Clostridium Questions and Answers

Q: Nagler's reaction is useful for the identification of

Correct answer: C perfringensNagler’s reaction demonstrates alpha toxin, the lecithinase of C. perfringens. The organism is streaked on a plate of egg yolk or human serum agar, half of which has been spread with antitoxin. Opalescence appears in the medium around the growth on the untreated half, where the lecithinase has split the lipoprotein, and is absent on the half where antitoxin has neutralised it. The specific inhibition is what makes the test identifying rather than merely suggestive.

Q: A 10-year old boy following a road traffic accident presents to the casualty with a contaminated wound over the left leg. He has received his completed primary immunization before preschool age and received a booster of DT at school entry age. All of the following can be done except:

Correct answer: Injection of human antiserumThe boy has had a complete primary course and a booster at school entry, so he is immune and needs only a booster dose of toxoid for this contaminated wound; passive immunisation adds nothing and carries the risks of a serum product. The other three are all appropriate: tetanus toxoid, antibiotics, and above all thorough debridement and cleaning, which removes the devitalised tissue in which clostridia would otherwise grow.

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: True about clostridium tetani:

Correct answer: Drum stick appearanceC. tetani is a Gram-positive obligate anaerobe carrying a terminal spherical spore that swells the rod into the drumstick shape. Two of the options are true of it - it is Gram positive, and it shows the drumstick - but the drumstick is the distinguishing morphological feature asked for here, the Gram reaction being shared with the whole genus. It certainly does not grow aerobically, and it is not Gram negative.

Q: Nagler’s reaction is shown by:

Correct answer: Cl. PerfringensNagler’s reaction demonstrates the lecithinase activity of alpha toxin. C. perfringens is grown on egg yolk agar half of which carries antitoxin: opalescence appears around the growth on the untreated half where the lecithin has been split, and is absent where antitoxin has neutralised the enzyme. It is the specific inhibition by antitoxin that makes the test conclusive.

51.

Nagler's reaction is useful for the identification of

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

Answer: B

Correct answer: C perfringens

Nagler’s reaction demonstrates alpha toxin, the lecithinase of C. perfringens. The organism is streaked on a plate of egg yolk or human serum agar, half of which has been spread with antitoxin. Opalescence appears in the medium around the growth on the untreated half, where the lecithinase has split the lipoprotein, and is absent on the half where antitoxin has neutralised it. The specific inhibition is what makes the test identifying rather than merely suggestive.

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52.

A 10-year old boy following a road traffic accident presents to the casualty with a contaminated wound over the left leg. He has received his completed primary immunization before preschool age and received a booster of DT at school entry age. All of the following can be done except:

A.Injection of TT
B.Injection of human antiserum
C.Broad-spectrum antibiotics
D.Wound debridement and cleaning

Answer: B

Correct answer: Injection of human antiserum

The boy has had a complete primary course and a booster at school entry, so he is immune and needs only a booster dose of toxoid for this contaminated wound; passive immunisation adds nothing and carries the risks of a serum product. The other three are all appropriate: tetanus toxoid, antibiotics, and above all thorough debridement and cleaning, which removes the devitalised tissue in which clostridia would otherwise grow.

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53.

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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54.

True about clostridium tetani:

A.It is Gram +ve
B.Drum stick appearance
C.Grows in aerobic environment
D.It is Gram -ve

Answer: B

Correct answer: Drum stick appearance

C. tetani is a Gram-positive obligate anaerobe carrying a terminal spherical spore that swells the rod into the drumstick shape. Two of the options are true of it - it is Gram positive, and it shows the drumstick - but the drumstick is the distinguishing morphological feature asked for here, the Gram reaction being shared with the whole genus. It certainly does not grow aerobically, and it is not Gram negative.

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55.

Nagler’s reaction is shown by:

A.Cl. Tetani
B.Cl. Botulinum
C.Cl. Perfringens
D.Cl. Septicum

Answer: C

Correct answer: Cl. Perfringens

Nagler’s reaction demonstrates the lecithinase activity of alpha toxin. C. perfringens is grown on egg yolk agar half of which carries antitoxin: opalescence appears around the growth on the untreated half where the lecithin has been split, and is absent where antitoxin has neutralised the enzyme. It is the specific inhibition by antitoxin that makes the test conclusive.

Discuss in Forum

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