Short Essays

Question 1. Diseased caused by salmonella.
Answer:

Salmonella pathogenesis

Question 2. Antigenic structure of salmonella.
Answer:

Salmonella possesses three types of antigens.

Pneumococcus Short Essays

Question 1. Morphology and cultural characteristics of pneumococci.
Answer:

Pneumococci Morphology:

• Pneumococci are gram-positive, alpha-hemolytic organisms.
• Size – small, 1 micrometer in diameter.
• Shape – slightly elongated.
• Each coccus has one end broad or rounded and other pointed.
• They are arranged in pairs.
• This shows a flame-shaped or lanceolate appearance.
• They have large polysaccharide capsules.
• They are non-motile and non-sporing.

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Pneumococci  Cultural Characteristics:

• They are aerobes and facultative anaerobes.
• The optimum temperature for growth is 37°C and pH 7.8

Pneumococcus characteristics

Pneumococcus Short Question And Answers

Question 1. C-reactive proteins (CRP).
Answer:

C-reactive protein is an abnormal protein that precipitates with the somatic C antigen of pneumococci.

• C-reactive protein is not an antibody produced as a result of pneumococcal infection but it is an acute phase substance produced in hepatocytes.
• C-Reactive Protein appears in.
  • Acute sera of cases of pneumonia.
  • Some other pathological conditions.
• C-Reactive Protein disappears during convalescence.

C-Reactive Proteins Production:

• Its production is stimulated by.
• Bacterial infections.
• Inflammation.
• Malignancies.
• Malignancies.
• Tissue destruction.

C-Reactive Proteins Use:

• As an index of the response of treatment in rheumatic fever.

C-Reactive Proteins Test:

• C-Reactive Proteins are tested by passive agglutination using latex particles coated with an anti-CRP antibody.

Question 2. Lab investigations of pneumococci.
Answer:

Pneumococcus infection

Question 3. Mention the difference between pneumococci and streptococcus viridians.
Answer:

Pneumococcus pathogenesis

Question 4. Media used for gonococci.
Answer:

Gonococci Are Aerobic Organisms.

• They grow best at a temperature of 35 – 36oC in the presence of 5 – 10 % C02 and at pH 7.2 – 7.6
• The cultural media used are

1. Enriched Media.

• It includes chocolate agar and blood agar media.
• Colonies obtained are small, round, convex, grey, and translucent.

2. Selective Media – Thayer Martin Media.

• It inhibits most contaminants.

Corynebacterium

Question 1. Describe the morphology, cultural characteristic, and laboratory diagnosis of Corynebacterium diphtheria.
Answer:

Corynebacterium Diphtheria:

• Morphology:
  • C. Diphtheria bacillus are thin slender rods.
  • Corynebacterium Diphtheria are gram-positive bacilli.
  • Corynebacterium Diphtheria are pleomorphic, nonsporting, non-motile, and non-capsulated.
  • Corynebacterium Diphtheria Size – approx 3-6 pm x 0.6 – 0.8 pm.
  • Corynebacterium Diphtheria show clubbing at one or both ends.
  • Corynebacterium Diphtheria have intracellular polyphosphate granules known as metachromatic or volutin or Babes-Ernst granules usually situated at the poles of bacilli.
  • Corynebacterium Diphtheria are arranged in pairs or small groups.
  • Corynebacterium Diphtheria frequently remains attached after division, which gives them Chinese letter or cuneiform arrangement.
  • The granules represent energy storage depots.

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Corynebacterium Diphtheria Cultural Characteristics:

• C. Diphtheria grows at a temperature of 37°C and pH – 7.3.

Corynebacterium diphtheriae morphology

Corynebacterium Laboratory Diagnosis:

1. Corynebacterium Direct Microscopy.

• Gram staining.
  • Shows gram-positive bacilli.
• Albert staining.
  • Shows beaded slender green rods in a typical Chinese letter pattern.

2. Corynebacterium Culture.

• Loeffler’s serum slope.
  • Growth appears within 6.8 hours of it
• Tellurite blood agar.
  • Incubated at 37°C for at least 48 hours.
• Blood agar.
  • Differentiate streptococcal or staphylococcal pharyngitis.

3. Corynebacterium Biochemical Reactions.

• Corynebacterium ferments carbohydrates like glucose and maltose.
• Corynebacterium reduces NO3.
• Corynebacterium is catalase-positive and oxidase-negative.

