Clostridium Questions and Answers

Q: Clostridium botulinum food poisoning is due to

Correct answer: preformed toxinClassical botulism is an intoxication and not an infection: the organism grows in improperly preserved food, produces its toxin there, and the toxin is swallowed ready-made. The organism itself need not colonise the gut at all, and there is no fever and no diarrhoea. That is why the incubation is short, 12 to 36 hours, and why boiling the food before eating - the toxin being heat-labile - prevents the disease. Infant botulism and wound botulism are the two exceptions, in which the organism does grow in the host.

Q: Drumstick appearance is characteristic of

Correct answer: all of theseA drumstick appearance means a spherical spore at the very end of the bacillus, swelling it to a diameter greater than the rod. Three clostridia show it: C. tetani, C. tetanomorphum and C. sphenoides. Since morphology alone therefore cannot identify C. tetani, the diagnosis rests on culture characteristics, the swarming growth on blood agar, and toxin demonstration.

Q: Blackening of meat in cooked meat broth is through

Correct answer: C histolyticumC. histolyticum is the most strongly proteolytic of the clostridia, and in cooked meat broth it digests the meat particles, turning them black and eventually dissolving them, with a foul putrefactive odour. C. sporogenes does the same. The saccharolytic species, chiefly C. perfringens, redden the meat instead without digesting it, so the two reactions divide the genus at a glance.

Q: Typical drumstick appearance of bacilli is generally seen in

Correct answer: C tetaniAmong the four listed, only C. tetani carries a terminal spherical spore that swells the rod into the classic drumstick. C. perfringens is famous for rarely showing spores at all in clinical material, C. botulinum has subterminal oval spores, and C. histolyticum likewise. The appearance is suggestive rather than diagnostic, since C. tetanomorphum and C. sphenoides share it, but among these four it points unambiguously to C. tetani.

Q: Which of the following is or are obligate anaerobes?

Correct answer: All of theseThe entire genus Clostridium is anaerobic, lacking catalase and superoxide dismutase and therefore unable to deal with the toxic products of oxygen metabolism. C. septicum, C. novyi and C. tetani are all obligate anaerobes, C. novyi being among the most oxygen-sensitive of all and requiring particular care in culture. This is why anaerobic jars and reduced media are essential and why a negative culture never excludes a clostridial infection.

Q: Which of the following organisms produces neurotoxin as a virulence factor?

Correct answer: Clostridium tetaniTetanospasmin is the neurotoxin of C. tetani and is responsible for the whole clinical picture of tetanus; the organism itself remains localised in the wound and is barely invasive. Bacillus anthracis produces a three-component toxin acting through adenylate cyclase and a protease, Streptococcus pneumoniae produces pneumolysin, a cytolysin, and Staphylococcus aureus produces a range of toxins including enterotoxins and toxic shock syndrome toxin - none of them a neurotoxin.

Q: Booster immunizations should be given every 10 years.

Correct answer: TrueImmunity following tetanus toxoid wanes with time, so a booster is recommended every ten years to keep the antitoxin level above the protective threshold. The same interval governs wound management: a clean minor wound in someone immunised within ten years needs no further dose, while a longer gap or a contaminated wound calls for a booster, and human tetanus immunoglobulin as well if the primary course was never completed.

Q: Clostridium perfringens type A occurs as a natural flora of _____________

Correct answer: intestineC. perfringens type A is a normal inhabitant of the human and animal large intestine, and from there it reaches soil, dust and clothing. Because the source is endogenous as well as environmental, gas gangrene can follow an operation on the bowel or a compound fracture contaminated with the patient’s own faecal flora, and the same organism is the commonest cause of clostridial food poisoning.

Q: __________________ is a hyaluronidase that may aid invasiveness of C.perfringens.

Correct answer: κ toxinAmong the minor toxins of C. perfringens, mu toxin is the hyaluronidase, which breaks down the hyaluronic acid of connective tissue ground substance and so helps the infection spread through the tissue planes. Kappa toxin is the collagenase, theta toxin the oxygen-labile haemolysin, and alpha toxin the lecithinase that is the principal lethal factor. Together they explain the speed with which gas gangrene advances.

Q: What pressure of oxygen is used in the treatment involving the use of hyperbaric oxygen?

Correct answer: 3Hyperbaric oxygen for gas gangrene is given at about three atmospheres absolute, in sessions of an hour or two. The raised oxygen tension is directly toxic to the obligately anaerobic clostridia, halts further alpha toxin production, and improves the oxygenation of the marginal tissue at the edge of the lesion. It is an adjunct rather than a substitute: surgical debridement of the dead muscle and penicillin remain the essentials.

11.

Clostridium botulinum food poisoning is due to

A.invasion of bacteria in the intestine
B.preformed toxin
C.both (a) and (b)
D.none of the above

Answer: B

Correct answer: preformed toxin

Classical botulism is an intoxication and not an infection: the organism grows in improperly preserved food, produces its toxin there, and the toxin is swallowed ready-made. The organism itself need not colonise the gut at all, and there is no fever and no diarrhoea. That is why the incubation is short, 12 to 36 hours, and why boiling the food before eating - the toxin being heat-labile - prevents the disease. Infant botulism and wound botulism are the two exceptions, in which the organism does grow in the host.

