Virulence determinants, phylogenetic groups and fluoroquinolone resistance in Escherichia coli isolated from cystitis and pyelonephritis

Aim of the study

The aim of this study is to assess the relation between virulence genotype, phylogenetic group and susceptibility to fluoroquinolones and the urinary tract infection type including pyelonephritis and cystitis due to Escherichia coli.

Materials and methods

Between 2006 and 2007, 129 non-duplicate E. coli isolates from pyelonephritis (n = 56) and cystitis (n = 73) were prospectively collected. The antibiotic susceptibility was done by disk diffusion method. The phylogenetic groups, A, B1, B2 and D and 18 virulence genes were determined by multiplex PCR. Statistical analysis was done with the Pearson χ2 test, Mann-Whitney U-test, Kruskal-Wallis test and stepwise multivariable logistic regression analysis, P values below 0.05 were considered statistically significant.

Results

For the pyelonephritis group, sex ratio was 0.3, the median age for women was 30 years and for men it was 54 years. For the cystitis group, sex ratio was 0.4, the median age for women was 41.5 years and for men it was 67.8 years. Significant statistical correlations were found between pyelonephritis isolates and susceptibility to ciprofloxacin (P = 4 10^–5), papG allele II (P = 2 10^–6), hlyA (P = 10^–03), iroN (P = 0.04), iha (P = 0.03) and ompT (P = 0.03) virulence genes, high virulence score (P = 0.008) and B2 phylogenetic group (P = 0.03). In multivariate logistic regression analysis, papG II as predictor of pyelonephritis, no correlation could be established for the cystitis group.

Conclusion

Our findings argue for a direct link between pyelonephritis, virulence factors, susceptibility to fluroquinolones and B2 phylogenetic group among uropthogenic E. coli.