A total of 3564 E. coli isolates obtained from Yeongsan River basin of South Korea were investigated for their production of extended-spectrum β-lactamases (ESBLs) and potential pathogenicity to better understand the linkage between antibiotic-resistant pathogens in the environment and their public health risks. Interestingly, 60% (53 of 89) of the screen-positive ESBL producers were determined to be potentially one or both of the diarrheagenic and extraintestinal pathogenic (ExPEC) pathotypes, suggesting that trade-off between resistance and virulence of E. coli may not apply to this study. In addition, 67% (60 of 89) of the screen-positive ESBL producers possessed more than one β-lactamase gene, and most (59 of 63) of the ESBL producers had the CTX-M-14 enzyme, which is the most dominant ESBL and seems to be related to urban anthropogenic activities. About 68% (36 of 53) of the potential pathogenic strains were resistant to more than 2 non-β-lactam antibiotics. Results from this study indicate that the Yeongsan River basin has been contaminated with antibiotic-resistant and potential pathogenic E. coli strains. While few studies have examined pathogenecity of ESBL-producing bacteria, this study reports the possible public health risk which could be caused by the fecal indicator bacterium itself containing both ESBL genes and virulence factors. This will likely impact the dissemination of potential pathogenic E. coli producing ESBLs in the environment and suggests the need for further investigations of antibiotic-resistant pathogens to prevent public health impacts in the Yeongsan River basin.
Genotypic microbial source tracking (MST) methods are now routinely used to determine sources of fecal contamination impacting waterways. We previously reported the development of a pyrosequencing-based MST method that assigns contamination sources based on shared operational taxonomic units (OTUs) between fecal and environmental bacterial communities. Despite decreasing sequencing costs, pyrosequencing-based MST approaches are not used in routine water quality monitoring studies due in large part to difficulties in handling massive data sets and difficulties in determining sources of fecal contamination. In the studies presented here we describe the development of an online MST tool, PyroMiST ( http://env1.gist.ac.kr/∼aeml/MST.html) that uses total bacterial or Bacteroidetes 16S rDNA pyrosequencing reads to determine fecal contamination of waterways. The program cd-hit was used for OTU assignment and a Perl script was used to calculate the number of shared OTUs. The analyses require only a small number of pyrosequencing reads from environmental samples. Our results indicate that PyroMiST provides a user-friendly web interface for pyrosequence data that significantly reduces analysis time required to determine potential sources of fecal contamination in the environment.
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