Objective: The objectives of this study were to compare some virulence factors’ presence and determine of phylogenetic groups of commensal and infectious Escherichia coli strains in neutropenic patients.
Methods: Two hundred twenty-eight nonrepetitive E. coli strains isolated between January 2003 and December 2008 mainly from feces and urine from neutropenic patients were studied. Six virulence factors (Intimin, enterohemolysin, Shiga-like toxin, siderophore, enterotoxin, and adhesin) were detected by amplifying the corresponding genes (eaeA, ehxA, stx, iutA, ast1, and aaf/I) from DNA by polymerase chain reaction. The phylogenetic group to which the E. coli strains belonged was determined by a polymerase chain reaction–based method for strains hosting virulence genes.
Results: Eighty strains, among the 228 strains, carried 1 or more virulence genes, including 59 commensal strains and 21 infectious strains. The statistical study showed no significant difference in the distribution of these genes between commensal and infectious strains. As far as the strains carrying the concerned virulence genes (80 isolates), 35% were of group A, 29% were of group D, 27% were of group B1, and 9% were of group B2. B2 and D groups were significantly more frequent among infectious strains. Phylogenetic group B2 isolates were the most sensitive to antibiotics, whereas resistance to quinolones and trimethoprim-sulfamethoxazole was higher among phylogenetic group A strains.
Conclusions: Our study showed that there was no significant difference in the distribution of the studied virulence genes between commensal and infectious strains. Phylogenetic groups D and B2 were more frequent among infectious strains, and resistance to quinolones and trimethoprim-sulfamethoxazole was higher among phylogenetic group A strains.