Antimicrobial resistance patterns of Escherichia coli isolated from raw cow milk and, from clinical specimens in a tertiary institution, Uganda – A cross sectional study

Abstract Background The drastic rise of antimicrobial resistance to alarming states is one of the major concerns of global health today. The overuse of antibiotics in animal husbandry has tremendously contributed to increased emergence of antimicrobial resistant bacteria. These resistant strains from animals can be transferred to humans through the food chain like raw milk which is a potential source of food-borne bacterial pathogens including E. coli . Objective The objective of this study was to compare the patterns of antibacterial resistance of the E. coli isolates of animal origin from raw milk samples and E. coli isolates obtained from clinical specimens in the Clinical Microbiology Laboratory of Makerere University. Methodology A cross-sectional study with purposive sampling was conducted between January and March 2024, on N= 124 raw cow milk samples obtained from diary shops in Kawempe division and 13 clinical samples obtained from the Clinical Microbiology Laboratory of Makerere University. Samples were initially enriched in nutrient broth, sub-cultured MacConkey agar and biochemical tests were used to identify samples with E. coli from which prevalencewas determined. The antibacterial resistance pattern of E. coli against the selected antibiotics was determined using the disk diffusion susceptibility method. Results Out of the 124 milk samples (77 from cans and 47 from packs), 40 (32.26%) milk samples had been contaminated with E. coli ; 39 (31.45%) from cans and 1 (0.81%) from packs. Resistance was observed in 5 antibiotics out of 11 (45.5%); with the highest resistance to ampicillin (32.5%) and cotrimoxazole (22.5%), followed by ceftriaxone (5%), cefotaxime (5%), and cefuroxime (5%). 2 (5%). E.coli isolates expressing extended spectrum beta lactamase (ESBL) were isolated one from pack and one from milk can. Highest resistance of E. coli from the clinical isolates was observed in cotrimoxazole (100%), ceftriaxone (83.3%), cefotaxime (80%), and cefuroxime (75%) followed by ciprofloxacin (69.2%), ampicillin (66.7%), ceftazidime (44.7%), chloramphenicol (27.3%), augmentin (20%), gentamycin (18.2%), and imipenem (14.3%). The percentage resistance was higher in clinical isolates than in milk isolates for all antibiotics tested. Despite the overall higher levels of resistance observed in clinical E. coli isolates compared to raw cow milk samples, there is an interesting relationship between the two sets of results. Specifically, the antibiotics that showed resistance in milk samples also reflected relatively high resistance levels in clinical isolates. Conclusion The relationship between antibiotic resistance patterns of E.coli from raw cow milk and clinical specimens highlights the need for a holistic One Health approach of antibiotic stewardship.