Mutator natural Escherichia coli isolates have an unusual virulence phenotype.
A small percentage of natural Escherichia coli isolates (both commensal and pathogenic) have a mutator phenotype related to defects in methyl-directed mismatch repair (MR) genes. We investigated whether there was a direct link between the mutator phenotype and virulence by (i) studying the relationships between mutation rate and virulence in a mouse model of extraintestinal virulence for 88 commensal and extraintestinal pathogenic E. coli isolates and (ii) comparing the virulence in mice of MR-deficient and MR-proficient strains that were otherwise isogenic. The results provide no support for the hypothesis that the mutator phenotype has a direct role in virulence or is associated with increased virulence. Most of the natural mutator strains studied displayed an unusual virulence phenotype with (i) a lack of correspondence between the number of virulence determinants and pathogenicity in mice and (ii) an intermediate level of virulence. On a large evolutionary scale, the mutator phenotype may help parasites to achieve an intermediate rate of virulence which mathematical models predict to be selected for during long-term parasite-host interactions.
Picard
B
B
Laboratoire de Microbiologie, Faculté de Médecine, Brest, Paris, France.
Duriez
P
P
Gouriou
S
S
Matic
I
I
Denamur
E
E
Taddei
F
F
D000818:Animals; D020137:Base Pair Mismatch; D004260:DNA Repair / Q000235:genetics*; D004926:Escherichia coli / Q000235:genetics / Q000472:pathogenicity*; D005260:Female; D051379:Mice; D009154:Mutation; D010641:Phenotype; D014774:Virulence