In-vitro activity of conventional and novel β-lactam combinations against multidrug-resistant Klebsiella pneumoniae

Abstract

Background: The rise of multidrug-resistant (MDR) Klebsiella pneumoniae poses a significant challenge in hospitals due to limited treatment choices and increasing antimicrobial resistance. This study aims to analyse the antimicrobial resistance patterns of MDR K. pneumoniae , identify the prevalence of extended-spectrum β -lactamase (ESBL) and carbapenemase producers, and evaluate the in vitro effectiveness of various β -lactam/ β -lactamase inhibitor combinations. Materials and Methods: A cross-sectional study was conducted from October 2025 to March 2026 at the Department of Microbiology, Maharishi Markandeshwar Institute of Medical Sciences and Research, Mullana, India. It included 165 MDR K. pneumoniae isolates from various clinical samples. Identification and antimicrobial susceptibility testing were performed using the VITEK-2 Compact system and the Kirby–Bauer disc diffusion method, according to CLSI/EUCAST guidelines. ESBL production was detected via the combination disc method, and carbapenemase production was identified using mCIM and eCIM tests. Results: Among the isolates, 53.2% were ESBL producers and 55.2% showed carbapenemase production. Serine β -lactamases were more common than metallo-β -lactamases. High resistance was observed against cephalosporins, aminoglycosides, and fluoroquinolones. Meropenem-vaborbactam and ceftazidime-avibactam demonstrated the best activity against serine β -lactamase-producing isolates, whereas none of the tested β -lactam combinations showed effective activity against metallo-β -lactamase producers. Conclusion: Newer β -lactam/ β -lactamase inhibitor combinations, especially ceftazidime-avibactam and meropenem-vaborbactam, have been effective against K. pneumoniae producing serine β -lactamases but demonstrated limited in vitro activity against metallo-β -lactamase producers.