4. Corynebacterium Virulence Test: It demonstrates its toxicity.

1. In Vivo Tests:

• Subcutaneous Test:
  • Subcutaneous Methods:
    • Growth from an overnight culture on Loeffler’s slope is emulsified in 2 – 4 ml broth.
    • 0.8 ml of it is injected subcutaneously into two guinea pigs.
    • One of the pigs is protected with prior administration of 500 units of diphtheria antitoxin.
  • Subcutaneous Result:
    • Virulent strains cause the death of unprotected animals within 4 days.
• Intracutaneous Test:
  • Intracutaneous Method:
    • Broth emulsion is injected intracutaneously of about 0.1 ml into two guinea pigs.
    • One of them is protected with 500 units of diphtheria antitoxin – control animal.
    • The test animal is protected with 50 units of diphtheria antitoxin.
  • Intracutaneous Result:
    • Virulent strain causes.
    • Inflammatory reaction at the site of injection which progresses to necrosis in 48 – 72 hours in test animals.
    • No change – in control animal.

2. In Vitro Tests:

• Eleck’s Get Precipitation Test.
  • It is an in vitro immunodiffusion test.
    • Eleck’s Get Precipitation Method:
      • A rectangular strip of filter paper impregnated with diphtheria antitoxin is placed on the surface of a 20% horse serum agar while the medium is still fluid.
      • The surface is dried.
      • Once the agar is set, narrow streaks of the test strains are made at a right angle to the filter paper strip.
      • A positive and negative control is set.
      • The plate is incubated at 37°C for 24 – 48 hours.
    • Eleck’s Get Precipitation Result:
      • Virulent strains produce arrowhead lines of precipitation where the bacterial toxin meets with the antitoxin in optimum concentration.

2. Tissue Culture.

• Tissue Culture demonstrates the toxigenicity of C. diphtheria.
• The toxins produced diffuse into the cells below and kill them.

Corynebacterium diphtheriae characteristics

Question 2. Describe the morphology, pathogenesis, and immunization of Corynebacterium diphtheria.
Answer:

Immunization Of Corynebacterium Pathogenesis:

• The incubation period in diphtheria is 3 – 4 days or maybe as short as 1 day.
• It is most commonly seen in children of 2 – 10 years.
• The sites of infection are:
  • Faucial – common.
  • Laryngeal
  • Nasal
  • Conjunctival
  • Otitic
  • Vulvovaginal
  • Cutaneous.
• It causes local as well as systemic effects.
• Cutaneous diphtheria may be present as a simple pustule or chronic non-healing ulcer.

1. Immunization Of Corynebacterium Local Effects:

2. Immunization Of Corynebacterium Systemic Effects:

• Diphtheria toxin diffuses into the bloodstream and causes toxemia.
• It acts systematically on the cells of cardiac tissue, adrenal, and nerve endings.
• Complications associated with tissue damage at.
  • Heart – Cardiac dysfunction, myocarditis, and circulatory shock.
  • Nervous System – Demyelination, paralysis of throat muscle, and polyneuritis.

Immunization:

1. Active Immunization:

• It is started at 6 weeks of age by toxoid in combination with tetanus toxoid and pertussis vaccine (DPT].
• It is given by intramuscular route.
  • First dose      – 6 weeks
  • Second dose – 10 weeks
  • Third dose     – 14 weeks
  • Booster dose   – 18 months and 5 years

2. Passive Immunization.

• It is an emergency measure
• It consists of subcutaneous administration of 500 – 1000 units of antitoxin or antidiphtheric serum (ADS).
• Used in susceptible exposed to infection.

3. Combined Immunization.

• It should be given to all persons receiving ADS as prophylactic measures.
• It consists of an alum-containing preparation like an alum-precipitated toxoid.

Corynebacterium diphtheriae pathogenesis

Corynebacterium Short Question And Answers

Question 1. Name two media used for the cultivation of diphtheria.
Answer:

Media used for the cultivation of diphtheria are.

1. Loeffler’s serum slope.
2. Tellurite blood agar.
3. Hiss’s serum water.

Question 2. Name different species of the genus corynebacterium.
Answer:

Various species of the genus Corynebacterium are:

1. C. Diphtheria.
2. C. ulcerans.
3. C. Minutissimum.
4. C. Tenuis.
5. C. Pseudodiphtheriticum.
6. C. Parvum.

Corynebacterium diphtheriae diagnosis

Question 3. Staining Of Diphtheria.
Answer:

On staining of diphtheria -with Albert’s stain.

