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Microbiology

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Gram Positive Bacilli

Question
42 out of 71
 

True regarding pseudomembranous colitis are all except:



A It is caused by clostridium difficile

B The organism is a normal commensal of gut

C It is due to production of phospholipase A

D It is treated by vancomycin

Ans. C It is due to production of phospholipase A

a. C. difficile is a normal member of GI flora. It is a cause of antibiotic associated colitis or pseudomembranous enterocolitis. Antibiotics like clindamycin, ampicillin have been implicated.

b. Diagnosis is by culture or detection of toxin A (enterotoxin) and toxin B (cytotoxin) in stool. The toxins can be detected by ELISA, LA, tissue culture assay, PCR or probes.

c. Drug of choice is metronidazole and vancomycin.



Type of Test

Relative Sensitivitya

Relative Specificitya

Comment

Stool culture for C. difficile

++++

+++

Most sensitive test; specificity is ++++ if the C. difficile isolate tests positive for toxin; with clinical data, is diagnostic of CDAD

Cell culture cytotoxin test on stool

+++

++++

With clinical data, is diagnostic of CDAD; highly specific but not as sensitive as stool culture

Enzyme immunoassay for toxin A or toxins A and B in stool

++ to +++

+++

With clinical data, is diagnostic of CDAD; rapid results, but not as sensitive as stool culture or cell culture cytotoxin test

Latex test for C. difficile antigen in stool

++

+++

Detects glutamate dehydrogenase found in toxigenic and nontoxigenic strains of C. difficile and other stool organisms; less sensitive and specific than other tests; rapid results

Colonoscopy or sigmoidoscopy

+

++++

Highly specific if pseudomembranes are seen; insensitive compared with other tests

Gram Positive Bacilli Flashcard List

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