Multiple Drug-Resistant Escherichia coli Phylogroups from the Belmont Valley Integrated Algal Pond System

Escherichia coli isolates, commonly found as gut microflora in warm-blooded animals, are classified into the major phylogroups, A, B1, B2 and D, and further divided into subgroups: A0, A1, B1, B2(2), B2(3), D1 and D2. This study tracks and classifies E. coli strains along an integrated algal pond system (IAPS) during municipal sewage treatment. PCR-confirmed E. coli isolates were delineated into phylogroup by targeting genes chuA, yjaA and TSPE4.C2 using the triplex PCR assay. Antimicrobial susceptibility testing was by disk diffusion assay. A total of 120 E. coli isolates were confirmed by analysis of the uidA gene. Phylogenetic analysis revealed 57 isolates were group A with others in groups B2 (35), B1 (16) and D (12). Isolate susceptibility to antibiotics was norfloxacin > florfenicol > gatifloxacin > streptomycin > gentamicin. Nearly all isolates (117, 98%) were sulphamethoxazole- and penicillin G-resistant (115, 96%). Thus, resistance was manifest by all phylogroups and to 3-17 of drugs tested. These findings confirm presence of various multidrug-resistant E. coli phylogroups throughout the IAPS wastewater treatment process and emphasize the usefulness of multidrug resistance profiling as a tool for microbial source tracking and, with which to determine origin of faecal pollution.

Automated summary

This study identified multidrug-resistant Escherichia coli strains in various phylogroups during municipal sewage treatment, with most isolates showing resistance to multiple antibiotics. These findings highlight the usefulness of multidrug resistance profiling as a tool for microbial source tracking and determining the origin of fecal pollution.