1. Bacilli – looks green.
2. Granules – Appear bluish-black.

Question 4. Types of C.diphtheria.
Answer:

Based on colony morphology, there are 3 types of C. Diphtheria they are as follows.

Enterobacteriaceae Short Question And Answers

Question 1. Name four groups of E-coli causing diarrheal diseases.
Answer:

Groups Of E-coli Causing Diarrhoea:

1. Enteropathogenic E-coli [EPEC]

• Affects infants.

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2. Enterotoxigenic E-coli [ETEC]

• Causes diarrhea in children.

3. Enteroinvasive E-coli [EIEC]

4. Enterohaemorrhage E-coli [EHEC]

• Affects infants and young children.

5. Enteroaggregative E-coli [EAEC]

Enterobacteriaceae classification

Question 2. Name bacteria causing urinary tract infection and what is significant bacteriuria.
Answer:

Bacteria Causing Urinary Tract Infection:

1. Gram Negative Bacilli.

• E-coli.
• Klebsiella sp.
• Pseudomonas aeruginosa.

2. Gram Positive Cocci.

• Enterococci.
• St. Aureus.

3. Miscellaneous:

• M. Tuberculosis.
• Salmonellae.
• St. Pyogenes.

Significant Bacteriuria:

• Kass gave a criterion for active bacteriuria.

Enterobacteriaceae characteristics

Question 3. Enterotoxin.
Answer:

They are produced by enterotoxigenic strains of E.coli.

They Are:

1. Heat labile toxin (LT)
2. Heat-stable toxin (ST)

Non-Sporing Anaerobes Short Essays

Question 1. Lactobacillus.
Answer:

Lactobacilli are non-sporing, anaerobic, Gram-positive bacilli.

• Lactobacilli are acidophilic and grow best at pH 5 or less.
• Lactobacilli show bipolar and barred staining.
• Lactobacilli are normally present in

1. Mouth.

• Lactobacilli cause dental caries.
• They form lactic acid by fermentation of sugar which destroys enamel and dentin.

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2. Intestine.

• L-acidophilus synthesize vitamins such as biotin, B₁₂, K

3. Vagina.

• Lactobacillus is called Doderleins bacilli to ferment the glycogen deposited in the vaginal epithelial cells forming lactic acid.
• This results in highly acidic pH of the vagina.
• They protect the adult vagina from infections.

Lactobacillus Culture:

Lactobacillus grow in media enriched with glucose or blood in the presence of 5% CO₂ and at pH 6

Lactobacillus Pathogenicity:

• Lactobacilli are non-pathogenic.
• Involved in serious infections in immune-compromised individuals.
• Associated with advanced dental caries.

Non-spore-forming anaerobes

Question 2. Bacteroides.
Answer:

Bacteroides are non-sporing, non-motile, obligate anaerobes, gram-negative bacilli.

• Bacteroides possess capsular polysaccharides
• Bacteroides are pleomorphic.
• Bacteroides occur normally in the mouth, gastrointestinal, and female genital tracts.

Bacteroides Common species:

• B. Fragilis – isolated from the large intestine.
• B. Maleninogenicus – isolated from or pharynx, gut, and vagina.

Bacteroides Culture:

• Bacteroides require enriched media containing blood for growth.
• Bacteroides grow readily in brain-heart infusion agar.
• P. Melaninogenica causes black or brown-coloured colonies.
• Bacteroides result in characteristic red fluorescence when exposed to ultraviolet light.

Diseases Caused By Them:

• Peritonitis.
  • Occurs following bowel injury and pelvic inflammatory disease.
• Brain and abdominal abscess.
• Empyema.
• Periodontal disease – caused by P. Gingivalis.
• Dental root canal infections – caused by P. endodon- talis.

Non-Sporing Anaerobes Short Question And Answers

Question 1. Fusobacterium.
Answer:

Fusobacterium Morphology:

• Gram-negative bacilli.
• Long slender rods that are wide at the center and taper towards the ends.
• Non-motile.

Fusobacterium Culture:

• Fusobacterium are strictly anaerobes.
• They grow on blood agar containing neomycin and vancomycin.

Fusobacterium Pathogenicity:

• Fusobacterium are commensals in the mouth, gastrointestinal, and genitourinary tracts

Fusobacterium Causes:

• Head and neck infections.
• Dental and periodontal infections.
• Cerebral abscess.
• Intraabdominal infections.
• Osteomyelitis.
• Soft tissue infection.

