CTXM2

CTXM2, also known as CTX-M-2, is a beta-lactamase enzyme belonging to the CTX-M family of extended-spectrum beta-lactamases (ESBLs). Like other CTX-M enzymes, CTXM2 hydrolyzes beta-lactam antibiotics, particularly cefotaxime, and can confer resistance to many third-generation cephalosporins in Gram-negative bacteria. It is one of many CTX-M variants identified in Enterobacterales and is frequently encoded on plasmids, facilitating horizontal transfer between species.

Discovery and distribution: CTX-M-2-type enzymes were described in clinical isolates in the early 2000s and have since been reported in multiple regions around the world. Their mobility is aided by association with mobile genetic elements such as insertion sequences and transposons, enabling rapid dissemination within hospitals and community settings.

Structure and mechanism: CTX-M enzymes are class A beta-lactamases that use a serine-based catalytic mechanism to hydrolyze the beta-lactam ring. CTXM2 variants differ from other CTX-M enzymes by a small set of amino acid substitutions, which can affect substrate range and inhibition profile. In general, CTX-M-2 exhibits strong activity against cefotaxime and variable activity against ceftazidime.

Clinical significance and detection: Expression of CTXM2 can produce an extended-spectrum beta-lactamase phenotype, reducing susceptibility to many penicillins and cephalosporins. Diagnosis relies on phenotypic ESBL screening and confirmatory tests, complemented by molecular detection of blaCTX-M-2. Treatment typically relies on carbapenems or other agents with reliable activity against ESBL producers, guided by susceptibility testing.