PP12-Comparison of antibiotic sensitivity in Escherichia coli isolated from natural water and ground water in Gampaha District

Abstract

Introduction

Antimicrobial resistance in water sources poses a risk to both human and animal health. Therefore, surveillance of water sources is essential.

Objective

Compare the antimicrobial sensitivity patterns of Escherichia coli in surface and groundwater sources of the Gampaha District.

Design, setting, and methods

Two water samples were collected by the author using a water collection tool from each of the 52 major surface water bodies (SWB) marked on Google Maps and the Department of Census, as well as 161 groundwater (GW) samples in the Gampaha District. All samples were processed according to the standard single-membrane-filtration method using nitrocellulose membranes. They were inoculated onto Membrane-Lactose-Glucuronide agar. E. coli colonies were further confirmed biochemically.

Antibiotic susceptibility tests were performed on E. coli isolates using the disc diffusion method (CLSI M100, vol. 34, 2024). In case of a similar ABST pattern from the same source, one isolate was used for analysis.

Results

There were 93 E.coli isolates selected from 104 SWB isolates and 84 E.coli from 161 GW samples. The contamination was 100% in SWBs and 52.17% in GW. The coliform counts were greater than 200 CFU/100 mL in 68.2% of SWB compared to 67.85% of GW.

Highest resistance rates of E. coli were noted for ampicillin in both types (54.8% in SWB, 45.2% GW). None of the isolates were resistant to ertapenem. Slightly higher resistance rates in SWBs compared to GW were noted for co-amoxiclav (19.4% vs. 17.9%), gentamicin (18.3% vs. 13.1%), and cefotaxime and ceftazidime (8.6% vs. 7.1%). A higher rate of resistance was noted for trimethoprim-sulfamethoxazole (9.7% vs. 14.3%) and tetracycline (15.1% vs. 17.9%). ESBL was detected in 5 isolates (5.37%) in SWB, and one isolates in GW. Amp-C beta-lactamases were detected with two isolates from GW. Multidrug resistance was observed in 19% of GW and SWB.

However, there was no statistically significant difference in the antibiotic susceptibilities between the isolates from the two sources.

Conclusion

Our findings reveal high rates of antibiotic resistance in NWBs and GW, which humans access for their daily needs. The implications of these findings highlight the critical need for urgent interventions against AMR in aquatic settings.