Non-sporing anaerobic bacteria classification

Question 2. Antibiotics are used against anaerobic bacteria.
Answer:

1. Penicillin.
2. Tetracycline
3. Chloramphenicol
4. Metronidazole.

Question 3. Enumerate four non-sporing anaerobes.
Answer:

1. Cocci.

• Gram-positive – streptococcus.
• Gram negative – veillonella.

2. Bacilli.

• Gram positive – eubacterium, lactobacillus.
• Gram negative – bacteroides, fusobacterium.

3. Spirochaetes – Treponema, borrelia.

Non-sporing anaerobes microbiology

Question 4. Name four anaerobic bacteria.
Answer:

1. Gram positive cocci – peptococci, peptostreptococci
2. Gram negative cocci – Veillonella
3. Gram positive bacilli – Clostridium
4. Gram negative bacilli – Bacteroides, fusobacterium

Clostridium

Question 1. Discuss in detail about organisms causing gas gangrene.
Answer:

• Gas gangrene is caused by Clostridium perfringes.
• Gas gangrene is also known as Clostridium Welchii.

The Organism Causing Gas Gangrene Morphology:

• Cl. Perfringes are Gram-positive, capsulated, and non-motile bacilli.
• Size: Large, 4 – 6 pm x 1
• It has subterminal spores.

Clostridium Perfringens

The Organism Causing Gas Gangrene  Culture:

• Cl. Perfringes is anerobic.
• It grows within a temperature range of 20 – 50°C and pH -5.5-8.

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The Organism Causing Gas Gangrene Biochemical Reaction:

It undergoes the following biochemical reactions.

• Ferments glucose, lactose, sucrose and maltose.
• It is indole negative.
• It leads to stormy fermentation.

The Organism Causing Gas Gangrene Toxins:

Clostridium bacteria

Organism Causing Gas Gangrene Pathogenesis:

Clostridium Perfringens

Organisms Causing Gas Gangrene Diseases Caused By Them:

• Gas gangrene
• Food poisoning.
• Necrotising enteritis.

The Organism Causing Gas Gangrene Complications:

• Profound toxemia.
• Prostration
• Death due to circulatory failure.

The Organism Causing Gas Gangrene Laboratory diagnosis.

1. Specimens Collected Are

• Muscles – At the edge of the affected area.
• Tissue – In necrotic area.
• Exudate – In deeper parts of the wounds – in active regions.

2. Cultures:

• Aerobic and anaerobic cultures are made on fresh and heated blood agar.
• A plate of serum or egg yolk agar with C. Perfringes antitoxin spread on one half is used for Nagler re-action.
• Four tubes of Robortson’s cooked meat broth are inoculated and heated at 100oC for 5, 10, 15, and 20 min and then incubated at 45°C for 4 – 6 hours bacterial isolates are identified.

Clostridium characteristics

Question 2. Classify Clostridium. Describe lab diagnosis and prophylaxis of gas gangrene.
Answer:

Clostridium Classification:

1. Based On The Shape And Position Of Spores.

• Central or subterminal.
• C. Perfringes. o C. Botulinum
• Oval and terminal -C. Tertium.
• Spherical and terminal – C. Tetani.

2. Based On Biochemical Properties.

• Both proteolytic and saccharolytic.
  • Proteolytic – predominating – C. histolyticum, C. Botulinum.
  • Saccharolytic predominating – C. Welchii.
• Slightly proteolytic but not saccharolytic – C. Tetani.
• Saccharolytic but not proteolytic -Botulinum.
• Neither proteolytic nor saccharolytic – C. Cochlearum.

2. Based On The Disease.

• Gas gangrene – C. Welchii, C. Histolyticum
• Tetanus – C. Tetani.
• Food poisoning – C. Botulinum.
• Acute colitis – C. Difficile.

Clostridium Prophylaxis:

1. Surgical Prophylaxis.

• Prompt removal of all damaged tissue.
• Irrigation of the wound with an antiseptic solution.
• Uncompromising excision of all affected tissue.

2. Antibiotics – Includes.

• Metronidazole.
• Penicillin.
• Sulphonamide.
• Tetracycline.
• Amoxycillin.

3. Antitoxin.

• Anti-gas gangrene serum provides passive immunization.

