Antibiotic Resistance and Extended-Spectrum Beta-Lactamase (ESBL) Production of Escherichia coli (E. coli) from Small Ruminants in Lesotho

Abstract

Antimicrobial resistance in bacteria from food-producing animals is an important concern for animal health, food safety, and public health. This study investigated antimicrobial resistance patterns, multidrug resistance, and phenotypic extended-spectrum beta-lactamase (ESBL) production in Escherichia coli (E. coli) isolated from small ruminants in four agro-ecological zones of Lesotho. A total of 162 faecal samples were collected from sheep and goats up to six months of age in the Lowlands, Foothills, Highlands, and Senqu River Valley between September and December 2022. Samples were processed using enrichment and selective media, Gram staining, biochemical tests, and confirmatory chromogenic E. coli media. A total of 127 E. coli isolates were identified and subjected to antimicrobial susceptibility testing using the Kirby–Bauer disk diffusion method against eight antimicrobials from six classes. Phenotypic extended-spectrum beta-lactamase production was assessed using the double-disc synergy test, and multidrug resistance was defined as resistance to three or more antimicrobial classes. Resistance was highest to gentamicin (78.7%) and tetracycline (61.4%), followed by cefotaxime (37.8%), amoxicillin/clavulanic acid (36.2%), amikacin (24.4%), chloramphenicol (16.5%), and ceftazidime (10.2%). All isolates were susceptible to gatifloxacin. Forty-six isolates (36.2%) were multidrug resistant, with resistance profiles commonly involving aminoglycosides, aminopenicillins, cephalosporins, and tetracycline. Phenotypic extended-spectrum beta-lactamase production was detected in 15 isolates (11.8%). Resistance patterns varied across agro-ecological zones, with the Lowlands showing the highest number of multidrug-resistant isolates. The findings indicate the presence of multidrug-resistant and extended-spectrum beta-lactamase-producing E. coli among small ruminants in Lesotho and support the need for improved antimicrobial stewardship, surveillance, and responsible antimicrobial use in livestock production systems.