Sensitivity of methods for the isolation of Escherichia coli O157 from naturally infected bovine faeces

Tutenel, Ann; Piérard, Denis; Vandekerchove, Dominique; Hoof, Jan Van; Zutter, Lieven De

doi:10.1016/s0378-1135(03)00121-4

Cited by 31 publications

(21 citation statements)

References 16 publications

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“…Theoretically, enrichment followed by IMS should be able to detect as little as a single organism present in the initial sample. In the laboratory, however, the type and number of background bacterial flora, the type of broth used, the temperature, and the incubation time impact the sensitivity of detection (10,16,18). The reliable detection limit of Ͼ100 CFU/g of feces which we report herein is comparable to the results that Omisakin et al reported from a much smaller number of naturally colonized cattle (11).…”

Section: Discussionsupporting

confidence: 78%

Sensitivity of Escherichia coli O157 Detection in Bovine Feces Assessed by Broth Enrichment followed by Immunomagnetic Separation and Direct Plating Methodologies

LeJeune

Hancock²,

Besser

2006

J Clin Microbiol

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In order to more precisely predict food safety risks, the fecal presence of food-borne pathogens among animals at slaughter must be correctly determined. Quantification of Escherichia coli O157 is also desirable. In two separate experiments, detection and enumeration of a nalidixic acid-resistant strain of E. coli O157 in bovine feces was assessed by culture on MacConkey agar supplemented with nalidixic acid (MACnal) and compared to overnight broth enrichment followed by immunomagnetic separation (IMS) and to direct plating of dilutions of bovine feces onto sorbitol MacConkey agar containing cefixime and tellurite (SMACct). The sensitivity of detection of E. coli O157 by both direct plating and IMS was highly dependent upon the initial concentration of the target organism in the sample. Sensitivity of detection by IMS was poor below 100 CFU/g but was better, and not affected by initial E. coli O157 numbers, above this concentration. Sensitivity of detection of E. coli O157 in bovine feces at low initial concentrations is very poor for both direct plating and IMS. Direct plating of dilutions of bovine feces on SMACct can be used to determine the magnitude of fecal E. coli excretion among cattle excreting greater than 100 CFU/g. Among positive samples identified by direct plating on SMACct, the direct counts of E. coli O157:H7 were highly correlated with the estimates obtained with the MACnal plates (r ‫؍‬ 0.88, P < 0.001). Because the majority of cattle excrete less than 10 2 CFU E. coli O157/g feces, most studies, including those using IMS methods, probably grossly underestimate the prevalence of E. coli O157 in cattle.Contamination of foods, water, and other environmental niches with bovine manure has emerged as an important public health concern, especially with regard to the epidemiology of Escherichia coli O157:H7 infections in both humans and animals. Since cattle harbor E. coli O157:H7 in their digestive tracts, albeit transiently, they have been considered the primary reservoir for this important food-borne pathogen. Extensive efforts to understand the epidemiology of E. coli O157:H7 in the bovine host have been made. Theoretical models and empirical data have demonstrated that control of the magnitude and prevalence of E. coli O157:H7 in live animals (preharvest) may have a great impact on reducing the rate of contamination of foods of bovine origin with this pathogen (4, 7). However, to date, limited data on the magnitude of fecal E. coli O157:H7 shedding among animals destined for slaughter are available. In order to quantify the risks associated with the slaughter of E. coli O157:H7-positive animals and the effectiveness of potential preharvest mitigation strategies, accurate estimates of the prevalence and the frequency distribution of E. coli O157:H7 concentrations in bovine feces are required.To increase the diagnostic sensitivity, enrichment of large volumes (10 g or more) of bovine feces, followed by immunomagnetic separation (IMS), has been widely used for epidemiological studies of E. coli O157...

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Section: Discussionsupporting

confidence: 78%

Sensitivity of Escherichia coli O157 Detection in Bovine Feces Assessed by Broth Enrichment followed by Immunomagnetic Separation and Direct Plating Methodologies

LeJeune

Hancock²,

Besser

2006

J Clin Microbiol

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“…It is associated with human illnesses ranging from uncomplicated watery diarrhea to hemorrhagic colitis and hemolytic-uremic syndrome, which may result in death (22,24,31). Cattle are an important source of E. coli O157 (15,25,39), and many surveys around the world have been conducted to estimate the prevalence of E. coli O157 shedding by cattle (20).Much research has gone into improving the sensitivity of laboratory methods for the detection of E. coli O157 and the introduction of immunomagnetic separation (IMS) and selective isolation media has greatly improved the sensitivity of E. coli O157 isolation from bovine feces (4,5,35). In contrast, the distribution of E. coli O157 in bovine feces and its impact on the accuracy of prevalence estimates reported in bovine fecal E. coli O157 shedding surveys has largely been ignored.…”

