Antimicrobial Resistance Patterns of Extended-Spectrum Beta-Lactamase (ESBL) Producing Escherichia coli (E. coli) Isolated from Broiler Chickens in Maseru, Lesotho

Abstract

The indiscriminate use of antibiotics in poultry production has contributed significantly to the global rise in antimicrobial resistance (AMR). Extended-spectrum β-lactamase (ESBL)-producing Escherichia coli pose a major One Health concern because of their ability to resist multiple classes of antimicrobials and spread across human, animal, and environmental interfaces. Despite this, documented evidence on the extent of AMR in poultry in Lesotho remains limited. This study aimed to (i) determine the resistance patterns of ESBL-producing E. coli against selected antimicrobials and (ii) assess the prevalence of multidrug resistance (MDR) in broiler chickens in Maseru. A total of 87 E. coli isolates were recovered from cloacal samples collected from broiler chickens at grill farms in Maseru. MacConkey agar, Eosine Methylene Blue, and chromogenic medium were used for identification. Antimicrobial susceptibility was assessed using the Kirby-Bauer disc diffusion method, while ESBL production was confirmed using the double-disk synergy test. The antimicrobials examined were tetracycline, gatifloxacin, cefotaxime, amikacin, gentamicin, amoxicillin-clavulanic acid, chloramphenicol, and ceftazidime. ESBL production was confirmed in 98.9% of the isolates. Resistance was highest to tetracycline (100%), followed by gentamicin (87.36%), gatifloxacin (78.62%), amoxicillin-clavulanic acid (34.02%), chloramphenicol (20.69%), cefotaxime (19.70%), and ceftazidime (13.79%). All isolates were susceptible to amikacin. More than half of the isolates were resistant to three or more classes of antibiotics, with an MDR incidence of 57%. This study identified a high prevalence of ESBL-producing E. coli and MDR among broiler chickens in Maseru. The marked contrast between complete susceptibility to amikacin and complete resistance to tetracycline highlights the potential consequences of indiscriminate antibiotic use. These findings support the need for antimicrobial stewardship, continued professional training for health and agricultural professionals, and a One Health approach to reduce AMR risks across human, animal, and environmental health.