Rapid testing for beta-lactamase production is recommended before initiation of antimicrobial therapy for isolates of which organism?

• A. Serratia marcescens
• B. Haemophilus influenzae
• C. Staphylococcus epidermidis
• D. Streptococcus pyogenes

Answer: (B)

Beta-lactamase production means the organism can destroy many beta-lactam antibiotics, so rapidly knowing whether the isolate makes this enzyme helps choose effective therapy from the start.

Haemophilus influenzae is classically known for frequently producing beta-lactamase, which can render ampicillin and related drugs ineffective. A quick beta-lactamase test on the isolate helps determine if a beta-lactam antibiotic will work or if a beta-lactamase inhibitor combination (like amoxicillin–clavulanate) or another agent should be used, preventing ineffective treatment and guiding empiric therapy appropriately.

The other organisms listed don’t have beta-lactamase production as the most predictive factor for initial therapy in the same way. Streptococcus pyogenes is usually susceptible to penicillin, so beta-lactamase testing isn’t routinely needed. Staphylococcus epidermidis can produce penicillinase in some cases, but management isn’t driven primarily by this test alone. Serratia marcescens can have beta-lactamase-related resistance, but rapid beta-lactamase testing isn’t as routinely applied to guide initial therapy for it compared with Haemophilus influenzae.