Antimicrobial Resistance Profiles of Enterobacteriaceae in Surface Water From Streams and the Southern Gulf of Lake Tana, Ethiopia

Antimicrobial resistance (AMR) is a major global health concern, with resistant bacteria and genes spreading between humans, animals, and the environment. However, waterborne AMR in Enterobacteriaceae remains underexplored in developing countries such as Ethiopia. This study assessed the AMR profiles of Enterobacteriaceae isolated from 66 surface water samples collected from waste-receiving streams and the Gulf of Lake Tana. Bacteria were identified using standard microbiological methods, and antimicrobial susceptibility was tested by the Kirby–Bauer disk diffusion method. The most frequent isolates were Providencia alcalifaciens, Citrobacter spp., and Enterobacter spp. Resistance to first-generation cephalosporins ranged from 10.9% to 45.8% in stream isolates compared with 1.7% to 25.6% in lake isolates, while ceftriaxone resistance was detected in 13.5% and 4.5% of isolates, respectively. Among species, 30% of Escherichia coli, 22% of Enterobacter cloacae, and 12% of P. alcalifaciens were resistant to ceftriaxone, whereas resistance to cefazolin reached 40%, 67%, and 44%, respectively. Stream isolates also showed higher resistance to ampicillin (63%) and amoxicillin–clavulanic acid (29%) compared with lake isolates (50% and 12%). Overall, 44.8% of Enterobacteriaceae were multidrug-resistant. Significant differences in resistance were observed between stream and lake isolates for ciprofloxacin, ceftriaxone, trimethoprim–sulfamethoxazole, piperacillin–tazobactam, and cefazolin. The high prevalence of resistance to commonly used antibiotics, including third-generation cephalosporins, highlights the environmental dimension of AMR and underscores the urgent need for antimicrobial stewardship and surveillance in Ethiopia and similar settings.