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12.

Drumstick appearance is characteristic of

A.C tetanomorphum
B.C tetani
C.C sphenoides
D.all of these

Answer: D

Correct answer: all of these

A drumstick appearance means a spherical spore at the very end of the bacillus, swelling it to a diameter greater than the rod. Three clostridia show it: C. tetani, C. tetanomorphum and C. sphenoides. Since morphology alone therefore cannot identify C. tetani, the diagnosis rests on culture characteristics, the swarming growth on blood agar, and toxin demonstration.

Discuss in Forum

13.

Blackening of meat in cooked meat broth is through

A.C histolyticum
B.C perfringens
C.C tetani
D.all of these

Answer: A

Correct answer: C histolyticum

C. histolyticum is the most strongly proteolytic of the clostridia, and in cooked meat broth it digests the meat particles, turning them black and eventually dissolving them, with a foul putrefactive odour. C. sporogenes does the same. The saccharolytic species, chiefly C. perfringens, redden the meat instead without digesting it, so the two reactions divide the genus at a glance.

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14.

Typical drumstick appearance of bacilli is generally seen in

A.C perfringens
B.C botulinum
C.C tetani
D.C histolyticum

Answer: C

Correct answer: C tetani

Among the four listed, only C. tetani carries a terminal spherical spore that swells the rod into the classic drumstick. C. perfringens is famous for rarely showing spores at all in clinical material, C. botulinum has subterminal oval spores, and C. histolyticum likewise. The appearance is suggestive rather than diagnostic, since C. tetanomorphum and C. sphenoides share it, but among these four it points unambiguously to C. tetani.

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15.

Which of the following is or are obligate anaerobes?

A.C septicum
B.C novyi
C.C tetani
D.All of these

Answer: D

Correct answer: All of these

The entire genus Clostridium is anaerobic, lacking catalase and superoxide dismutase and therefore unable to deal with the toxic products of oxygen metabolism. C. septicum, C. novyi and C. tetani are all obligate anaerobes, C. novyi being among the most oxygen-sensitive of all and requiring particular care in culture. This is why anaerobic jars and reduced media are essential and why a negative culture never excludes a clostridial infection.

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16.

Which of the following organisms produces neurotoxin as a virulence factor?

A.Bacillus anthracis
B.Clostridium tetani
C.Streptococcus pneumoniae
D.Staphylococcus aureus

Answer: B

Correct answer: Clostridium tetani

Tetanospasmin is the neurotoxin of C. tetani and is responsible for the whole clinical picture of tetanus; the organism itself remains localised in the wound and is barely invasive. Bacillus anthracis produces a three-component toxin acting through adenylate cyclase and a protease, Streptococcus pneumoniae produces pneumolysin, a cytolysin, and Staphylococcus aureus produces a range of toxins including enterotoxins and toxic shock syndrome toxin - none of them a neurotoxin.

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17.

Booster immunizations should be given every 10 years.

A.True
B.False

Answer: A

Correct answer: True

Immunity following tetanus toxoid wanes with time, so a booster is recommended every ten years to keep the antitoxin level above the protective threshold. The same interval governs wound management: a clean minor wound in someone immunised within ten years needs no further dose, while a longer gap or a contaminated wound calls for a booster, and human tetanus immunoglobulin as well if the primary course was never completed.

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18.

Clostridium perfringens type A occurs as a natural flora of _____________

A.stomach
B.mouth
C.intestine
D.eyes

Answer: C

Correct answer: intestine

C. perfringens type A is a normal inhabitant of the human and animal large intestine, and from there it reaches soil, dust and clothing. Because the source is endogenous as well as environmental, gas gangrene can follow an operation on the bowel or a compound fracture contaminated with the patient’s own faecal flora, and the same organism is the commonest cause of clostridial food poisoning.

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19.

__________________ is a hyaluronidase that may aid invasiveness of C.perfringens.

A.alpha toxin
B.theta toxin
C.µ toxin
D.κ toxin

Answer: C

Correct answer: κ toxin

Among the minor toxins of C. perfringens, mu toxin is the hyaluronidase, which breaks down the hyaluronic acid of connective tissue ground substance and so helps the infection spread through the tissue planes. Kappa toxin is the collagenase, theta toxin the oxygen-labile haemolysin, and alpha toxin the lecithinase that is the principal lethal factor. Together they explain the speed with which gas gangrene advances.

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20.

What pressure of oxygen is used in the treatment involving the use of hyperbaric oxygen?

A.1
B.5
C.100
D.3

Answer: D

Correct answer: 3

Hyperbaric oxygen for gas gangrene is given at about three atmospheres absolute, in sessions of an hour or two. The raised oxygen tension is directly toxic to the obligately anaerobic clostridia, halts further alpha toxin production, and improves the oxygenation of the marginal tissue at the edge of the lesion. It is an adjunct rather than a substitute: surgical debridement of the dead muscle and penicillin remain the essentials.

Discuss in Forum

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