CTX-M-9 class A beta-lactamase (CTX-M-9)

CTX-M-9 class A beta-lactamase is a serine-based extended-spectrum beta-lactamase (ESBL) enzyme found primarily in Enterobacteriaceae, such as Escherichia coli and Klebsiella pneumoniae[1][2]. It hydrolyzes and inactivates a broad range of beta-lactam antibiotics, particularly third-generation cephalosporins like cefotaxime, due to the presence of a catalytic serine at its active site[1][6]. Classified under Ambler molecular class A and functional group 2be (Jacoby-Bush), CTX-M-9 and related enzymes are major contributors to antibiotic resistance in clinical infections[1][3]. The gene encoding CTX-M-9 (bla_CTX-M-9) can be plasmid-borne, facilitating horizontal gene transfer and rapid spread among diverse bacterial populations. CTX-M-9 enzymes are generally susceptible to inhibition by beta-lactamase inhibitors like clavulanic acid, though emerging variants may show resistance[1][2]. Their detection in clinical microbiology serves as both a marker of ESBL-mediated resistance and an epidemiological tool for tracking resistant bacteria[1][7]. The spread of CTX-M-9 poses significant clinical challenges, restricting the utility of commonly used beta-lactam antibiotics and contributing to increased healthcare burdens globally[1][2][3][6].

Other names

Cefotaximase-9CTX-M-9 enzymeCTX-M group 9 β-lactamaseExtended-spectrum β-lactamase CTX-M-9

Bacterial resistance: hydrolyzes the beta-lactam ring of antibiotics, rendering them ineffective Inhibition (by certain inhibitors such as clavulanic acid): inhibitor binds to enzyme’s active site, preventing its action on antibiotics