Molecular Characterization and Resistance Profiling of Multidrug-Resistance <i>Salmonella</i> Species Isolated from Southeast Nigerian River

Abstract

Water, which aids in the sustainability of life, also contributes to diseases, including Salmonella implicated diseases, attributable to human anthropogenic activities leading to cross-contamination and transfer of multi-drug-resistant pathogens. There is however need for  constant surveillance of public water. This study is aimed at molecular identification and resistance profiling of multidrugresistant  Salmonella spp. isolated from a Southeast, Nigerian River. Using water samples obtained from sites 1–8, the microbiological water quality  and faecal counts were determined using the membrane filtration technique. Salmonella spp. from the sample was isolated and  biochemically and molecularly characterized and the resistance profile to ciprofloxacin (5μg), chloramphenicol (30μg), amoxicillin (30μg),  and streptomycin (10μg) assessed using the Kirby-Bauer sensitivity technique. The mean faecal counts according to the sampling months  ranged from 35,000– 45,000CFU/100ml and according to the sites, ranged from 37233.3–41900CFU/ml. The preidentification of  the isolates was done using isolates with negative results to catalase, coagulase, Voges-Proskauer, urease, oxidase and gram-stain,  positive results to citrate, indole, methyl red, and alkaline/acid result to H₂S. The molecular identification confirmed seven Salmonella  enterica (coded M1 to M7)of different strains and subspecies. The strains showed the highest sensitivity to chloramphenicol (80%),  followed by ciprofloxacin (16%). The highest resistance was recorded with amoxicillin (98%), followed by streptomycin (48%). Detected  fluoroquinolone genes included QnrA, QnrSM, ParC, and gyrin some or all the isolates. The study revealed the presence of multi-drug  resistant S. enterica strains in the study site, further exposing the heavy contamination in the site and informing policymaking.