Abstract
Aquatic environments, under frequent anthropogenic pressure, could serve as reservoirs that provide an ideal condition for the acquisition and dissemination of antibiotic resistance genetic determinants. We investigated the prevalence and diversity of antibiotic-resistant Escherichia coli by focusing on their genetic diversity, virulence, and resistance genes in anthropogenic-impacted Larut River. The abundance of E. coli ranged from (estimated count) Est 1 to 4.7 × 105 (colony-forming units per 100 ml) CFU 100 ml−1 to Est 1 to 4.1 × 105 CFU 100 ml−1 with phylogenetic group B1 (46.72%), and A (34.39%) being the most predominant. The prevalence of multiple antibiotic resistance phenotypes of E. coli, with the presence of tet and sul resistance genes, was higher in wastewater effluents than in the river waters. These findings suggested that E. coli could be an important carrier of the resistance genes in freshwater river environments. The phylogenetic composition of E. coli and resistance genes was associated with physicochemical properties and antibiotic residues. These findings indicated that the anthropogenic inputs exerted an effect on the E. coli phylogroup composition, diversification of multiple antibiotic resistance phenotypes, and the distribution of resistance genes in the Larut River.
Highlights
Escherichia coli (E. coli) of the family Enterobacteriaceae, is a Gram-negative, facultative anaerobe, non-spore-forming, rod-shaped, commensal, and potentially pathogenic bacterium that resides largely in the gastrointestinal tracts of warm-blooded vertebrate animals [1–3]
The results clearly showed that Larut River was affected by anthropogenic wastewaters that harbored more coliform and E. coli (1–5 log CFU 100 ml−1 difference) compared to river waters (p ≤ 0.05)
The coliform and E. coli concentrations detected in this study were within the range that is previously reported for polluted Malaysian rivers and other locations [18, 44–47], which exceeded the standard maximum 100 CFU 100 ml−1 limit in the National Water Quality Standards (NWQS) class II for rivers set by the Department of Environment (DOE) Malaysia and the Malaysia Interim Marine Water Quality Standards [25]
Summary
Escherichia coli (E. coli) of the family Enterobacteriaceae, is a Gram-negative, facultative anaerobe, non-spore-forming, rod-shaped, commensal, and potentially pathogenic bacterium that resides largely in the gastrointestinal tracts of warm-blooded vertebrate animals [1–3]. Most E. coli strains are harmless, and only some are pathogenic. The pathogenic E. coli can be classified as either intestinal pathogenic E. coli (IPEC) or extraintestinal pathogenic E. coli (ExPEC). The IPECs are major diarrhoeagenic pathogens that cause gastroenteritis with six intestinal pathotype subgroups: enterohemorrhagic E. coli (EHEC), enteropathogenic E. coli (EPEC), enteroaggregative E. coli (EAEC), enterotoxigenic E. coli (ETEC), enteroinvasive E. coli (EIEC), and diffusely adherent E. coli (DAEC). ExPEC consists of three human pathotype subgroups: neonatal-meningitis E. coli (NMEC), uropathogenic E. coli (UPEC), sepsis-associated pathogenic E. coli (SePEC), and the avian pathogenic E. coli (APEC) [4]
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