Phenotypic detection of ESBL, AmpC, and MBL in Enterobacterales uropathogens: a two-center experience in Karachi, Pakistan

Abstract

Introduction: The emergence of extended-spectrum β-lactamases (ESBLs), AmpC β-lactamases, and carbapenemases; and their co-existence among Enterobacterales uropathogens present new diagnostic and therapeutic challenges. This study aimed to elucidate the phenotypic detection and co-occurrence of ESBL-, AmpC-, and carbapenemase-producing uropathogens.

Methodology: A cross-sectional study was conducted from 3 January to 26 July 2024, at the Department of Microbiology, Basic Medical Sciences Institute, in collaboration with the Department of Urology at Jinnah Postgraduate Medical Center and National Medical Centre, Karachi, Pakistan. A total of 260 non-repetitive urine samples were collected from hospitalized and community patients. Antimicrobial susceptibility was determined by disc diffusion; ESBL, AmpC, and carbapenemase producers were identified using the double disc synergy test (DDST), modified three-dimensional method, and lateral flow immunochromatographic (LFI) assay, respectively.

Results: Among the 260 cases, 207 (80%) showed positive growth, yielding 240 isolates. Out of 189 Enterobacterales, E. coli (131; 69.3%) was the most prevalent, followed by K. pneumoniae (46; 24.3%), P. mirabilis (3; 1.6%), E. cloacae (3; 1.6%), K. oxytoca (2; 1.1%), C. freundii (2; 1.1%), C. werkmanii (1; 0.5%), and P. rettgeri (1; 0.5%). There were 89 (47.1%) ESBL producers, 10 (5.2%) AmpC producers, and 59 (31.2%) carbapenem-resistant isolates. New Delhi metallo-beta-lactamase (NDM) was the dominant carbapenemase (33; 56%). Co-production of ESBL and NDM was the most common, and detected in 30 (19%) isolates.

Conclusions: The prevalence of ESBLs and carbapenemase producers was high, with frequent co-production of ESBL and NDM. Rapid, cost-effective phenotypic methods are crucial for timely detection and appropriate antimicrobial treatment.