Which antibiotics are commonly considered inactive against organisms producing ESBLs and thus not chosen for susceptibility testing?

Which antibiotics are commonly considered inactive against organisms producing ESBLs and thus not chosen for susceptibility testing?

• A. Aztreonam
• B. Cephalosporins
• C. Penicillin
• D. Meropenem

Answer: (B)

Extended-spectrum beta-lactamases break down many beta-lactam antibiotics, with cephalosporins being particularly affected. Because ESBLs inactivate these drugs, susceptibility testing with cephalosporins is not reliable for ESBL-producing organisms and does not provide useful guidance for therapy. Clinically, testing and treatment focus on agents that remain active against ESBL producers, especially carbapenems like meropenem. While penicillins are also inactivated by ESBLs, cephalosporins are the class most consistently considered inactive in this context, which is why they’re not typically chosen for susceptibility testing in ESBL-producing isolates.

Extended-spectrum beta-lactamases break down many beta-lactam antibiotics, with cephalosporins being particularly affected. Because ESBLs inactivate these drugs, susceptibility testing with cephalosporins is not reliable for ESBL-producing organisms and does not provide useful guidance for therapy. Clinically, testing and treatment focus on agents that remain active against ESBL producers, especially carbapenems like meropenem. While penicillins are also inactivated by ESBLs, cephalosporins are the class most consistently considered inactive in this context, which is why they’re not typically chosen for susceptibility testing in ESBL-producing isolates.