Variable beta-lactam resistance has been identified among naturally occurring Bacillus anthracis isolates; therefore penicillins should not be initially used for post-exposure prophylaxis.

Variable beta-lactam resistance has been identified among naturally occurring Bacillus anthracis isolates; therefore penicillins should not be initially used for post-exposure prophylaxis.

• A. True
• B. False
• C. Only In Some Strains
• D. Not Related

Answer: (A)

When resistance to beta-lactams varies among naturally occurring Bacillus anthracis isolates, you can’t rely on penicillins to be effective in all cases. For post-exposure prophylaxis, the aim is to use an antibiotic that is reliably active against the organism given the exposure risk, until susceptibility is known or the window of risk passes. If some strains produce beta-lactamases or have other mechanisms of resistance, penicillins may fail to prevent infection in those cases. That uncertainty means starting with penicillin for PEP could leave a gap where the bacteria can still cause disease. Instead, initial PEP should use agents with proven, broad activity against B. anthracis across most strains, such as ciprofloxacin or doxycycline. If laboratory testing later confirms penicillin susceptibility for the specific isolate, penicillin can be considered as a targeted option; otherwise, continue the non-beta-lactam therapy. This is why the statement is correct.

When resistance to beta-lactams varies among naturally occurring Bacillus anthracis isolates, you can’t rely on penicillins to be effective in all cases. For post-exposure prophylaxis, the aim is to use an antibiotic that is reliably active against the organism given the exposure risk, until susceptibility is known or the window of risk passes. If some strains produce beta-lactamases or have other mechanisms of resistance, penicillins may fail to prevent infection in those cases. That uncertainty means starting with penicillin for PEP could leave a gap where the bacteria can still cause disease. Instead, initial PEP should use agents with proven, broad activity against B. anthracis across most strains, such as ciprofloxacin or doxycycline. If laboratory testing later confirms penicillin susceptibility for the specific isolate, penicillin can be considered as a targeted option; otherwise, continue the non-beta-lactam therapy. This is why the statement is correct.