Yuheng Jiang¹, Pooja Rao¹, Huina Yang^1
1Department of Laboratory Medicine, Tan Tock Seng Hospital, Singapore

Antimicrobial-resistant infections pose a critical global health challenge. This study analyzed 21 months of data (January 2023–September 2024) from our hospital to examine the distribution and resistance patterns of carbapenemase-producing organisms (CPOs). Genotypes were identified using the XpertCARBA-R assay, detecting OXA-48, NDM-1, IMP, VIM, and KPC. Among 750 clinical isolates, 21% produced class B metallo-β-lactamases (MBLs) (predominantly NDM-1), which confer resistance to ceftazidime-avibactam (CZA) and ceftolozane-tazobactam (CT). The most prevalent carbapenemase was OXA-48 (57%), found primarily in Enterobacterales (n = 212). Antimicrobial susceptibility testing of OXA-48 producers (n = 61) revealed 100% susceptibility to CZA, but only 30% to CT. Among 378 isolates lacking carbapenemase genes, 35% were Pseudomonas aeruginosa. Susceptibility testing of a subset (n = 14) showed 35% susceptibility to CZA and 43% to CT. These results highlight the utility of CZA for OXA-48-producing Enterobacterales and the need for susceptibility-guided use of CZA and CT for non-MBL-producing multidrug resistant P. aeruginosa. This study underscores the importance of genotypic and phenotypic surveillance in tailoring antimicrobial therapies and combating resistance, emphasizing the need for localized resistance data for treatment optimization and to inform prevention efforts.