Persistence of <i>bla</i>_CTX-M-15 Dominance in ESBL-Producing <i>Escherichia coli</i> and <i>Klebsiella pneumoniae</i> Strains: A Single-Center Study

Abstract

Context: Infections caused by extended-spectrum beta-lactamase (ESBL)-producing Escherichia coli and Klebsiella pneumoniae limit treatment options and increase reliance on last-line antibiotics. Although blaCTX-M-15 is the globally dominant ESBL genotype, recent data on its persistence in individual Malaysian hospitals are limited. Objectives: This study aimed to determine the prevalence and temporal persistence of blaCTX-M-15 among ESBL-producing E. coli (ESBLEC) and K. pneumoniae (ESBLKP) isolates from a tertiary care center over a 2-year period. Evidence Acquisition: ESBLEC and ESBLKP strains were collected from Hospital Canselor Tuanku Muhriz (HCTM) during two sampling periods: June 2022 to January 2023 and December 2023 to March 2024. Antimicrobial susceptibility testing was performed using VITEK 2, and results were retrieved through the WHONET system. ESBL genes were detected by PCR, and blaCTX-M-15 was subtyped among blaCTX-M-1-positive strains. Results: Blood and urine were the predominant sources of ESBL isolates in both sampling periods. blaCTX-M-1 was the most prevalent ESBL gene in both species. Among blaCTX-M-1-positive strains, blaCTX-M-15 persisted at high prevalence in ESBLEC (68.5% and 66.7% in the two sampling periods, respectively) and ESBLKP (92.9% in both sampling periods); however, temporal continuity across the unsampled interval remains unknown. The proportion of ESBLEC strains resistant to ceftazidime (CAZ) and cefepime (FEP) decreased during the 10-month interval from February to November 2023, whereas ESBLKP resistance profiles remained largely stable. Conclusions: blaCTX-M-15 remains dominant in HCTM, underscoring the need for continued molecular surveillance and antimicrobial stewardship.