CTX-M group 9 extended-spectrum β-lactamases (ESBL) (e.g. CTX-M-9, CTX-M-14) are globally distributed and have been reported in the U.S., though less frequently than group 1. These enzymes also hydrolyze cefotaxime and related cephalosporins. Detecting bla_CTX-M-group-9 similarly indicates ESBL production; such isolates typically carry resistance to third-generation cephalosporins. Clinically, this mandates selection of carbapenem or other effective agents (as for any ESBL) and reinforces infection control measures to limit spread (Bush & Bradford 2020, Tzouvelekis et al. 2012)
Bush, K., & Bradford, P. A. (2020). Epidemiology of β-Lactamase-Producing Pathogens. Clinical microbiology reviews, 33(2), e00047-19. https://doi.org/10.1128/CMR.00047-19
Tzouvelekis, L. S., Markogiannakis, A., Psichogiou, M., Tassios, P. T., & Daikos, G. L. (2012). Carbapenemases in Klebsiella pneumoniae and other Enterobacteriaceae: an evolving crisis of global dimensions. Clinical Microbiology Reviews, 25(4), 682–707.
