Antibiotic Resistance and Plasmid Profile of Pathogenic Bacteria Isolated From Drinking Water in Oshimili South L.G.A. of Delta State, Nigeria

A total of 20 drinking water sources comprising; well-water, river water, borehole water, sachet water and bottled
water were sampled from three towns (Asaba, Oko and Okwe) within Oshimili South Local Government Area of
Delta State, Nigeria. The total viable bacterial and coliform counts determined by spread plate technique ranged
from 1.6 x102 to 9.4 x104cfu/ml and 1.2 x 102 to 9.1 x 104 cfu/ml respectively. Identification of isolates done using
standard methods revealed the following; Escherichia species 57(10.9%), Bacillus species 56(10.8%), Salmonella
species 55(10.6%),Staphylococcusspecies 51(9.8%), Pseudomonasspecies 50(9.6%), Shigella species 47(9.0%),
Enterobacterspecies 40(7.7%), Proteusspecies 35(6.7%), Klebsiellaspecies 32(6.2%), Corynebacteriumspecies
30(5.7%), Enterococcusspecies 27(5.2%), Aeromonasspecies 25(46.8%) and Micrococcusspecies 13(2.5%).
Antibiotic sensitivity showed that the isolates were most susceptible to ciprofloxacin and Ofloxacin. About 86.27%
of all the gram negative isolates were resistant to Amoxicillin and 82.35% were resistant to Streptomycin while
90.9% of all gram positive bacteria isolates were resistant to Tetracycline. The plasmid analysis carried out
unraveled that the isolates; Klebsiella spp., Escherichia spp., Bacillus spp.and Proteus spp. had two bands of DNA
with molecular weight ranging from 8,000bp to 10,000bp while Staphylococcus spp. had no visible band indicating
that its resistance gene was integrated into the chromosome. Not all the borehole waters are safe for consumption
and the well waters were of poorer bacteriological quality, indicating health risk to the inhabitants of the area. The
danger of indiscriminate use of antibiotics by individuals should also be emphasized.