Clostridium Questions and Answers

Q: Which of the following temperatures is suitable for the multiplication of clostridia?

Correct answer: 109 to 116 degree FC. perfringens grows fastest at about 43 to 47 degrees Celsius, that is 109 to 116 degrees Fahrenheit, and at that temperature its generation time can be under ten minutes - among the shortest of any pathogen. This is why a cooked meat dish left to cool slowly, passing through that range, is such a classic vehicle for its food poisoning, and why rapid cooling is the standard control measure.

Q: Which serovar of C. botulinum occurs mainly in the sediments of the Great Lakes?

Correct answer: EType E strains are characteristically found in the sediments of lakes and coastal waters, including the Great Lakes, and are associated with outbreaks following fish and marine products, particularly uncooked or fermented preparations. The type distribution is geographical and ecological: type A predominates in the soils of the western United States and type B in Europe, so the food history often suggests which type is involved.

Q: Patients with botulism are treated with monovalent antitoxin.

Correct answer: FalseBotulism is treated with trivalent antitoxin covering types A, B and E, since these are the three types responsible for almost all human cases and the type cannot be known when treatment must begin. Antitoxin neutralises only toxin still circulating and cannot reverse what is already bound to nerve endings, so it must be given as early as possible - with ventilatory support, which is what actually keeps the patient alive.

Q: Toxin A involved in pseudomembranous colitis is a type of _______________

Correct answer: enterotoxinClostridioides difficile produces two toxins. Toxin A is an enterotoxin, damaging the mucosa and causing fluid secretion and inflammation; toxin B is a cytotoxin, far more potent against cultured cells and the basis of the classical cell culture assay. Both glucosylate Rho GTPases, disrupting the actin cytoskeleton, and together they produce the pseudomembranes of the colitis that follows disturbance of the normal flora by antibiotics.

Q: Which of the following inactivates IgA antibodies?

Correct answer: DiphthinDiphthin is an IgA protease produced by Corynebacterium diphtheriae; by cleaving secretory IgA it disables the principal antibody defence of the respiratory mucosa and helps the organism establish itself there. Cord factor is a mycobacterial glycolipid responsible for serpentine growth and granuloma formation, neuraminidase promotes spread through mucus, and K antigens are capsular antigens that resist phagocytosis - none of them acting on IgA.

Q: Erythrasma is caused by which of the following microorganism?

Correct answer: Corynebacterium minutissimumErythrasma is a superficial infection of the skin folds - groin, axilla and toe webs - caused by Corynebacterium minutissimum. It produces well-demarcated reddish-brown scaly patches which fluoresce coral-pink under Wood’s light because of the porphyrins the organism makes, and that fluorescence distinguishes it at once from the fungal infections it resembles. Treatment is with topical or oral erythromycin.

Q: Schick Test is used for detection of which of the following disease?

Correct answer: DiphtheriaThe Schick test detects susceptibility to diphtheria. A small dose of diphtheria toxin is injected intradermally: in a person without circulating antitoxin the toxin produces local redness and induration - a positive test, meaning susceptible - while in an immune person the antitoxin neutralises it and no reaction appears. A control of heated toxin in the other arm distinguishes a true reaction from hypersensitivity to the protein.

Q: Which among the following species causes tuberculosis?

Correct answer: Mycobacterium bovisM. bovis causes tuberculosis in cattle and, through unpasteurised milk, in humans, where it classically produces intestinal and cervical lymph node disease as well as pulmonary tuberculosis indistinguishable from that caused by M. tuberculosis. It is a member of the M. tuberculosis complex, and the BCG vaccine is an attenuated strain of it. M. leprae causes leprosy, M. ulcerans the Buruli ulcer, and M. kansasii an opportunistic lung disease resembling but distinct from tuberculosis.

21.

Which of the following temperatures is suitable for the multiplication of clostridia?

A.109 to116 degree F
B.100 degree F
C.-2 to 16 degree F
D.30-40 degree F

Answer: A

Correct answer: 109 to 116 degree F

C. perfringens grows fastest at about 43 to 47 degrees Celsius, that is 109 to 116 degrees Fahrenheit, and at that temperature its generation time can be under ten minutes - among the shortest of any pathogen. This is why a cooked meat dish left to cool slowly, passing through that range, is such a classic vehicle for its food poisoning, and why rapid cooling is the standard control measure.

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22.

Which serovar of C. botulinum occurs mainly in the sediments of the Great Lakes?

Answer: C

Correct answer: E

Type E strains are characteristically found in the sediments of lakes and coastal waters, including the Great Lakes, and are associated with outbreaks following fish and marine products, particularly uncooked or fermented preparations. The type distribution is geographical and ecological: type A predominates in the soils of the western United States and type B in Europe, so the food history often suggests which type is involved.

Discuss in Forum

23.

Patients with botulism are treated with monovalent antitoxin.

