Evaluation of toxin genes and phylogenetic groups of uropathogenic Escherichia coli isolates from children with urinary tract infections

Uropathogenic Escherichia coli (UPEC) is the first and most common cause of urinary tract infection in children. The severity of urinary infection depends on the virulence factors or the phylogroup of the infecting strain. The aim of this study was to identify the patterns of toxin genes and its relationship with different phylogenetic groups in UPEC isolates from children with urinary tract infections. One hundred and twenty-one UPEC isolates from pediatric patients (≥2 and <14 years old) with urinary tract infections were evaluated. The hlyA, cnf1, sat and pic toxin genes were determined by PCR. Phylogenetic typing was done according to the methods described by Clermont et al. Association between virulence genes and phylogenetic groups was analyzed. The obtained results indicate 114 (94.2%) of all UPEC isolates carried at least one of the studied genes. The most frequent toxin gene was sat (n=112, 92.6%), followed by pic (n=23, 19.0%), hlyA (n=3, 2.5%) and cnf1 (n=3, 2.5%). A significant association between the presence of hlyA (P=0.046), and cnf1 (P=0.002) genes and pyelonephritis infection was observed. The results of phylogenetic grouping showed majority of UPEC isolated were phylogroup A followed by phylogroup B2. The majority of UPEC strains causing pyelonephritis infection were from phylogroups D and B2, respectively. Both UPEC strains carried three virulence genes, related to phylogroup D. The findings of the present study showed that UPEC strains isolated from complicated urinary tract infections of children in our region belong to phylogroups D and B2, and the cnf1 toxin gene can help clinicians as potential clinical predictors in predicting the occurrence of upper UTI caused by the mentioned strains and managing patients.