Antimicrobial susceptibility and resistance profiles of Escherichia coli and Klebsiella pneumoniae in dairy milk and the milking environment from dairy farms in Lusaka, Zambia

Escherichia coli and Klebsiella species are the most common Gram-negative bacteria (GNB) that cause clinical mastitis in cattle and pose a threat to human health, as consumption of contaminated raw milk may produce various pathogenic conditions.This was a cross-sectional study that aimed to isolate Escherichia coli and Klebsiella pneumoniae from milk and soil on dairy farms in which 90 milk and 90 soil samples were collected from 30 farms around Lusaka province.Samples were processed using conventional microbiology and molecular methods.E. coli and K. pneumoniae were confirmed using uidA and KP-27 primers, respectively.Kirby Bauer disc diffusion method was used to determine antimicrobial susceptibility.Out of 69 isolates identified, 62 were E. coli (51.6% milk; 48.4% soil), and seven were K. pneumoniae (85.7% milk; 14.3% soil).The highest resistance recorded for E. coli and K. pneumoniae was to ampicillin (84%) and ceftazidime (86%), respectively.Thirty-seven isolates were resistant to tetracycline, cephalosporins, and trimethoprim-sulphamethoxazole and were subjected to Polymerase Chain Reaction (PCR) to detect resistance genes, 33% tet (A), 27% blaCTX-M, 37.8% blaTEM-1, 21.6% blaTEM-2, and 80% dfrA7.Cephalosporin-resistant isolates were screened for Extended Spectrum Beta-Lactamases (ESBLs) genes, of which (1/3) were blaCTX-M, and (2/3) were blaTEM-1 genes.