title: Genotypic and phenotypic characterization of Escherichia coli isolates from feces, hands, and soils in rural Bangladesh via the Colilert Quanti-Tray System.
abstract: The increased awareness of the role of environmental matrices in enteric disease transmission has resulted in the need for rapid, field-based methods for fecal indicator bacteria and pathogen detection. Evidence of the specificity of β-glucuronidase-based assays for detection of Escherichia coli from environmental matrices relevant to enteric pathogen transmission in developing countries, such as hands, soils, and surfaces, is limited. In this study, we quantify the false-positive rate of a β-glucuronidase-based E. coli detection assay (Colilert) for two environmental reservoirs in Bangladeshi households (hands and soils) and three fecal composite sources (cattle, chicken, and humans). We investigate whether or not the isolation source of E. coli influences phenotypic and genotypic characteristics. Phenotypic characteristics include results of biochemical assays provided by the API-20E test; genotypic characteristics include the Clermont phylogroup and the presence of enteric and/or environmental indicator genes sfmH, rfaI, and fucK. Our findings demonstrate no statistically significant difference in the false-positive rate of Colilert for environmental compared to enteric samples. E. coli isolates from all source types are genetically diverse, representing six of the seven phylogroups, and there is no difference in relative frequency of phylogroups between enteric and environmental samples. We conclude that Colilert, and likely other β-glucuronidase-based assays, is appropriate for detection of E. coli on hands and in soils with low false-positive rates. Furthermore, E. coli isolated from hands and soils in Bangladeshi households are diverse and indistinguishable from cattle, chicken, and human fecal isolates, using traditional biochemical assays and phylogrouping.
authors.affiliation: Environmental Health Sciences and the Johns Hopkins Water Institute, Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland, USA tim.julian@eawag.ch.
authors.forename: Timothy R
authors.initials: TR
authors.lastname: Julian
authors.affiliation: Center for Food and Waterborne Diseases, icddr,b, Dhaka, Bangladesh.
authors.forename: M Aminul
authors.initials: MA
authors.lastname: Islam
authors.affiliation: Civil and Environmental Engineering, Stanford University, Stanford, California, USA Woods Institute for the Environment, Stanford University, Stanford, California, USA.
authors.forename: Amy J
authors.initials: AJ
authors.lastname: Pickering
authors.affiliation: Center for Food and Waterborne Diseases, icddr,b, Dhaka, Bangladesh.
authors.forename: Subarna
authors.initials: S
authors.lastname: Roy
authors.affiliation: Department of Geography and Environmental Engineering, Johns Hopkins University, Baltimore, Maryland, USA.
authors.forename: Erica R
authors.initials: ER
authors.lastname: Fuhrmeister
authors.affiliation: Division of Epidemiology, School of Public Health, University of California at Berkeley, Berkeley, California, USA.
authors.forename: Ayse
authors.initials: A
authors.lastname: Ercumen
authors.affiliation: Civil and Environmental Engineering, Stanford University, Stanford, California, USA.
authors.forename: Angela
authors.initials: A
authors.lastname: Harris
authors.affiliation: Environmental Health Sciences and the Johns Hopkins Water Institute, Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland, USA.
authors.forename: Jason
authors.initials: J
authors.lastname: Bishai
authors.affiliation: Environmental Health Sciences and the Johns Hopkins Water Institute, Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland, USA.
authors.forename: Kellogg J
authors.initials: KJ
authors.lastname: Schwab
mesh_terms: D015373:Bacterial Typing Techniques; D001459:Bangladesh; D004926:Escherichia coli / Q000145:classification* / Q000235:genetics / Q000302:isolation & purification* / Q000502:physiology; D005189:False Positive Reactions; D005243:Feces / Q000382:microbiology*; D060005:Genotyping Techniques; D005966:Glucuronidase / Q000032:analysis*; D006225:Hand / Q000382:microbiology*; D006801:Humans; D012424:Rural Population; D012988:Soil Microbiology
chemical_list: D005966:Glucuronidase