Molecular Profiling of Antibiotic Resistant Bacteria and Genes in Raw and Drinking Water

Abstract

Antibiotic resistant bacteria and antibiotic resistant determinants are regarded as emerging public health threats in drinking water systems. Heterotrophic Plate Count bacteria in distribution pipes are used as direct parameters to assess the conditions of water in distribution systems. Moreover, the presence of pathogenic features in the organisms may also indicate the potential public health risks they may pose to consumers when present in the drinking water. The current study investigated the pathogenic potential of Heterotrophic Plate Count bacteria present in two drinking water distribution systems. A total of 40 samples were collected over four seasons from August 2016 to May 2017. Physiochemical analysis of the bulk water samples revealed that the pH levels were mostly alkaline and ranged between 7.37 and 9.62 for both the Mmabatho and Mafikeng Water Treatment Plants throughout the sampling period. Electric conductivity values for water from both plants exceeded the SANS 241 specified limits and ranged between 239 - 846 μs/cm per 100ml of bulk water sample. A total of 202 isolates were detected based on differences in pigmentation of colonies on chromogenic R2A medium. Isolates were screened against a panel of 11 antimicrobial agents using Kirby-Bauer agar disc diffusion method. A total of 68 multi-drug resistant isolates defined as those showing resistance to 3 or more antibiotics belonging to different classes were selected and further screened for pathogenic determinants such as Haemolysin, Proteinase, DNase, Oxidase and Lipase production. A large proportion 62% (42) of these isolates were ~ haemolytic, while only 27% (18) were a haemolytic. In addition, only a small proportion 19% (12) of the isolates produced the DNase enzyme. When screened for the presence of antibiotic resistant genes, by use of PCR assay a large proportion 39 (55.8%) of the isolates possessed the strA gene. On the contrary, the strB gene, aadA gene, dfrb1, dfrb2 gene, tetA gene and blacTX-M were detected in 30.8% (21), 16.2% (11), 19.1 % (13), 19.1 % (13), 4.4% (3), and 7.4% (5) of the isolates respectively. The identities of the isolates was determined by bacterial 16S rRNA sequencing and results revealed that isolates belonged to the families Enterobacteriaceae, Paenibacillaceae, Bacillaceae, Yersiniaceae, Xanthomonadaceae and Flavobacteriaceae that of which some members are of clinical importance. Data obtained in this study suggested that some members of the HPC isolates identified in the water bodies may pose severe public health complications to consumers as well as enormous therapeutic challenges to both the medical and veterinary professions.