Isolation and Antibiotic Susceptibility of Escherichia Coli and Salmonella Gallinarum Isolated from Rats in Commercial Poultry Farms with Recurrent Colibacillosis and Fowl Typhoid Cases in Zaria, Nigeria

Against the background of persistent outbreaks of Fowl typhoid and Colibacillosis in five commercial layer farms in Zaria, Nigeria, this study was conducted to screen rats for Escherichia coli and Salmonella gallinarum in the farms, and to evaluate the susceptibility of the bacterial organisms to ten commonly used antimicrobial drugs in Zaria. A total of 250 rectal swabs of rats comprising Norway rats (Rattus norvegicus) and Roof rats (Rattus rattus) caught with sticky traps in the farms were analyzed. Standard methods were used to isolate E. coli and S. gallinarum. Biochemical characterization of E. coli and S. gallinarum was also done according to standard method. Disc diffusion method was used to determine the susceptibility of the organisms to ten antimicrobial agents: amoxycillin, chloramphenicol, ciprofloxacin, enrofloxacin, erythromycin, gentamycin, neomycin, nitrofurantoin, sulphamexazole and tetracycline. Of the 250 rats screened, 112 (44.8%) were positive for S. gallinarum and E. coli. The result indicated occurrence rates of 26.8% for E. coli and 18.0% for S. gallinarum in the rats screened. The antibiogram revealed that 38 (56.7%) of the E. coli and 29 (64%) of the S. gallinarum isolated were resistant to all drugs tested except ciprofloxacin and enrofloxacin. Complete resistance to nitrofurantoin was observed in 11.9% of E. coli and 13.3% of S. gallinarum. The need to introduce and sustain rat control programme was recommended. Special emphasis also needs to be given for the rational use of drugs to avoid problems of resistence among bacterial pathogens of poultry.