A.True
B.False

Answer: B

Correct answer: False

Botulism is treated with trivalent antitoxin covering types A, B and E, since these are the three types responsible for almost all human cases and the type cannot be known when treatment must begin. Antitoxin neutralises only toxin still circulating and cannot reverse what is already bound to nerve endings, so it must be given as early as possible - with ventilatory support, which is what actually keeps the patient alive.

Discuss in Forum

24.

Toxin A involved in pseudomembranous colitis is a type of _______________

A.endotoxin
B.enterotoxin
C.cytotoxin
D.neurotoxin

Answer: B

Correct answer: enterotoxin

Clostridioides difficile produces two toxins. Toxin A is an enterotoxin, damaging the mucosa and causing fluid secretion and inflammation; toxin B is a cytotoxin, far more potent against cultured cells and the basis of the classical cell culture assay. Both glucosylate Rho GTPases, disrupting the actin cytoskeleton, and together they produce the pseudomembranes of the colitis that follows disturbance of the normal flora by antibiotics.

Discuss in Forum

25.

Which of the following inactivates IgA antibodies?

A.Cord factor
B.Diphthin
C.Neuroaminidase
D.K antigens

Answer: B

Correct answer: Diphthin

Diphthin is an IgA protease produced by Corynebacterium diphtheriae; by cleaving secretory IgA it disables the principal antibody defence of the respiratory mucosa and helps the organism establish itself there. Cord factor is a mycobacterial glycolipid responsible for serpentine growth and granuloma formation, neuraminidase promotes spread through mucus, and K antigens are capsular antigens that resist phagocytosis - none of them acting on IgA.

Discuss in Forum

26.

Erythrasma is caused by which of the following microorganism?

A.Corynebacterium diphtheriae
B.Corynebacterium ulcerans
C.Corynebacterium minutissimum
D.Listeria monocytogenes

Answer: C

Correct answer: Corynebacterium minutissimum

Erythrasma is a superficial infection of the skin folds - groin, axilla and toe webs - caused by Corynebacterium minutissimum. It produces well-demarcated reddish-brown scaly patches which fluoresce coral-pink under Wood’s light because of the porphyrins the organism makes, and that fluorescence distinguishes it at once from the fungal infections it resembles. Treatment is with topical or oral erythromycin.

Discuss in Forum

27.

Schick Test is used for detection of which of the following disease?

A.Diphtheria
B.Tuberculosis
C.Erythrasma
D.Botulism

Answer: A

Correct answer: Diphtheria

The Schick test detects susceptibility to diphtheria. A small dose of diphtheria toxin is injected intradermally: in a person without circulating antitoxin the toxin produces local redness and induration - a positive test, meaning susceptible - while in an immune person the antitoxin neutralises it and no reaction appears. A control of heated toxin in the other arm distinguishes a true reaction from hypersensitivity to the protein.

Discuss in Forum

28.

Which among the following species causes tuberculosis?

A.Mycobacterium leprae
B.Mycobacterium kansasii
C.Mycobacterium bovis
D.Mycobacterium ulcerans

Answer: C

Correct answer: Mycobacterium bovis

M. bovis causes tuberculosis in cattle and, through unpasteurised milk, in humans, where it classically produces intestinal and cervical lymph node disease as well as pulmonary tuberculosis indistinguishable from that caused by M. tuberculosis. It is a member of the M. tuberculosis complex, and the BCG vaccine is an attenuated strain of it. M. leprae causes leprosy, M. ulcerans the Buruli ulcer, and M. kansasii an opportunistic lung disease resembling but distinct from tuberculosis.

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29.

The following statements are true regarding Clostridium perfringens except:

A.It is the commonest cause of gas gangrene
B.It is normally present in human feces
C.The principal toxin of C. perfringens is the alpha-toxin
D.Gas gangrene producing strains of C. perfringens produce heat resistant spores

Answer: D

Correct answer: Gas gangrene producing strains of C. perfringens produce heat resistant spores

This is the exception. It is the food poisoning strains of type A whose spores are heat resistant, surviving cooking to germinate as the food cools; the gas gangrene strains produce heat-sensitive spores. The other three statements are true: C. perfringens is much the commonest cause of gas gangrene, it is a normal inhabitant of the human intestine, and its principal toxin is the alpha toxin, a lecithinase.

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30.

Regarding gas gangrene one of the following is correct:

A.It is due to Clostridium botulinum infection
B.Clostridial species are gram-negative anaerobes forming spores
C.The clinical features are due to the release of protein endotoxin
D.Gas is invariably present in the muscle compartments

Answer: D

Correct answer: Gas is invariably present in the muscle compartments

Gas in the muscle compartments, detectable as crepitus or on radiograph, is the defining feature that names the disease and is produced by the saccharolytic fermentation of the clostridia. The other statements are all wrong: gas gangrene is caused by C. perfringens and other clostridia, not C. botulinum; clostridia are Gram-positive spore formers; and the clinical features are due to exotoxins, chiefly alpha toxin, endotoxin being a feature of Gram-negative organisms.

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