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Appl. Environ. Microbiol., Feb 1997, 703-709, Vol 63, No. 2
P Kuhnert, J Hacker, I Muhldorfer, AP Burnens, J Nicolet and J Frey
We describe a rational approach to simultaneously test Escherichia coli
strains for the presence of known virulence genes in a reverse dot blot
procedure. Specific segments of virulence genes of E. coli designed to have
similar hybridization parameters were subcloned on plasmids and
subsequently amplified by PCR as unlabeled probes in amounts sufficient to
be bound to nylon membranes. Various pathogenic isolates and laboratory
strains of E. coli were probed for the presence of virulence genes by
labeling the genomic DNA of these strains with digoxigenin and then
hybridizing them to the prepared nylon membranes. These hybridization
results demonstrated that besides the E. coli K-12 safety strain
derivatives, E. coli B and C strains are also devoid of genes encoding any
of the investigated virulence factors. In contrast, pathogenic E. coli
control strains, used to evaluate the method, showed typical hybridization
patterns. The described probes and their easy application on a single
filter were shown to provide a useful tool for the safety assessment of E.
coli strains to be used as hosts in biotechnological processes. This
approach might also be used for the identification and characterization of
clinically significant E. coli isolates from human and animal species.
Copyright © 1997, American Society for Microbiology
Detection system for Escherichia coli-specific virulence genes: absence of virulence determinants in B and C strains
Institute of Veterinary Bacteriology, University of Bern, Switzerland. Kuhnert@vbi.unibe.ch
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