Assessing antibiotic resistance profiles in Escherichia coli and Salmonella species from groundwater in the Mafikeng area, South Africa

Abstract

Escherichia coli and Salmonella species occur as normal flora in the gastrointestinal tract of animals and humans. However, pathogenic strains exist that cause disease in humans. Infections may result from the consumption of water and food contaminated with faeces of human and animal origin. In South Africa, residents of most rural communities rely on untreated ground water for survival. This practice results to the transfer of pathogenic micro-organism to humans and thus amplifies the need to identify contaminated water systems. Results obtained may adequately address water quality problems and hence protect public health. The study was conducted to isolate and determine the antibiotic resistance profiles of E. coli and Salmonella species from the groundwater obtained from two rural communities in the North-West province, S.A. Nineteen ground water samples were analyzed for characters of E. coli and Salmonella species. Only those isolates that satisfied all the primary (oxidase and the triple sugar iron) and secondary identification criteria (API 20E and rapid slide agglutination test) for E. coli and Salmonella species were used. A total of 63 E. coli and 64 Salmonella isolates were identified. The antibiotic susceptibilities of these isolates were evaluated against a panel of 10 antibiotics. A large proportion (56.7 to 57.6%) of the E. coli isolated from both Dibate and Verdwall were resistant to vancomycin. Similarly, large proportions (51.5 to 78.8%) of the E. coli isolated from Verdwall were resistant to ampicilin and erythromycin when compared to those isolated from Dibate. Furthermore, a higher percentage (90.0 to 100%) of Salmonellaisolated from both Dibate and Verdwall were resistant to ampicillin, erythromycin and vancomycin. AP-E-VA was the predominant phenotype for E. coli isolated from both Dibate and Verdwall in 40 and 20%, respectively, while the phenotypes AP-E-T-VA and AP-E-VA were dominant among the Salmonella species isolated in this study. The results indicated that E. coli and Salmonella could serve as indicator organisms necessary to assess the quality of ground water and their levels are critical parameters that could help to drive management strategies. This will limit the effect of these pathogens on consumers, as some water samples were visibly identified to be contaminated. Key words: Salmonella, E. coli, multiple antibiotic resistant (MAR), phenotype.