Association of Plasmid Bearing Multi Drug Resistant Bacteria with High Mortalities in Nigerian Poultry

Bacteriological investigations were carried out on reported cases of low and high mortalities in commercial poultry in the year 2007-2009 in commercial flocks of breeders, layers, broilers, chicks and growers. Pure bacterial isolates obtained from dead birds, mainly Gram negative,  were tested for their biochemical and antibiotic susceptibility profiles using Microscan® Dried Gram-negative Breakpoint Combo Pannels. The microscan panel analysis bacterial isolates for 24 biochemical tests and up to 25 antimicrobial agents following 16-20 hours of incubation at 35-37oC. Bacteria isolated were Escherichia coli, Salmonella Enteritidis, Salmonella Pullorum, Salmonella Gallinarum, Citrobacter youngae, Klebsiella ozaneae, Klebsiella variicola, Enterobacter cloaceae, Hafnia alvei, Pasteurella gallinarum and Pasteurella multocida. The bacterial isolates showed resistance to 6-23 of the 25 antibiotics tested. Tetracycline and ampicilllin were found as the least potent drugs, with 90 and 90.91% resistance respectively. Resistance was obtained against antibacterial agents that are not in use in Nigerian poultry industry, such as the cephalosporins, carbapenems, piperacillin, tircacillin, amikacin, tobramcycin and levofloxacin suggesting possible genetic contribution to resistance. Thirty-four (85%) of the 40 pathogenic bacteria isolates treated for plasmid profile were found to be carrying plasmids. Plasmid DNA size 11.50 kbp was commonly observed (about 65%) among all the plasmid borne mdr bacteria, plasmid DNA size 10kbp (incidence of about 22% in plasmid borne bacteria) as well as a 26.3 kbp plasmid DNA and a 6.6 kbp plasmid DNA. The susceptibility of the plasmid bearing bacteria to antibiotics was enhanced following plasmid curing with sodium deodecyl sulphate.  Antibiotic susceptibility testing should guide treatment in all infections where organism can be cultured in veterinary medicine practice Keywords: Antibiotics, high mortalities, multi-drug resistant bacteria, plasmid, poultry