Dairy cattle are common carriers of important foodborne pathogens. Escherichia coli, Salmonella and Campylobacter jejuni are among the commonest causes of foodborne diseases. The high prevalence of microbial infections is escalating antimicrobial usage in human health and for growth promotion and prophylaxis in animal health. Overuse of antimicrobials is increasing antimicrobial residues in animal source foods and accelerating antimicrobial resistance. The study collected 184 samples from 33 dairy farms and assessed the prevalence of Escherichia coli, Salmonella and Campylobacter jejuni and their AMR. Sample inoculation for bacterial isolation was by agar surface streaking method and broth dilution. Escherichia coli was isolated on Chromogenic Coliform agar at 37°C for 24 hour forming dark blue colonies confirmed by Indole, Methyl Red, Voges-Proskauer and Citrate biochemical tests. Escherichia coli antimicrobial susceptibility testing was done by a single disc diffusion method against eight standard antibiotics. Sensitive, Intermediate and Resistant system was used for reporting antimicrobial susceptibility testing results. Escherichia coli was isolated in 21.7% samples, Campylobacter jejuni and Salmonella were absent. Escherichia coli was isolated in fecal samples from 48.5% of study farms, 56.9% of fecal and 4.8% of water samples and not isolated in all milk samples tested. All Escherichia coli isolates were susceptible to gentamycin, ciprofloxacin, cefoxitin and cefotaxime but 9 were resistant to ampicillin, oxacillin, ceftazidime, and ceftriaxone, produced 4 penicillinase and 1 beta-lactamase while 4 didn’t exhibit any specific resistance mechanism. Aminoglycosides, quinolones, and furans showed no resistance. When stratified by sample, 7 fecal Escherichia coli isolates showed resistance compared to 2 water isolates. All fecal and water isolates were resistant to oxacillin. The majority of Beta-lactamase and penicillinase producing isolates were from fecal samples. Oxacillin was widely resisted hence it should not be used in routine treatment of bacterial infections to avoid treatment failures. All Escherichia coli isolates were susceptible to gentamycin, ciprofloxacin, cefoxitin and cefotaxime, 9 were resistant to ampicillin, oxacillin, ceftazidime, and ceftriaxone, produced 4 penicillinase and 1 beta-lactamase. Aminoglycosides, quinolones, and furans showed no resistance. There is a need to conduct continuous professional development training programmes for veterinarians and veterinary paraprofessionals to promote prudent use of antimicrobials. Access and use of gentamycin, ciproflaxacin, cefoxitin and cefotaxime by dairy farmers and unqualified people should be restricted to prevent or delay resistance to these four.
Antimicrobial susceptibility testing of escherichia coli isolated from selected dairy farms in and around mekelle, Ethiopia
