Thirty five litter samples of village chickens, 35 broilers and 32 samples of
raw milk were examined for the presence of E. coli. All samples were positive for
E. coli. Three hundred and five isolates of E. coli were isolated from litter samples
of village chickens (105 isolates), broilers (105 isolates) and raw milk samples (95
isolates). All the isolates were examined for antibiotic resistance, plasmid profiles
and polymorphism using random amplification of polymorphic DNA (RAPD)
analysis. Isolates isolated from litter of village chickens and broilers had a multiple
antibiotic resistance (MAR) index of 0.31 to 0.75 and 0.44 to 0.69, respectively.
Isolates isolated from raw milk had a MAR index of 0.31 to 0.88. High MAR
index suggests that all the isolates originated from high risk sources. The E. coli
isolates isolated from village chickens, broilers and raw milk samples were grouped into 34,30 and 28 distinct antibiotypes, respectively. Eighty (76.2%) and
99 (94.3%) isolates were found to harbour plasmids ranging in size from 1.2 to 64
MDa and 1.2 to 80 MDa among isolates isolated from village chickens and
broilers, respectively. Isolates isolated from raw milk harboured plasmids ranging
in size from 1.4 to 68 MDa. Based on their plasmid profiles, the E. coli isolates
isolated from village chickens, broilers and raw milk were grouped into 28, 57 and
5 plasmid patterns, respectively. Three l0-mer oligonucleotides primers (Gen1-50-02, Gen1-50-09 and Gen1-50-10) were used to amplify genomic DNA. The
profiles observed after electrophoretic separation for the three primers when
combined together were able to distinguish the E. coli isolates from village
chickens, broilers and raw milk into 92, 96 and 50 RAPD patterns, respectively.
The large number of subgroups within these isolates indicates that there is a high
degree of diversity within E. coli isolates, isolated from village chickens, broilers
and raw milk samples. Isolates, isolated from village chickens, broilers and raw
milk are genotypically diverse as shown by RAPD pattern, suggesting that
different strains have been brought into the geographic region and strains already
present have continued to evolve. These results suggest that RAPD-PCR assay is
more discriminating than plasmid profiling and antibiotyping, and could be a
valuable tool for epidemiological studies