Molecular Characterization of Antibiotic Resistant Bacteria from Soil within Rivers State University, Nigeria

Abstract

Antibiotic resistance has become a subject of global concern to health systems all over the world and the shedding of antibiotic resistant bacteria from humans and animals into the soil is a threat to public health. This research was carried out to molecularly characterize and assess antibiotic resistant bacteria from soil in Rivers State University. Bacteria from soil in four locations; waste dump site, fish farm, poultry farm and home soil were enumerated and identified using standard microbiological techniques such as serial dilution, plating and incubation, isolation, biochemical testing and molecular identification. Sensitivity testing on the bacterial isolates was done using Kirby-Bauer Disk diffusion method. These resistant isolates were also subjected to molecular testing to ascertain the presence of resistant genes. The results revealed mean total Heterotrophic Bacterial Counts (THBC) for 32 samples ranged from 1.05±0.72 x 107 to 3.63±2.58x 107 CFU/g in fish farm and waste dump samples respectively. Total Coliform Counts (TCC) ranged from 3.65±2.91 x105 to 6.92±4.41 x105 CFU/g in Fish farm and Waste dump samples while Total Staphylococcal count ranged from 3.80±1.71 x104 to 11.46±9.21 x104 CFU/g in Fish farm and Waste dump samples respectively. Total Pseudomonad Count (TPC) ranged from 0.09±0.09 x 103 to 2.47±1.67x 103 CFU/g in Home soil and Fish farm samples. There was a difference (p≤0.05) in total heterotrophic bacterial, Staphylococcal and Pseudomonad counts, but no difference (p≥0.05) in total coliform. Seventy-nine (79) bacterial isolates were identified in this study belonging to the following genera; Bacillus spp, Staphylococcus spp., Micrococcus spp, Pseudomonas spp, Serratia spp, Proteus spp, Klebsiella spp, Salmonella spp and Escherichia spp with Staphylococcus (58.83%) having the highest occurrence and Pseudomonas (11.11%) had the least occurrence from the samples. Antibiotic sensitivity revealed that most isolates were resistant to many antibiotics tested with the highest resistance observed for Cefuroxime, Ceftazidime and Cefixime (100%) for the gram negative organisms and also Cefuroxime, Ceftazidime and Cloxacillin for gram positive bacteria. However, all bacteria showed sensitivity to gentamicin. Multiple Antibiotic resistance (MAR) index for all bacteria were above 0.2. Resistant bacterial isolates were identified molecularly as S. aureus, S. sciuri, M. luteus, B. cereus, B. subtilis, P. aeruginosa, S. mercescens, P. vulgaris, E. coli and Salmonella typhimurium. Pseudomonas aeruginosa, Serratia mercescens, Proteus vulgaris and E. coli had CTX-M gene present in their genome while Staphylococcus aureus, Staphylococcus sciuri, Micrococcus luteus, Bacillus cereus and Bacillus subtilis had the mecA gene present in their genome. This study has highlighted the rise in antibiotic resistance in bacteria from soil, hence, there is need to checkmate indiscriminate use of antibiotics in agriculture.