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.

Development of a Screening Method and Device for the Detection of Escherichia coli from Agri-Food Production Environments and Fresh Produce

“…Thus, several studies have validated the Colilert system on different matrices, such as raw meat, fresh-cut products, and marine and other types of water samples [8][9][10][11][12][13]. Our findings supported the results of Julian et al [28] that 98.9% of presumptive E. coli isolated from hands, soil, and fecal samples using the Colilert reagent was finally confirmed as E. coli. Kawasaki et al [11] reported that E. coli was detectable from vegetables using the DOX system with Colilert-18.…”

“…The accuracy of the Colilert system can be impacted by both the aforementioned microbiota within the matrix and the matrix itself. For example, the acidity in fruit juice impairs the fluorescence of 4-methylumbelliferone [28]. Thus, several studies have validated the Colilert system on different matrices, such as raw meat, fresh-cut products, and marine and other types of water samples [8][9][10][11][12][13].…”

Investigation of Phylogenic Relationship Among Escherichia Coli Isolated From Clinical and Subclinical Mastitis in Different Animals in Basrah Province

“…Additionally the results on (Tab.1) revealed the prevalence of E.coli isolation from milk samples from different infected animals based on culturing identification. where 88% isolates were identified as E. coli (27). A recently report revealed E.coli isolated from mastitic milk samples were identification by the API 20 E showed about 12.4% as E.coli (28).…”

High Genomic Diversity and Heterogenous Origins of Pathogenic and Antibiotic-Resistant Escherichia coli in Household Settings Represent a Challenge to Reducing Transmission in Low-Income Settings

“…The placement of soil E. coli in terminal lineages of the phylogeny with fecal E. coli suggests the fluidity and lack of phylogenetic structure based on source. Humans and animals are suggested as likely contributors to the E. coli population in soils (28,35), but clonality or an estimate of the time of diversification between E. coli in soil and E. coli from the input source has not yet been established. Mutation rates are routinely used to establish time of diversification (36,37).…”