ANTIMICROBIAL SUSCEPTIBILITY PATTERNS OF ESCHERICHIA COLI ISOLATED FROM PATIENTS IN CALCUTTA SCHOOL OF TROPICAL MEDICINE

Abstract

This study aimed to determine the prevalence and antimicrobial susceptibility patterns of Escherichia coli (E. coli) isolated from clinical samples, primarily urine, at the Calcutta School of Tropical Medicine. Increasing rates of antimicrobial resistance in E. coli, particularly the emergence of Extended Spectrum Beta-Lactamases (ESBLs), pose a growing worldwide concern in treating infections like Urinary Tract Infections (UTIs), which E. coli is the leading cause of. 

OBJECTIVE: The aim of this study is to determine the prevalence and antimicrobial susceptibility of E. coli from clinical samples.

Methodology

A retrospective review was conducted on results from urine cultures, and data on E. coli isolates and their antimicrobial susceptibility were collected. Isolates were identified using MacConkey agar culture (showing pink-red colonies), Gram staining, and a panel of biochemical tests (Citrate, Urease, SIM, and TSI). Antimicrobial susceptibility was evaluated using the Kirby-Bauer disk diffusion method on Mueller-Hinton agar. 

Results and Conclusion

Of the 487 urine samples analyzed between June and July 2022, 12.3% yielded E. coli isolates, with the highest isolation rate observed in urine specimens. The study found a significantly high overall resistance of E. coli to certain groups of antibiotics, with resistance rates for Ampicillin being the highest (>60%) and for Cephalosporins being high (around <50% >). Ampicillin is no longer recommended for the empirical treatment of UTIs due to this high resistance. High resistance was also observed for Co-trimoxazole (55%) and Ciprofloxacin (53.44%). 

Conversely, the isolates showed high susceptibility to certain antibiotics. Fosfomycin (resistance rate <5%) and Amikacin (resistance rate 5.17%) were found to be highly active. 

The emergence of resistance among uropathogenic E. coli to penicillin, cephalosporin, quinolone, fluoroquinolones, and sulfonamides limits their use as first-line UTI treatments. The study concludes that fosfomycin and nitrofurantoin could be considered appropriate antimicrobials for empirical therapy of UTIs due to their high susceptibility. Regular and continuous monitoring of antibiotic susceptibility is vital to guide and optimize empirical treatment.