title: Antimicrobial resistance, virulence factors and genetic diversity of Escherichia coli isolates from household water supply in Dhaka, Bangladesh.
abstract: BACKGROUND
  Unsafe water supplies continue to raise public health concerns, especially in urban areas in low resource countries. To understand the extent of public health risk attributed to supply water in Dhaka city, Bangladesh, Escherichia coli isolated from tap water samples collected from different locations of the city were characterized for their antibiotic resistance, pathogenic properties and genetic diversity.
  
  
  RESULTS
  A total of 233 E. coli isolates obtained from 175 tap water samples were analysed for susceptibility to 16 different antibiotics and for the presence of genes associated with virulence and antibiotic resistance. Nearly 36% (n = 84) of the isolates were multi-drug(≥ 3 classes of antibiotics) resistant (MDR) and 26% (n = 22) of these were positive for extended spectrum β-lactamase (ESBL). Of the 22 ESBL-producers, 20 were positive for bla CTX-M-15, 7 for bla OXA-1-group (all had bla OXA-47) and 2 for bla CMY-2. Quinolone resistance genes, qnrS and qnrB were detected in 6 and 2 isolates, respectively. Around 7% (n = 16) of the isolates carried virulence gene(s) characteristic of pathogenic E. coli; 11 of these contained lt and/or st and thus belonged to enterotoxigenic E. coli and 5 contained bfp and eae and thus belonged to enteropathogenic E. coli. All MDR isolates carried multiple plasmids (2 to 8) of varying sizes ranging from 1.2 to >120 MDa. Ampicillin and ceftriaxone resistance were co-transferred in conjugative plasmids of 70 to 100 MDa in size, while ampicillin, trimethoprim-sulfamethoxazole and tetracycline resistance were co-transferred in conjugative plasmids of 50 to 90 MDa. Pulsed-field gel electrophoresis analysis revealed diverse genetic fingerprints of pathogenic isolates.
  
  
  CONCLUSIONS
  Multi-drug resistant E. coli are wide spread in public water supply in Dhaka city, Bangladesh. Transmission of resistant bacteria and plasmids through supply water pose serious threats to public health in urban areas.
authors.affiliation: Food Safety Research Group, Centre for Food and Waterborne Diseases, International Centre for Diarrhoeal Disease Research, Bangladesh, Mohakhali, Dhaka, Bangladesh.
authors.forename: Prabhat Kumar
authors.initials: PK
authors.lastname: Talukdar
authors.forename: Mizanur
authors.initials: M
authors.lastname: Rahman
authors.forename: Mahdia
authors.initials: M
authors.lastname: Rahman
authors.forename: Ashikun
authors.initials: A
authors.lastname: Nabi
authors.forename: Zhahirul
authors.initials: Z
authors.lastname: Islam
authors.forename: M Mahfuzul
authors.initials: MM
authors.lastname: Hoque
authors.forename: Hubert P
authors.initials: HP
authors.lastname: Endtz
authors.forename: Mohammad Aminul
authors.initials: MA
authors.lastname: Islam
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics; D001459:Bangladesh; D060766:Drinking Water / Q000382:microbiology*; D018432:Drug Resistance, Multiple; D004926:Escherichia coli / Q000187:drug effects* / Q000235:genetics; D014644:Genetic Variation; D006801:Humans; D008826:Microbial Sensitivity Tests; D058889:Molecular Typing; D037521:Virulence Factors / Q000235:genetics*; D014871:Water Microbiology; D018440:beta-Lactam Resistance; D001618:beta-Lactamases / Q000235:genetics
chemical_list: D001426:Bacterial Proteins; D060766:Drinking Water; D037521:Virulence Factors; C473109:beta-lactamase CTX-M-15; D001618:beta-Lactamases