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Infect. Immun., Jun 1997, 2034-2040, Vol 65, No. 6
AG Goncalves, LC Campos, TA Gomes, J Rodrigues, V Sperandio, TS Whittam and LR Trabulsi
A total of 110 Escherichia coli strains of serogroup O119 were examined for
the presence of virulence properties characteristic of enteropathogenic E.
coli (EPEC). Three virulence patterns were distinguished based on the
detection of a chromosomal gene mediating intimate attachment (eaeA) and
plasmid DNA involved in localized adherence (EAF and bfpA). The first
pattern, represented by strains which hybridized with three gene probes,
was the most common (68%) and, with a single exception, included only
O119:H6 strains. Of these strains, 90% showed a typical localized adherence
(LA) pattern in HEp-2 cells and 96% were positive for intimate attachment
in a fluorescent- actin staining test with a 3-h incubation period. The
second pattern was represented by strains which hybridized with the eaeA
gene only. Most (89.5%) of these strains showed the LA phenotype but only
after 6 h of incubation (LA-like phenotype). The third pattern consisted of
strains which were positive for eaeA and bfpA but did not hybridize with
the EAF probe. Most (80%) of these strains exhibited the LA-like phenotype.
Analysis of several eaeA+ bfpA+ strains for the expression of the pilin
subunit (BfpA) of the bundle-forming pili demonstrated that all LA strains
expressed BfpA whereas the LA-like strains did not. The study of the clonal
relationships, carried out by multilocus enzyme electrophoresis in 79
representative strains, defined 11 distinct electrophoretic types (ETs).
ET1 included 66% of the strains, most of which displayed the eaeA+ bfpA+
EAF+ pattern and were serotyped as O119:H6 or O119:H-. The remaining 10 ETs
were each represented by no more than five strains and, with the exception
of ET8, included strains of a single serotype. The genetic relatedness of
the ETs revealed two main clusters, with most strains in cluster A having
the eaeA+ bfpA+ EAF+ combination and a O119:H6 serotype. Cluster B was
represented by atypical EPEC strains with only the eaeA+ and the eaeA+
bfpA+ virulence pattern.
Copyright © 1997, American Society for Microbiology
Virulence properties and clonal structures of strains of Escherichia coli O119 serotypes
Departamento de Microbiologia, Instituto de Ciencias Biomedicas, Universidade de Sao Paulo SP, Brazil.
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