Prevalence and patterns of antimicrobial resistance among Escherichia coli isolated from Zambian dairy cattle across different production systems

This study focused on the use of antibiotics on small and medium sized dairy farms as well as large commercial units in the central region of Zambia and its relationship to antibiotic resistance in Escherichia coli. A stratified random sample of 104 small, medium and commercial farms, representing approximately 20% of all dairy farms, was selected. On each farm, faecal samples were collected from a random sample of 3 animals per epidemiological unit on the farm (range 3-18 samples per farm) and a standardised questionnaire on the usage of antibiotics was completed. E. coli isolates were obtained from 98.67% (371/376) of the sampled animals and tested for resistance to six classes of antibiotics. The prevalence resistance levels across the different farming systems were: Tetracycline (Tet) (10.61;95%CI: 7.40-13.82), Ampicillin (Amp) (6.02;95%CI:3.31-8.73), Trimethoprim/Sulfamethaxazole (Sxt) (4.49; 95%CI:2.42-6.56), Cefpodoxime (Cpd) (1.91;95%CI:0.46-3.36), Gentamicin (Gen) (0.89;95%CI:-0.06-1.84) and Ciprofloxacin (Cip) (0% ; CI:0-0). Univariable analyses indicated certain diseases, exotic breeds, location, farm size and other management practices as risk factors whereas multivariable analyses showed a specific association with lumpy skin disease (LSD). This study has provided novel insights into the drivers of antibiotic use and their association with antibiotic resistance in an under-studied region of Southern Africa.