A Comparative Study Of Antibiotic Resistance Profiles Among Enteric Bacteria In Broilers And Traditional Chicken From Selected Farms In Kericho, Kenya

ABSTRACT

Antibiotic resistance is a growing concern for public and animal health. Threats to public health could come from the transfer of pathogens from animals to people via indirect contact such as through food or by direct contact with animals during handling process. Development and prevalence of antibiotic resistance of Salmonella and Escherichia coli strains is common. There is also acquisition of pathogenicity by the commensals. The purpose of the present study was to determine the prevalence of the various intestinal bacteria, antibiotic susceptibility of Escherichia coli and Salmonella, possibility of transfer of genes responsible for resistance of isolates from broiler chicken. This was to evaluate the level of antibiotic resistance of the two bacteria strains named above in Kericho District. Isolates from indigenous chicken that scavenge were used as control population. Sampling was done in Ainamoi, Belgut, Soin and Kabianga divisions. Data collection was done from September 2008 up to February 2009. Rectal swabs were taken from 321 broilers and 364 indigenous (local) chicken that were randomly sampled. The inocula were cultured on various agars and incubated for 24- 48h at 37oC for identification. The pure isolates were subjected to susceptibility tests to twenty antibiotics using the disc diffusion technique. A proportion of 92.5% were resistant to one antibiotic, 65.31% to two, 45.40% to three, 32.75% to four, 25.48% to five, 09.64% to six and 02.57% to seven antibiotics. A total of 25 Escherichia coli isolates that were resistant to ampicillin and augmentin, and 17 resistant to nalidixic acid were subjected to in-vitro conjugation using E. coli J53 strain as the recipient. A total of 16 E. coli isolates underwent successful conjugation. Those that underwent successful conjugation were subjected to plasmid DNA profiling. Plasmids‟ molecular sizes were determined by coelectrophoresis with plasmids of known molecular size from E. coli strains R39 and V517 on 1% horizontal agarose gel. A total of 465 E. coli and 2 Salmonella isolates were analysed. The results showed no significant difference (F = 0.24, P = 0.633) in prevalence of resistance among isolates from indigenous chicken and broiler chicken at 95% confidence limit. The plasmids containing genes for antibiotic resistance were transferable through conjugation from one bacterium to another. Plasmids of varying molecular weight (147kb up to 3.0kb) were common in multiple drug resistance (MDR) E. coli. Prevalence of resistance decreased with increase in bird age in isolates from broiler chicken whereas the trend was opposite in those from indigenous chicken. Data was analysed using a computer package MINITAB 13.0. It is therefore important to monitor the susceptibility profiles of Escherichia coli to commonly available antibiotics since they could be a reservoir of genes carrying resistance.