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Open Forum Infect Dis. 2014 Aug 12;1(2):ofu061. doi: 10.1093/ofid/ofu061. eCollection 2014 Sep.

Phylogenetic Clades 6 and 8 of Enterohemorrhagic Escherichia coli O157:H7 With Particular stx Subtypes are More Frequently Found in Isolates From Hemolytic Uremic Syndrome Patients Than From Asymptomatic Carriers.

Author information

1
Department of Bacteriology I , National Institute of Infectious Diseases , Tokyo , Japan.
2
Department of Microbiology and Molecular Genetics , Michigan State University , East Lansing.
3
Division of Bacteriology , Osaka Prefectural Institute of Public Health , Japan.
4
Department of Bacteriology , Toyama Institute of Health , Japan.
5
Fukuoka Institute of Health and Environmental Sciences , Japan.
6
Nagasaki Prefectural Institute for Environmental Research and Public Health , Japan.
7
Oita Prefectural Institute of Health and Environment , Japan.
8
Fukuoka City Institute for Hygiene and the Environment , Japan.
9
Microorganism Section , Kitakyusyu City Institute of Environmental Sciences , Fukuoka , Japan.
10
Miyazaki Prefectural Institute for Public Health and Environment , Japan.
11
Kumamoto Prefectural Meat Inspection Office , Japan.
12
Okinawa Prefectural Institute of Health and Environment , Japan.
13
Kyoto Prefectural Institute of Public Health and Environment , Japan.
14
Yamaguchi Prefectural Institute of Public Health and Environment , Japan.
15
Department of Bacteriology I , National Institute of Infectious Diseases , Tokyo , Japan ; Division of Microbiology , National Institute of Health Sciences , Tokyo , Japan.
16
Department of Genomics and Bioenvironmental Science, Frontier Science Research Center , University of Miyazaki , Japan.
17
Infectious Disease Surveillance Center , National Institute of infectious Diseases , Tokyo , Japan.
18
Interdisciplinary Research Organization , University of Miyazaki , Japan.
19
National Agriculture and Food Research Organization , National Institute of Animal Health , Ibaraki , Japan.
20
Division of Microbiology , National Institute of Health Sciences , Tokyo , Japan.

Abstract

BACKGROUND:

Enterohemorrhagic Escherichia coli (EHEC) O157:H7 infection causes severe diseases such as bloody diarrhea and hemolytic uremic syndrome (HUS). Although EHEC O157:H7 strains have exhibited high genetic variability, their abilities to cause human diseases have not been fully examined.

METHODS:

Clade typing and stx subtyping of EHEC O157:H7 strains, which were isolated in Japan during 1999-2011 from 269 HUS patients and 387 asymptomatic carriers (ACs) and showed distinct pulsed-field gel electrophoresis patterns, were performed to determine relationships between specific lineages and clinical presentation.

RESULTS:

Clades 6 and 8 strains were more frequently found among the isolates from HUS cases than those from ACs (P = .00062 for clade 6, P < .0001 for clade 8). All clade 6 strains isolated from HUS patients harbored stx2a and/or stx2c, whereas all clade 8 strains harbored either stx2a or stx2a/stx2c. However, clade 7 strains were predominantly found among the AC isolates but less frequently found among the HUS isolates, suggesting a significant association between clade 7 and AC (P < .0001). Logistic regression analysis revealed that 0-9 year old age is a significant predictor of the association between clade 8 and HUS. We also found an intact norV gene, which encodes for a nitric oxide reductase that inhibits Shiga toxin activity under anaerobic condition, in all clades 1-3 isolates but not in clades 4-8 isolates.

CONCLUSIONS:

Early detection of EHEC O157:H7 strains that belonged to clades 6/8 and harbored specific stx subtypes may be important for defining the risk of disease progression in EHEC-infected 0- to 9-year-old children.

KEYWORDS:

EHEC; HUS; O157; clade; stx

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