Affiliation:
1. Centre National de Référence des Bactéries Anaérobies et du Botulisme, Institut Pasteur, Paris, France
Abstract
ABSTRACT
A triple-locus nucleotide sequence analysis based on toxin regulatory genes
tcdC, tcdR
and
cdtR
was initiated to assess the sequence variability of these genes among
Clostridium difficile
isolates and to study the genetic relatedness between isolates. A preliminary investigation of the variability of the
tcdC
gene was done with 57 clinical and veterinary isolates. Twenty-three isolates representing nine main clusters were selected for
tcdC, tcdR
, and
cdtR
analysis. The numbers of alleles found for
tcdC, tcdR
and
cdtR
were nine, six, and five, respectively. All strains possessed the
cdtR
gene except toxin A-negative toxin B-positive variants. All but one binary toxin CDT-positive isolate harbored a deletion (>1 bp) in the
tcdC
gene. The combined analyses of the three genes allowed us to distinguish five lineages correlated with the different types of deletion in
tcdC
, i.e., 18 bp (associated or not with a deletion at position 117), 36 bp, 39 bp, and 54 bp, and with the wild-type
tcdC
(no deletion). The
tcdR
and
tcdC
genes, though located within the same pathogenicity locus, were found to have evolved separately. Coevolution of the three genes was noted only with strains harboring a 39-bp or a 54-bp deletion in
tcdC
that formed two homogeneous, separate divergent clusters. Our study supported the existence of the known clones (PCR ribotype 027 isolates and toxin A-negative toxin B-positive
C. difficile
variants) and evidence for clonality of isolates with a 39-bp deletion (toxinotype V, PCR ribotype 078) that are frequently isolated worldwide from human infections and from food animals.
Publisher
American Society for Microbiology
Cited by
29 articles.
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