Hydrochloric Acid Treatment for Rapid Recovery of Shiga Toxin-Producing Escherichia coli 026, 0111 and 0157 from Faeces, Food and Environmental Samples

Fukushima, Hiroshi; Gomyoda, Manabu

doi:10.1016/s0934-8840(99)80066-8

Cited by 20 publications

(28 citation statements)

References 16 publications

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“…The background microflora in food enrichments appeared to be more affected by a postenrichment acid treatment than E. coli O157 strains, thereby improving the selectivity of standard plating protocols for the recovery of this E. coli O157:H7 strain. The improved selectivity for EHEC strains, including O157:H7, from faeces and food by acidification (equal volume 1/8N HCl for 30 s) has been reported in other studies as well (Fukushima and Gomyoda 1999a,b). However, it is important to demonstrate that any acidification scheme employed (i) does not injure the target organism beyond recovery and (ii) strains representing various sources (patient, food, environmental) respond in a similar manner to commonly used reference strains.…”

Section: Discussionsupporting

confidence: 71%

“…2011). These attributes have been utilized in various pre‐enrichment isolation procedures to reduce background flora and improve recovery of pathogen (Fukushima and Gomyoda 1999b; Grant 2004, 2008). In previous studies, foods with high background flora such as alfalfa sprouts that had been artificially contaminated with E. coli O157:H7 ATCC 35150 have shown improved recovery of the pathogen using a postenrichment acidification (Fedio et al.…”

Section: Discussionmentioning

confidence: 99%

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Recovery of E. coli O157 strains after exposure to acidification at pH 2

Yoshitomi

Zapata

Jinneman

et al. 2012

Letters in Applied Microbiology

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Aims: Rapid detection and selective isolation of E. coli O157:H7 strains have been difficult owing to the potential interference from background microflora present in high background food matrices. To help selectively isolate E. coli O157H7 strains, a useful plating technique that involved acidifying the cultures to pH 2 was evaluated with a large number of E. coli O157:H7 strains to ensure response to treatment was consistent across strains. Methods and Results: Escherichia coli O157, 46 strains including ATCC 35150, were acidified to pH 2 following enrichment and plated onto Tryptic Soy Agar + 0·6% Yeast Extract (TSA‐YE) and Sorbitol MacConkey Agar + cefixime and tellurite (CT‐SMAC). Samples were enumerated and modest decreases in plate counts were observed on TSA‐YE media, with a greater reduction observed on CT‐SMAC. Conclusions: The acid‐resistant character of E. coli O157:H7 is a consistent trait and may be used for improved isolation of the organism from mixed cultures. Significance and Impact of the Study: There was little difference observed between the commonly used laboratory strain E. coli O157:H7 35150 and 45 other strains of E. coli O157 when subjected to acidifying conditions prior to plating, demonstrating that an acid rinse procedure was equally effective across a wide variety of E. coli O157 strains and broadly applicable for isolating unknown strains from food samples.

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Section: Discussionsupporting

confidence: 71%

Section: Discussionmentioning

confidence: 99%

Recovery of E. coli O157 strains after exposure to acidification at pH 2

Yoshitomi

Zapata

Jinneman

et al. 2012

Letters in Applied Microbiology

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“…The failure to identify these strains probably resulted from low numbers of these organisms in the respective stools, as indicated by colony blot hybridization, combined with the absence of a distinct sorbitol fermentation phenotype. CT-SMAC is a superior medium for the isolation of non-sorbitolfermenting EHEC O157:H7 (7,20); it was also successfully used to isolate EHEC O26 from acid-pretreated bovine feces (10). However, it does not distinguish sorbitol-fermenting E. coli O26 from other intestinal coliforms that are usually, but not always, reduced in density on CT-SMAC, because some of them also contain ter genes (26).…”

mentioning

confidence: 99%

Molecular Profiling and Phenotype Analysis of Escherichia coli O26:H11 and O26:NM: Secular and Geographic Consistency of Enterohemorrhagic and Enteropathogenic Isolates

et al. 2005

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Fifty-eight enterohemorrhagic Escherichia coli O26:H11 or O26:NM (nonmotile) strains and 44 atypical enteropathogenic E. coli O26:H11 or O26:NM strains isolated from patients in 11 countries during 52 years share a common pool of non-stx virulence genes, fitness loci, and genotypic and phenotypic diagnostic markers. These findings indicate close relatedness between these pathotypes and provide a basis for their clinical laboratory diagnosis.

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“…Acid exposure has been manipulated to improve recovery of generic and Shiga toxigeinc environmental E. coli (Gauthier et al, 1989; Fukushima and Gomyoda, 1999a), food, and animal manure (Grant et al, 2009; Fukushima and Gomyoda, 1999a; Fukushima and Gomyoda, 1999b). A second mechanism by which acid treatment may improve primary isolation of STEC is by inhibiting the non‐STEC background flora (Fukushima and Gomyoda, 1999a). Improved STEC enrichment has been reported in artificially inoculated laboratory experiments by exposing cells to a 1/8 mol L −1 hydrochloric acid treatment (Fukushima and Gomyoda, 1999a) and by pairing a prolonged exposure to pH 2 media with subsequent enrichment in a nonselective media (Grant, 2004).…”

Section: Shiga Toxigenic Escherichia Coli O157 Isolationmentioning

confidence: 99%

Primary Isolation of Shiga ToxigenicEscherichia colifrom Environmental Sources

Durso

2013

J. Environ. Qual.

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Since the time of the first microbe hunters, primary culture and isolation of bacteria has been a foundation of microbiology. Like other microbial methods, bacterial culture and isolation methodologies continue to develop. Although fundamental concepts like selection and enrichment are as relevant today as they were over 100 yr ago, advances in chemistry, molecular biology and bacterial ecology mean that today's culture and isolation techniques serve additional supporting roles. The primary isolation of Shiga toxigenic (STEC) from environmental sources relies on enriching the target while excluding extensive background flora. Due to the complexity of environmental substrates, no single method can be recommended; however, common themes are discussed. Brilliant Green Bile Broth, with or without antibiotics, is one of many broths used successfully for selective STEC enrichment. Stressed cells may require a pre-enrichment recovery step in a nonselective broth such as buffered peptone water. After enrichment, immunomagnetic separation with serotype specific beads drastically increases the chances for recovery of STEC from environmental or insect sources. Some evidence suggests that acid treating the recovered beads can further enhance isolation. Although it is common in human clinical, food safety, and water quality applications to plate the recovered beads on Sorbitol MacConkey Agar, other chromogenic media, such as modified CHROMagar, have proven helpful in field and outbreak applications, allowing the target to be distinguished from the numerous background flora. Optimum conditions for each sample and target must be determined empirically, highlighting the need for a better understanding of STEC ecology.

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Hydrochloric Acid Treatment for Rapid Recovery of Shiga Toxin-Producing Escherichia coli 026, 0111 and 0157 from Faeces, Food and Environmental Samples

Cited by 20 publications

References 16 publications

Recovery of E. coli O157 strains after exposure to acidification at pH 2

Recovery of E. coli O157 strains after exposure to acidification at pH 2

Molecular Profiling and Phenotype Analysis of Escherichia coli O26:H11 and O26:NM: Secular and Geographic Consistency of Enterohemorrhagic and Enteropathogenic Isolates

Primary Isolation of Shiga ToxigenicEscherichia colifrom Environmental Sources

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