Asymptomatic healthy slaughterhouse workers in South Korea carrying Shiga toxin-producing<i>Escherichia coli</i>

Hong, Seonghun; Oh, Kyunghwan; Cho, Seung-Hak; Kim, Jong-Chul; Park, Mi-Sun; Lim, Hyun-Sul; Lee, Bok-Kwon

doi:10.1111/j.1574-695x.2009.00545.x

Cited by 23 publications

(16 citation statements)

References 39 publications

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“…Our findings are in line with previous studies reporting the spread of STEC in healthy individuals (28)(29)(30) and the occurrence of stx genes in stool samples in the general population (31). In two of those studies (29,31), stx-positive results were obtained in a first screening by PCR.…”

Section: Discussionsupporting

confidence: 82%

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Shiga Toxin 2-Encoding Bacteriophages in Human Fecal Samples from Healthy Individuals

Martínez-Castillo

Quirós

Navarro

et al. 2013

Appl Environ Microbiol

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b Shiga toxin-converting bacteriophages (Stx phages) carry the stx gene and convert nonpathogenic bacterial strains into Shiga toxin-producing bacteria. Previous studies have shown that high densities of free and infectious Stx phages are found in environments polluted with feces and also in food samples. Taken together, these two findings suggest that Stx phages could be excreted through feces, but this has not been tested to date. In this study, we purified Stx phages from 100 fecal samples from 100 healthy individuals showing no enteric symptoms. The phages retrieved from each sample were then quantified by quantitative PCR (qPCR). In total, 62% of the samples carried Stx phages, with an average value of 2.6 ؋ 10 4 Stx phages/g. This result confirms the excretion of free Stx phages by healthy humans. Moreover, the Stx phages from feces were able to propagate in enrichment cultures of stx-negative Escherichia coli (strains C600 and O157:H7) and in Shigella sonnei, indicating that at least a fraction of the Stx phages present were infective. Plaque blot hybridization revealed lysis by Stx phages from feces. Our results confirm the presence of infectious free Stx phages in feces from healthy persons, possibly explaining the environmental prevalence observed in previous studies. It cannot be ruled out, therefore, that some positive stx results obtained during the molecular diagnosis of Shiga toxin-producing Escherichia coli (STEC)-related diseases using stool samples are due to the presence of Stx phages.

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Section: Discussionsupporting

confidence: 82%

“…In two of those studies (29,31), stx-positive results were obtained in a first screening by PCR. Considering the methods described in those reports, it cannot be excluded that those authors detected Stx phages in addition to the STEC strains isolated.…”

Section: Discussionmentioning

confidence: 99%

Shiga Toxin 2-Encoding Bacteriophages in Human Fecal Samples from Healthy Individuals

Martínez-Castillo

Quirós

Navarro

et al. 2013

Appl Environ Microbiol

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“…It has been reported that humans can act as healthy asymptomatic carriers of non-O157 STEC (30). In addition to humans, rabbits also harbored STEC carrying both stx 1 and stx 2 genes.…”

Section: Discussionmentioning

confidence: 99%

Prevalence of Diarrhea-Associated Virulence Genes and Genetic Diversity in Escherichia coli Isolates from Fecal Material of Various Animal Hosts

Chandran

Mazumder

2013

Appl Environ Microbiol

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In order to assess the health risk associated with a given source of fecal contamination using bacterial source tracking (BST), it is important to know the occurrence of potential pathogens as a function of host. Escherichia coli isolates (n ‫؍‬ 593) from the feces of diverse animals were screened for various virulence genes: stx 1 and stx 2 (Shiga toxin-producing E. Eleven hosts were positive for only the eae (10.11%) gene, representing atypical EPEC, while two hosts were positive for both eae and EAF (1.3%), representing typical EPEC. stx 1 , stx 2 , or both stx 1 and stx 2 were present in 1 (0.1%,) 10 (5.56%), and 2 (1.51%) hosts, respectively, and confirmed as non-O157 by using a E. coli O157 rfb (rfb O157 ) TaqMan assay. STh and STp were carried by 2 hosts (2.33%) and 1 host (0.33%), respectively, while none of the hosts were positive for LT and ipaH. The repetitive element palindromic PCR (rep-PCR) fingerprint analysis identified 221 unique fingerprints with a Shannon diversity index of 2.67. Multivariate analysis of variance revealed that majority of the isolates clustered according to the year of sampling. The higher prevalence of atypical EPEC and non-O157 STEC observed in different animal hosts indicates that they can be a reservoir of these pathogens with the potential to contaminate surface water and impact human health. Therefore, we suggest that E. coli from these sources must be included while constructing known source fingerprint libraries for tracking purposes. However, the observed genetic diversity and temporal variation need to be considered since these factors can influence the accuracy of BST results.

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“…National studies in Korea showed that enterohemorrhagic E. coli (EHEC) is present in workers in the farm industry as well as slaughter houses, especially among people who have more opportunities to come into contact with cattle [14,15]. Therefore, not only carcasses during slaughter but also cattle on farms during the pre-slaughter stage should be treated to prevent the spread of STEC.…”

Section: Introductionmentioning

confidence: 99%

Prevalence and characteristics of Shiga toxin-producingEscherichia coli(STEC) from cattle in Korea between 2010 and 2011

et al. 2014

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A total of 156 Shiga-like toxin producing Escherichia coli (STEC) were isolated from fecal samples of Korean native (100/568, 18%) and Holstein dairy cattle (56/524, 11%) in Korea between September 2010 and July 2011. Fifty-two STEC isolates (33%) harbored both of shiga toxin1 (stx1) and shiga toxin2 (stx2) genes encoding enterohemolysin (EhxA) and autoagglutinating adhesion (Saa) were detected by PCR in 83 (53%) and 65 (42%) isolates, respectively. By serotyping, six STEC from native cattle and four STEC from dairy cattle were identified as O-serotypes (O26, O111, O104, and O157) that can cause human disease. Multilocus sequence typing and pulsed-field gel electrophoresis patterns highlighted the genetic diversity of the STEC strains and difference between strains collected during different years. Antimicrobial susceptibility tests showed that the multidrug resistance rate increased from 12% in 2010 to 42% in 2011. Differences between isolates collected in 2010 and 2011 may have resulted from seasonal variations or large-scale slaughtering in Korea performed to control a foot and mouth disease outbreak that occurred in early 2011. However, continuous epidemiologic studies will be needed to understand mechanisms. More public health efforts are required to minimize STEC infection transmitted via dairy products and the prevalence of these bacteria in dairy cattle.

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Asymptomatic healthy slaughterhouse workers in South Korea carrying Shiga toxin-producingEscherichia coli

Cited by 23 publications

References 39 publications

Shiga Toxin 2-Encoding Bacteriophages in Human Fecal Samples from Healthy Individuals

Shiga Toxin 2-Encoding Bacteriophages in Human Fecal Samples from Healthy Individuals

Prevalence of Diarrhea-Associated Virulence Genes and Genetic Diversity in Escherichia coli Isolates from Fecal Material of Various Animal Hosts

Prevalence and characteristics of Shiga toxin-producingEscherichia coli(STEC) from cattle in Korea between 2010 and 2011

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