4. Introduction of hyperbaric oxygen.

Clostridium morphology

Question 3. Describe morphology, cultural characteristics, toxins liberated, and lesions produced by clostridial stains:
Answer:

Some of the clostridial strains are as follows:

Question 4. Enumerate the various pathogenic Clostridia. Describe morphology, cultural characteristics and laboratory diagnosis of Clostridium tetani.
Answer:

Pathogenic Clostridia:

• C. Welchii.
• C. Tetani.
• C. Botulinum.
• C. Septicum.
• C. histolyticum.
• C. Bifermentans.
• C. Difficle.

Pathogenic Clostridia Morphology:

• Cl. Tetani is a gram-positive, slender bacilli.
• Size – 4 – 8 pm x 0.5 pm.
• Pathogenic Clostridia has a straight axis, parallel sides, and rounded ends.
• Pathogenic Clostridia is non-capsulated.
• Pathogenic Clostridia has spherical terminal spores which gives it a drum-stick appearance.
• Pathogenic Clostridia is motile and possesses peritrich flagella.
• Pathogenic Clostridia occurs singly and occasionally in chains.

Pathogenic Clostridia Cultural Characteristics:

• Cl. Tetani is strictly an anaerobe.
• It grows at 37°C and pH. 7.4.

1. Robertson Cooked Meat Broth.

• Growth occurs as turbidity.
• Some gas formation occurs.
• Meat is not digested but turns black on prolonged incubation.

2. Blood Agar Media.

• Produces swarming growth.

3. Horse BloodAgar Media.

• Produces alpha-hemolytic colonies.
• These develop into beta-hemolytic due to the production of hemolysin.

Clostridium Perfringens

Pathogenic Clostridia Laboratory Diagnosis:

1. Direct Microscopy.

• Gram staining shows gram-positive bacilli with a drums tick appearance.

2. Culture.

• Blood Agar Media.
  • The specimen is inoculated on one-half of the blood agar plate at 37°C for 24 – 48 hours anaerobically.
  • It shows swarming growth.
• Cooked Meat Broth (CMB)
  • The specimen is inoculated in three tubes of CMB.

• • Heating kills vegetative bacteria.
  • These tubes are incubated at 37°C and subcultured on blood agar plates for 4 days.

3. Pathogenicity Test.

• Blood agar plates are used.
• Tetanus antitoxin – 1500 units/ml is spread over one-half of the plate.
• The suspected C. Tetani strains are stab-inoculated on each half of the plate.
• This is incubated anaerobically for 2 days.

Pathogenicity Test Result:

• Toxigenic strains show hemolysis around colonies in one half of the plate which does not contain antitoxin.

4. Animal Inoculation.

• 0.2 ml of 2 – 4 days old cooked meat culture is injected into the tail of 2 mice.
• One of them that has received tetanus antitoxin – 1000 units one hour before acting as a control.

Animal Inoculation Result:

• Test Animal (Without Antitoxin)
  • Symptoms begin within 12 – 24 hours.
  • Stiffness of the tail occurs.
  • Rigidity then proceeds to one leg, another leg, the trunk, and the forelimb.
  • Death occurs within 2 days.
• Control Animal (With Antitoxin)
  • No change occurs due to neutralization of toxin with antitoxin.

Clostridium function

Clostridium Short Essays

Question 1. Immunization against tetanus
(or)
Prophylaxis of tetanus.
Answer:

1. Surgical Prophylaxis.

• Aims at the removal of foreign bodies, blood clots, etc.
• It involves procedures like simple cleansing to radical excision.

2. Antibiotic Prophylaxis.

• It destroys or inhibits tetanus bacilli.
• By this production of toxins is prevented.
• It involves the use of long-acting penicillin or erythromycin.

3. Immunization.

• Active Immunization.
  • It is achieved by tetanus toxoid which is available as a plain toxoid or adsorbed on aluminum hydroxide or phosphate (APT),
  • Three doses of 0.5 ml are given intramuscularly.

• • A booster dose is given after 10 years.
  • Tetanus toxoid is given along with diphtheria toxoid and pertussis vaccine (DPT).
    • First dose       – 6 weeks
    • Second dose  – 10 weeks
    • Third dose      – 14 weeks
    • Booster dose  – 18 months or 5 years
• Passive Immunization.
  • It is achieved by antitetanus serum (ATS) prepared from hyperimmune horses.
  • 1500 IU of it is given intramuscularly immediately after wounding.
  • It may cause hypersensitivity, to avoid it human antitetanus immunoglobulin (HTIG) is given as 250 units.
• Combined Immunization.
  • It involves the first dose of
    • Tetanus toxoid – on one arm.
    • ATS or HTIG – on another arm.
  • Second and third doses of tetanus toxoid are given at monthly intervals.

