Affiliation:
1. National Reference Laboratory for Escherichia coli, Centre for Infectiology and Pathogen Characterization, Federal Institute for Risk Assessment (BfR), Diedersdorfer Weg 1, D-12277 Berlin, Germany
Abstract
ABSTRACT
We examined 219 Shiga toxin-producing
Escherichia coli
(STEC) strains from meat, milk, and cheese samples collected in Germany between 2005 and 2006. All strains were investigated for their serotypes and for genetic variants of Shiga toxins 1 and 2 (Stx1 and Stx2).
stx
1
or variant genes were detected in 88 (40.2%) strains and
stx
2
and variants in 177 (80.8%) strains. Typing of
stx
genes was performed by
stx
-specific PCRs and by analysis of restriction fragment length polymorphisms (RFLP) of PCR products. Major genotypes of the Stx1 (
stx
1
,
stx
1c
, and
stx
1d
) and the Stx2 (
stx
2
,
stx
2d
,
stx
2-O118
,
stx
2e
, and
stx
2g
) families were detected, and multiple types of
stx
genes coexisted frequently in STEC strains. Only 1.8% of the STEC strains from food belonged to the classical enterohemorrhagic
E. coli
(EHEC) types O26:H11, O103:H2, and O157:H7, and only 5.0% of the STEC strains from food were positive for the
eae
gene, which is a virulence trait of classical EHEC. In contrast, 95 (43.4%) of the food-borne STEC strains carried
stx
2
and/or mucus-activatable
stx
2d
genes, an indicator for potential high virulence of STEC for humans. Most of these strains belonged to serotypes associated with severe illness in humans, such as O22:H8, O91:H21, O113:H21, O174:H2, and O174:H21.
stx
2
and
stx
2d
STEC strains were found frequently in milk and beef products. Other
stx
types were associated more frequently with pork (
stx
2e
), lamb, and wildlife meat (
stx
1c
). The combination of serotyping and
stx
genotyping was found useful for identification and for assignment of food-borne STEC to groups with potential lower and higher levels of virulence for humans.
Publisher
American Society for Microbiology
Subject
Ecology,Applied Microbiology and Biotechnology,Food Science,Biotechnology