Emergence of β-Lactamase Mediated Resistance among Enterobacterales: A Phenotypic Study from a Tertiary Care Hospital

Background Members of the order Enterobacterales are among the most common causes of both community-acquired and healthcare associated infections. The increasing emergence of β-lactamase–mediated resistance, particularly extended-spectrum β-lactamases (ESBL), AmpC and carbapenemases, has significantly reduced the effectiveness of commonly used antibiotics and poses a major challenge for clinical management. Objective This study was conducted to determine the distribution of Enterobacterales isolated from clinical specimens as well as evaluate the frequency of ESBL, AmpC & carbapenemase production using phenotypic detection methods. Methods This study was carried out in the Department of Microbiology at Maharishi Markandeshwar Medical College and Hospital, Solan, India, from August 2024 to July 2025. A total of 486 Enterobacterales isolates obtained. Identification and AST were performed according to standard laboratory procedures and CLSI guidelines. Phenotypic methods were used to detect β-lactamase production, including the double-disk synergy test for ESBL detection, boronic acid inhibition test for AmpC detection, Modified Carba NP test for carbapenemase detection and imipenem-EDTA synergy test for metallo-β-lactamase (MBL) detection. Results Among the 486 isolates, E-coli (331) was the most frequently isolated organism, followed by Klebsiella species (87) and Citrobacter species (47). Urine was the most common clinical specimen from which isolates were obtained. Phenotypic analysis showed that 38% of isolates produced ESBL, 27% produced AmpC β-lactamase, and 17% demonstrated carbapenemase activity. Additionally, metallo-β-lactamase production was detected in 14% of isolates. A considerable proportion of isolates also exhibited multidrug resistance, particularly among Escherichia coli and Klebsiella species. Conclusion The study highlights a substantial prevalence of β-lactamase–mediated resistance among Enterobacterales in the studied healthcare setting. The presence of ESBL, AmpC, and carbapenemase-producing isolates emphasizes the need for routine laboratory detection, continuous surveillance, effective antimicrobial stewardship, and strict infection control measures to limit the spread of resistant pathogens.