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Combined use of an immunomagnetic separation method and immunoblotting for the enumeration and isolation of Escherichia coli O157 in wastewaters
Author(s) -
GarcíaAljaro C.,
Bonjoch X.,
Blanch A.R.
Publication year - 2005
Publication title -
journal of applied microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.889
H-Index - 156
eISSN - 1365-2672
pISSN - 1364-5072
DOI - 10.1111/j.1365-2672.2004.02497.x
Subject(s) - immunomagnetic separation , escherichia coli , enumeration , microbiology and biotechnology , biology , serotype , intimin , enterobacteriaceae , bacteria , enrichment culture , salmonella , gene , biochemistry , genetics , mathematics , combinatorics
Aims: The detection of Escherichia coli O157:H7 in environmental samples is a human concern. The high persistence of this serotype in the environment suggests that contaminated animal wastewater could act as a potential reservoir. Nevertheless, the high levels of background microflora and cell damage because of environmental stress hamper the isolation of this pathogen without using enrichment methods. This study develops a method for the detection of E. coli and investigates its prevalence in animal and human wastewaters. Methods and Results: Incubation of the sample for 1 h 30 min at 37°C in peptone water supplemented with vancomycin and cefsulodin, enhanced the recovery of bacteria whilst ensuring that no growth occurred. Subsequently, a combination of immunomagnetic separation, cefixime–tellurite–sorbitol MacConkey (CT‐SMAC) plating and immunoblotting with specific O157 antibodies allowed the detection, enumeration and isolation of E. coli O157 strains in human, swine and cattle wastewaters, which presented values of 0·2, 0·4, and 1·0 log 10 ml −1 units, respectively. Some of the isolates carried genes coding for Shiga toxins, intimin and enterohemolysin. Conclusions: Escherichia coli O157 is commonly present in animal and human wastewaters. The developed method reduced the high rate of false positives reported for other technical approaches. Significance and Impact of the study: The confirmation of serotype by specific immunomethods is necessary to prevent false‐positive detection and incorrect enumeration.