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.
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.
Department of Bacteriology I , National Institute of Infectious Diseases , Tokyo , Japan.
Sunao
S
Iyoda
Department of Microbiology and Molecular Genetics , Michigan State University , East Lansing.
Shannon D
SD
Manning
Division of Bacteriology , Osaka Prefectural Institute of Public Health , Japan.
Kazuko
K
Seto
Department of Bacteriology , Toyama Institute of Health , Japan.
Keiko
K
Kimata
Department of Bacteriology , Toyama Institute of Health , Japan.
Junko
J
Isobe
Fukuoka Institute of Health and Environmental Sciences , Japan.
Yoshiki
Y
Etoh
Fukuoka Institute of Health and Environmental Sciences , Japan.
Sachiko
S
Ichihara
Nagasaki Prefectural Institute for Environmental Research and Public Health , Japan.
Yuji
Y
Migita
Oita Prefectural Institute of Health and Environment , Japan.
Kikuyo
K
Ogata
Fukuoka City Institute for Hygiene and the Environment , Japan.
Mikiko
M
Honda
Microorganism Section , Kitakyusyu City Institute of Environmental Sciences , Fukuoka , Japan.
Tsutomu
T
Kubota
Miyazaki Prefectural Institute for Public Health and Environment , Japan.
Kimiko
K
Kawano
Kumamoto Prefectural Meat Inspection Office , Japan.
Kazutoshi
K
Matsumoto
Okinawa Prefectural Institute of Health and Environment , Japan.
Jun
J
Kudaka
Kyoto Prefectural Institute of Public Health and Environment , Japan.
Norio
N
Asai
Yamaguchi Prefectural Institute of Public Health and Environment , Japan.
Junko
J
Yabata
Yamaguchi Prefectural Institute of Public Health and Environment , Japan.
Kiyoshi
K
Tominaga
Department of Bacteriology I , National Institute of Infectious Diseases , Tokyo , Japan ; Division of Microbiology , National Institute of Health Sciences , Tokyo , Japan.
Jun
J
Terajima
Department of Bacteriology I , National Institute of Infectious Diseases , Tokyo , Japan.
Tomoko
T
Morita-Ishihara
Department of Bacteriology I , National Institute of Infectious Diseases , Tokyo , Japan.
Hidemasa
H
Izumiya
Department of Genomics and Bioenvironmental Science, Frontier Science Research Center , University of Miyazaki , Japan.
Yoshitoshi
Y
Ogura
Infectious Disease Surveillance Center , National Institute of infectious Diseases , Tokyo , Japan.
Takehito
T
Saitoh
Interdisciplinary Research Organization , University of Miyazaki , Japan.
Atsushi
A
Iguchi
National Agriculture and Food Research Organization , National Institute of Animal Health , Ibaraki , Japan.
Hideki
H
Kobayashi
Division of Microbiology , National Institute of Health Sciences , Tokyo , Japan.
Yukiko
Y
Hara-Kudo
Department of Bacteriology I , National Institute of Infectious Diseases , Tokyo , Japan.
Makoto
M
Ohnishi
Reiko
R
Arai
Masao
M
Kawase
Yukiko
Y
Asano
Nanami
N
Asoshima
Kazuki
K
Chiba
Ichiro
I
Furukawa
Toshiro
T
Kuroki
Madoka
M
Hamada
Seiya
S
Harada
Takashi
T
Hatakeyama
Takashi
T
Hirochi
Yumiko
Y
Sakamoto
Midori
M
Hiroi
Kanda
K
Takashi
Kazumi
K
Horikawa
Kaori
K
Iwabuchi
Mitsuhiro
M
Kameyama
Hitomi
H
Kasahara
Shinya
S
Kawanishi
Koji
K
Kikuchi
Hiroyuki
H
Ueno
Tomoko
T
Kitahashi
Yuka
Y
Kojima
Noriko
N
Konishi
Hiromi
H
Obata
Akemi
A
Kai
Tomomi
T
Kono
Takayuki
T
Kurazono
Masakado
M
Matsumoto
Yuko
Y
Matsumoto
Yuhki
Y
Nagai
Hideki
H
Naitoh
Hiroshi
H
Nakajima
Hiromi
H
Nakamura
Kunihiko
K
Nakane
Keiko
K
Nishi
Etsuko
E
Saitoh
Hiroaki
H
Satoh
Mitsuteru
M
Takamura
Yutaka
Y
Shiraki
Junichi
J
Tanabe
Keiko
K
Tanaka
Yuki
Y
Tokoi
Jun
J
Yatsuyanagi
EHEC; HUS; O157; clade; stx