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confidence: 99%

“…Much research has gone into improving the sensitivity of laboratory methods for the detection of E. coli O157 and the introduction of immunomagnetic separation (IMS) and selective isolation media has greatly improved the sensitivity of E. coli O157 isolation from bovine feces (4,5,35). In contrast, the distribution of E. coli O157 in bovine feces and its impact on the accuracy of prevalence estimates reported in bovine fecal E. coli O157 shedding surveys has largely been ignored.…”

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confidence: 99%

Distribution of Escherichia coli O157 in Bovine Fecal Pats and Its Impact on Estimates of the Prevalence of Fecal Shedding

Pearce

Fenlon²,

Low³

et al. 2004

Appl Environ Microbiol

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The distribution of Escherichia coli O157 in bovine feces was examined by testing multiple samples from fecal pats and determining the density of E. coli O157 in immunomagnetic separation (IMS)-positive fecal samples. The density of E. coli O157 in bovine feces was highly variable, differing by as much as 76,800 CFU g ؊1 between samples from the same fecal pat. The density in most positive samples was <100 CFU g ؊1 , the limit of reliable detection by IMS. Testing only one 1-g sample of feces per pat with IMS may result in a sensitivity of detection as low as 20 to 50%. It is therefore probable that most surveys have greatly underestimated the prevalence of E. coli O157 shedding in cattle and the proportion of farms with shedding cattle. The sensitivity of the detection of E. coli O157 in bovine feces can be as much as doubled by testing two 1-g samples per pat rather than one 1-g sample.Shiga-toxigenic Escherichia coli O157 is a major public health concern. It is associated with human illnesses ranging from uncomplicated watery diarrhea to hemorrhagic colitis and hemolytic-uremic syndrome, which may result in death (22,24,31). Cattle are an important source of E. coli O157 (15,25,39), and many surveys around the world have been conducted to estimate the prevalence of E. coli O157 shedding by cattle (20).Much research has gone into improving the sensitivity of laboratory methods for the detection of E. coli O157 and the introduction of immunomagnetic separation (IMS) and selective isolation media has greatly improved the sensitivity of E. coli O157 isolation from bovine feces (4,5,35). In contrast, the distribution of E. coli O157 in bovine feces and its impact on the accuracy of prevalence estimates reported in bovine fecal E. coli O157 shedding surveys has largely been ignored. A variety of sampling techniques have been used to collect bovine feces in surveys, including rectal swabs (11,19), rectal grab samples (15, 39), and grab or swab samples from fecal pats (10,12). In 27 surveys we reviewed, only one sample was taken from each animal or fecal pat. In 9 of these surveys, a swab from each animal or fecal pat was tested (1, 2, 10-12, 19, 29, 30, 38); in 7 surveys, 1 g of feces from each animal or pat was tested (8,16,25,26,28,32,36); in 10 surveys, Ն10 g of feces from each animal or pat was tested (3, 7, 9, 13-15, 18, 23, 34, 39). In the remaining survey, the amount of feces tested was not reported (17). The analysis of results in these 27 studies implicitly assumed homogenous distribution of E. coli in the fecal samples tested.This study investigated the distribution of E. coli O157 in bovine feces and assessed its impact on the sensitivity of shedding survey results. MATERIALS AND METHODSSampling. Fecal samples were drawn from two separate studies. In both studies, convenience samples of fecal pats were taken, with pats being sampled without replacement. In the first study, multiple 10-to 25-g samples were taken from fecal pats in three separate pens of cattle housed on straw bedding. On 23 October 2001,...

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“…The O174 strain may have persisted on the farm even for years before the cleaning of the cowshed with a pressure cleaner exposed the farmer to the causative strain at concentrations high enough to lead to symptomatic infection. Specific PCR methods (1,4,6,7,10,15,23,25) and IMS (24,31) are powerful tools when certain characteristics, including virulence-associated genes and O antigens, etc., must be screened. However, IMS is currently available only for the most common STEC serogroups, O26, O103, O111, O145, and O157.…”

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confidence: 99%

Tracing Shigatoxigenic Escherichia coli O103, O145, and O174 Infections from Farm Residents to Cattle

Heinikainen

Pohjanvirta

Eklund³

et al. 2007

J Clin Microbiol

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Sensitivity of methods for the isolation of Escherichia coli O157 from naturally infected bovine faeces

Cited by 31 publications

References 16 publications

Sensitivity of Escherichia coli O157 Detection in Bovine Feces Assessed by Broth Enrichment followed by Immunomagnetic Separation and Direct Plating Methodologies

Sensitivity of Escherichia coli O157 Detection in Bovine Feces Assessed by Broth Enrichment followed by Immunomagnetic Separation and Direct Plating Methodologies

Distribution of Escherichia coli O157 in Bovine Fecal Pats and Its Impact on Estimates of the Prevalence of Fecal Shedding

Tracing Shigatoxigenic Escherichia coli O103, O145, and O174 Infections from Farm Residents to Cattle

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