Isolation and detection of Shiga toxin-producing Escherichia coli in clinical stool samples using conventional and molecular methods.
The isolation of Shiga toxin-producing Escherichia coli (STEC) other than serogroup O157 from clinical stool samples is problematic due to the lack of differential phenotypic characteristics from non-pathogenic E. coli. The development of molecular reagents capable of identifying both toxin and serogroup-specific genetic determinants holds promise for a more comprehensive characterization of stool samples and isolation of STEC strains. In this study, 876 stool samples from paediatric patients with gastroenteritis were screened for STEC using a cytotoxicity assay, commercial immunoassay and a conventional PCR targeting Shiga-toxin determinants. In addition, routine culture methods for isolating O157 STEC were also performed. The screening assays identified 45 stools presumptively containing STEC, and using non-differential culture techniques a total of 20 O157 and 22 non-O157 strains were isolated. These included STEC serotypes O157 : H7, O26 : H11, O121 : H19, O26 : NM, O103 : H2, O111 : NM, O115 : H18, O121 : NM, O145 : NM, O177 : NM and O5 : NM. Notably, multiple STEC serotypes were isolated from two clinical stool samples (yielding O157 : H7 and O26 : H11, or O157 : H7 and O103 : H2 isolates). These data were compared to molecular serogroup profiles determined directly from the stool enrichment cultures using a LUX real-time PCR assay targeting the O157 fimbrial gene lpfA, a microsphere suspension array targeting allelic variants of espZ and a gnd-based molecular O-antigen serogrouping method. The genetic profile of individual stool cultures indicated that the espZ microsphere array and lpfA real-time PCR assay could accurately predict the presence and provide preliminary typing for the STEC strains present in clinical samples. The gnd-based molecular serogrouping method provided additional corroborative evidence of serogroup identities. This toolbox of molecular methods provided robust detection capabilities for STEC in clinical stool samples, including co-infection of multiple serogroups.
Gilmour
Matthew W
MW
National Microbiology Laboratory, Winnipeg, MN, Canada.
Chui
Linda
L
Department of Laboratory Medicine and Pathology, University of Alberta, Edmonton, AB, Canada.|Alberta Provincial Laboratory for Public Health, Edmonton, AB T6G 2J2, Canada.
Chiu
Theodore
T
Alberta Provincial Laboratory for Public Health, Edmonton, AB T6G 2J2, Canada.
Tracz
Dobryan M
DM
National Microbiology Laboratory, Winnipeg, MN, Canada.
Hagedorn
Kathryn
K
Alberta Provincial Laboratory for Public Health, Edmonton, AB T6G 2J2, Canada.
Tschetter
Lorelee
L
National Microbiology Laboratory, Winnipeg, MN, Canada.
Tabor
Helen
H
National Microbiology Laboratory, Winnipeg, MN, Canada.
Ng
Lai King
LK
National Microbiology Laboratory, Winnipeg, MN, Canada.
Louie
Marie
M
Alberta Provincial Laboratory for Public Health, Edmonton, AB T6G 2J2, Canada.
D001431:Bacteriological Techniques / Q000379:methods*; D029968:Escherichia coli Proteins / Q000235:genetics / Q000378:metabolism; D005243:Feces / Q000382:microbiology*; D015964:Gene Expression Regulation, Bacterial / Q000502:physiology; D006801:Humans; D016133:Polymerase Chain Reaction; D054323:Shiga-Toxigenic Escherichia coli / Q000302:isolation & purification*
D029968:Escherichia coli Proteins