ESBLs

Extended-spectrum beta-lactamases (ESBLs) are enzymes produced by some Gram-negative bacteria that confer resistance to many beta-lactam antibiotics. They hydrolyze penicillins and extended-spectrum cephalosporins, including cefotaxime and ceftazidime, reducing antibiotic activity. ESBLs are typically inhibited by beta-lactamase inhibitors such as clavulanic acid, though inhibition is not universal. ESBLs usually do not efficiently degrade cephamycins (for example, cefoxitin), but resistance can arise when other mechanisms are present.

The most common ESBL families are TEM, SHV, and CTX-M, with CTX-M now the most prevalent worldwide. ESBL genes are commonly carried on plasmids and other mobile genetic elements, enabling rapid spread between Enterobacterales and other Gram-negative species.

Infections caused by ESBL-producing organisms most often involve Escherichia coli and Klebsiella pneumoniae, but can occur with other Gram-negative bacteria. Clinically, ESBL infections are associated with increased morbidity and mortality, longer hospital stays, and limited antibiotic options. They are commonly implicated in urinary tract infections, intra-abdominal infections, bloodstream infections, and hospital-acquired pneumonia, particularly in patients with prior antibiotic exposure or healthcare contact.

Diagnosis and treatment: Detection relies on phenotypic methods such as reduced susceptibility to third-generation cephalosporins that is restored by clavulanate, or confirmatory tests and molecular methods identifying ESBL genes. Management depends on susceptibility testing. For severe infections, carbapenems have been the reference therapy, but options include newer beta-lactam/beta-lactamase inhibitor combinations (for example, ceftazidime-avibactam, meropenem-vaborbactam, or imipenem-relebactam) depending on the organism and local resistance patterns. Antimicrobial stewardship and infection-control measures are essential to limit spread.

Prevention and public health: Hospitals employ active surveillance, contact precautions for patients colonized or infected with ESBL producers, hand hygiene, environmental cleaning, and judicious antibiotic use to reduce selection pressure and limit transmission.