Question 2. Tetanus OR lockjaw.
Answer:

Tetanus is an acute infection of the nervous system characterized by intense activity of motor neurons and resulting in severe muscle spasms.

Clostridium Perfringens

Tetanus Etiopathogenesis:

• It is caused by an exotoxin produced by Clostridium tetani bacilli.
• This acts at the synapse of the interneurons of inhibitory pathways and motor neurons to produce a blockade of spinal inhibition.

Tetanus Clinical features:

Incubation period – 6 – 10 days.

Tetanus Treatment:

1. General Measures.

• Cardiopulmonary monitoring.
• Sedation.
• Airway maintenance.

2. Antibiotics.

• Includes antibiotics like metronidazole.

3. Antitoxin.

• HTIG is given, 3000 – 6000 units 1M

4. Prophylaxis – Includes.

• Wound debridement.
• Booster doses of tetanus toxoid.

5. Unimmunised Individuals Are Given.

• ATS – 1500 units or
• HTIG – 250 units.

Clostridium spore formation

Clostridium Short Question And Answers

Question 1. Prophylaxis and treatment of gas gangrene.
Answer:

Question 2. Toxins of Cl. Tetani.
Answer:

1. Tetanolysis.

• Heat labile
• Oxygen labile
• Causes hemolysis on blood agar.
• May act as leukotoxin.

2. Tetanospasmin.

• Heat labile.
• Oxygen stable.
• Gets rapidly destroyed by proteolytic enzymes.
• Blocks release of neurotransmitters.
• Neurotoxin.
• Responsible for manifestations of tetanus.

Question 3. Nagler’s reaction.
Answer:

Nagler’s Reaction is a cultural characteristic of C. Welchii.

Nagler’s Reaction Method:

• Cl. Welchoi is grown on a media containing.
  • 6 % agar.
  • 5 % hide’s peptic digest of sheep blood.
  • 20% human serum or 5% egg yolk.
  • Neomycin sulfate
  • It is collected in a plate, half of which contains antitoxin.
  • It is incubated at 37oC for 24 hours.

Nagler’s Reaction Result:

1. Colonies Without Antitoxin.

• Surrounded by opacity.

2. Colonies Without Antitoxin.

• Do not show any opacity.

Nagler’s Reaction Mechanism:

• Alpha toxin splits lecithin into phosphorylcholine and diglyceride.
• This lipid deposit results in opacity.

Clostridium spore formation

Question 4. Prevention and treatment of botulism.
Answer:

1. Spore Germination Prevented By

• Maintaining food in an acid pH, by use of fruit preservatives.
• Storage of food at 4°C or colder.

2. Prevention Of Infant Botulism.

• Preventing consumption of honey or food containing it in infants younger than 1 year.

Botulism Treatment:

• Administration of metronidazole or penicillin
• Trivalent botulinium antitoxin.
• Ventilatory support.

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 the same width as the bacillary body.
  • Thus, they do not cause bulging.

Read And Learn More: Microbiology Question and Answers

Bacteria Bacillus Anthracis or 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.

Bacillus morphology

Question 2. Cultivation of Bacillus Anthracis.
Answer:

Bacillus anthracis is an aerobe and facultative anaerobe.

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

Bacteria Bacillus Anthracis

Question 3. Malignant pustule.
Answer:

Malignant Pustule is a feature of cutaneous anthrax

• Site of entry
• Abraded skin.

Malignant Pustule Affected Sites Involved Are:

• Face
• Neck
• Hands
• Back

The Persons Involved Are:

• Farmers
• Persons handling dead bodies.

Bacillus classification

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.

Bacteria Bacillus Anthracis

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.

Read And Learn More: Microbiology Question and Answers

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 classification

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 O₂ Requirement.

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

2. Based On Hemolytic Properties.

Toxins Produced By Streptococci:

Streptococcus characteristics

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:

Sore Throat 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, surface proteins, and cell bound streptokinase
• Cytoplasmic membranes contain antigens that suppress 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 pyogenes

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 in 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 an 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 progresses by lactobacilli.
• Other streptococci involved are.
  • Str. Milleri.
  • Str. Sangus.
  • Str. Salivaris.
  • Str. Mitior.

Streptococcus infections

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.

Subacute Bacterial Endocarditis Prevention:

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

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:

Streptococcus structure

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

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

Gram-Positive Cocci 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