ESBL

Extended-spectrum beta-lactamases (ESBLs) are enzymes produced by some Gram-negative bacteria that confer resistance to penicillins and expanded-spectrum cephalosporins (for example cefotaxime and ceftazidime). Most ESBLs are plasmid-encoded, allowing rapid spread among Enterobacterales such as Escherichia coli and Klebsiella pneumoniae. The principal enzyme families are CTX-M, SHV, and TEM.

Clinical significance: Infections with ESBL producers are linked to higher morbidity and mortality, limited antimicrobial options, and increased healthcare costs. They are commonly acquired in healthcare settings, but community cases occur.

Detection: Labs screen for reduced susceptibility to third-generation cephalosporins and confirm with tests that demonstrate inhibition by clavulanic acid (e.g., combination disk tests, Etest with clavulanate) per CLSI/EUCAST guidelines. Distinguishing ESBLs from AmpC producers and other resistance mechanisms is important for therapy.

Treatment: Empiric therapy should be guided by local resistance patterns; carbapenems have been the standard treatment for severe infections caused by ESBL producers. Depending on susceptibility, options may include beta-lactam/beta-lactamase inhibitor combinations or newer agents such as ceftazidime-avibactam or other beta-lactamase inhibitors. De-escalation to targeted therapy when results are available is recommended.

Infection control: Containment relies on standard and contact precautions, hand hygiene, environmental cleaning, and antimicrobial stewardship to limit spread of ESBL-producing organisms, which can disseminate via plasmids among bacterial populations.