In vitroassays for clinical isolates of sequence type 131Escherichia colido not recapitulatein vivoinfectivity using a murine model of urinary tract infection

Abstract

Sequence Type 131 isolates are a major cause of cystitis and pyelonephritis. Many studies rely solely on in vitro assays to screen for bacterial virulence factors associated with the pathogenicity of clinical isolates of E. coli. Few studies have compared in vitro findings to in vivo infectivity of clinical isolates. The purpose of this study was to evaluate the correlation between in vitro assays with the ability to cause cystitis and pyelonephritis in a murine model of urinary tract infection. In vitro assays were conducted according to published protocols and included: motility assays, biofilm formation, epithelial cell adhesion and invasion, and curli production. Twenty-one UPEC isolates of E. coli ST131 and non-ST131 were used for both in vivo and in vitro studies. Six mice per isolate were inoculated via urethral catheterization. CFUs were determined from bladder and kidneys. In vitro and in vivo correlations were evaluated by multiple linear regression analysis. Pairwise linear regressions showed trendlines with weak positive correlations for motility, adhesion, and invasion and weak negative correlations for hemagglutination, biofilm and curli production. The ability of E. coli ST131 and non-ST131 clinical isolates to cause cystitis and pyelonephritis varies among strains. The R2 Pearson Correlation value was less than ±0.5 for any pair, indicating little to no statistical association between in vitro and in vivo findings. These data show in vitro data are not predictive of the ability of ST131 E. coli to infect and/or cause disease in a mouse model.