Prevalence of extended spectrum beta lactamases and Metallo beta lactamases among Escherichia coli isolates in a tertiary care hospital, Thiruvananthapuram

Background: Antimicrobial resistance in Escherichia coli, particularly due to extended-spectrum β-lactamases (ESBL), Amp C β-lactamases, and Metallo-β-lactamases (MBL), poses a major therapeutic challenge. This study aimed to determine the prevalence of these resistance mechanisms among clinical E. coli isolates and to assess their antibiotic susceptibility patterns. Methods: A hospital-based cross-sectional study was conducted on 130 non-duplicate E. coli isolates obtained from urine, blood, sterile body fluids, and aspirates over six months in a tertiary care hospital in south India. Identification was performed using standard microbiological techniques. Antimicrobial susceptibility testing was carried out by Kirby-Bauer disc diffusion following CLSI guidelines. ESBL, Amp C, and MBL production was detected using phenotypic screening and confirmatory disc synergy tests. Results: ESBL production was detected in 67 (51.5%) isolates, MBL in 9 (7%), and AmpC in 6 (4.6%). Co-production of ESBL and MBL was observed in 2 (1.5%) isolates, while no isolate produced all three enzymes. The highest resistance was observed to ampicillin (96.1%), ceftriaxone (91.5%), and ciprofloxacin (77.6%). Colistin (100%) and tigecycline (98.4%) showed the highest susceptibility. ESBL-producing isolates were most susceptible to colistin (100%), tigecycline (97%), and carbapenems (68-73%), whereas MBL producers retained susceptibility mainly to colistin and tigecycline. Conclusions: The high prevalence of ESBL-producing E. coli and the emergence of MBL producers underscore the urgent need for continuous surveillance, rational antibiotic use, and strengthened antimicrobial stewardship programs to limit the spread of multidrug-resistant organisms.