Occurrence of Tet Gene-Bearing Antimicrobial-Resistant Escherichia coli From Dairy Farms in Nigeria

Abstract

This study focused on antibiotic resistance genes as emerging contaminants with potential global human health implications. Intensive livestock farming has been identified as a major contributor to the spread of resistant bacteria and genes. The study examined antimicrobial-resistant Escherichia coli and tetracycline-resistant genes in raw milk from commercial dairy farms in Kano State. Out of 300 registered farms, 54 (18 %) were purposively sampled for the study. A total of 313 milk samples were collected and processed through enrichment and inoculation on selective media for Escherichia coli isolation. The antibiogram pattern of the isolated Escherichia coli strains was assessed using the disk diffusion method. The results revealed resistance to various antimicrobial agents, with no resistance to quinolones but high resistance to ampicillin (100 %), erythromycin (73.3 %), and tetracycline (46.7 %), among others. The multiplex polymer-ase chain reaction was conducted on all Escherichia coli isolates to detect tet genes (tet A, B, C, D, and M), and one isolate carried the tet M resistance gene, while six (40 %) others carried the tet A resistance gene. The study concludes that a significant proportion of the cultured Escherichia coli strains were resistant to one or more tested antibiotics, indicating a potential public health threat associated with Escherichia coli contamination in raw milk. We recommend implementing robust regulatory policies governing the use and sales of antimicrobials in animal production. Furthermore, we suggest further investigation into other resistant genes that these isolates might carry to better understand the extent of antibiotic resistance in the region.

Keywords

• antimicrobial resistance
• dairy cows
• escherichia coli
• raw milk