A gram-positive Bacillus, which is c-hemolytic on 5% sheep blood agar, produces a wide zone of lecithinase on egg yolk agar, is nonmotile, and was isolated from the stool of a patient with abdominal pain and watery diarrhea. Because of the patient's existing immunocompromised state, the physician administered penicillin as the antibiotic therapy. The patient's condition did not improve after 7
days of treatment. Which one of the following statements explains the reason for the antibiotic failure?
a. The course was too abbreviated and should be given for 14 days.
b. The patient may be allergic to penicillin and its therapeutic effects.
c. Penicillin is ineffective against gram-positive organisms.
d. The organism produces c-lactamase, which renders the drug inactive.
D
B. anthracis produce c-lactamase; therefore penicillin and all derivatives would be an ineffective treatment, regardless of how long the antibiotic would be administered.
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