Antimicrobial resistance of Escherichia coli from dairy cattle farms with different antimicrobial use practices in Ethiopia.

OBJECTIVE

This study investigated antimicrobial resistance (AMR) in commensal Escherichia coli from Ethiopian dairy farms and assessed associations with farm-level antimicrobial use (AMU).

METHODS

A cross-sectional study was conducted in six districts across intensive, semi-intensive, and extensive dairy systems. Eighty-three farms were selected using stratified sampling, and 1149 cattle and environmental samples (faeces, udder milk, bulk tank milk, and udder, bucket and floor swabs) were collected. E. coli was isolated using standard methods, and 310 isolates were tested for susceptibility to nine antimicrobials using the Bauer-Kirby disk diffusion method. Multidrug resistance (MDR) and multiple antibiotic resistance index (MARI) were calculated. Associations among AMU, production system, and location with AMR/MARI were assessed using mixed-effects regression models.

RESULTS

Oxytetracycline (80%) and penicillin-streptomycin (73%) were the most used antimicrobials. Penstrep use was significantly higher in central districts, whereas oxytetracycline use was lower in intensive systems. Resistance to more than one antimicrobial was detected in 89% of isolates, with high rates for tetracycline (65%), streptomycin (56%), and sulfisoxazole (43%). MDR was observed in 46.5% of the isolates. Intensive systems and sulphonamide use were statistically associated with higher odds of quinolone resistance, whereas oxytetracycline use was associated with aminoglycoside resistance. Farms in central Ethiopia had substantially higher odds of resistance to antifolates. MARI values were significantly higher in central districts and on farms using penicillin and sulphonamides.

CONCLUSIONS

AMR in E. coli is widespread in Ethiopian dairy farms, with AMU strongly associated with MDR. Targeted interventions are urgently needed to mitigate AMR and safeguard public health.