extendedspectrum

Extendedspectrum is a term used to describe a broadened range of activity or substrates for a drug, enzyme, or other biological molecule. In clinical microbiology, the phrase is most commonly associated with extended-spectrum beta-lactamases, enzymes produced by certain Gram-negative bacteria that can hydrolyze a wide range of beta-lactam antibiotics, including extended-spectrum cephalosporins such as cefotaxime, ceftriaxone, and ceftazidime, and sometimes monobactams like aztreonam.

ESBLs were first identified in the 1980s and have since diversified into several families, notably TEM, SHV, and CTX-M. Many ESBL genes are carried on plasmids, enabling rapid spread among Enterobacterales, including Escherichia coli and Klebsiella pneumoniae. The presence of ESBLs often correlates with multidrug resistance, complicating treatment choices.

Clinically, infections caused by ESBL-producing organisms are associated with higher morbidity and mortality and limited therapeutic options. Carbapenems are commonly used for serious ESBL infections, although rising resistance to carbapenems and other antibiotics has further constrained choices. Some non-carbapenem options, such as certain beta-lactam/beta-lactamase inhibitor combinations, may be effective for susceptible strains, but decisions rely on susceptibility testing and local resistance patterns. Infection control and antibiotic stewardship are essential to limit transmission and evolution of resistance.

Diagnosis involves phenotypic tests showing clavulanate-dependent synergy or improved activity with beta-lactamase inhibitors, alongside molecular methods to detect bla_TEM, bla_SHV, or bla_CTX-M genes. It is important to distinguish ESBL producers from AmpC producers and carbapenemase carriers, as this informs treatment and containment strategies.