Analysis of phylogenetic typing, virulence genes and biofilm phenotype of uropathogenic Escherichia coli isolates

  Objective  To analyze phylogenetic typing, virulence genes and biofilm phenotype of isolated uropathogenic Escherichia coli(UPEC)strains.

  Methods  Urine samples from patients with clinical urinary tract infection were collected for bacterial culture. The colonies with a colony number greater than 10⁵ CFU/mL after bacterial culture in urine were collected and then subjected to bacterial isolation. The UPEC isolates from suspected Escherichia coli strains were identified by Matrix Assisted Laser Desorption/Ionization technique (MALDI-Biotyper). Multiplex Polymerase Chain Reaction (PCR) was used to detect the phylogeny genes chuA, yjaA and DNA fragment TspE4.C2 of UPEC isolates. The distribution of nine virulence genes (fimH, tonB, ireA, fyuA, cnf-1, vat, hlyD, ompR and phoU) was detected by PCR. The biofilm formationability of UPEC isolates was quantitatively determined by crystal violet staining.

  Results  A total of 42 UPEC isolates were selected, and the main phylogeny typing was B2 and D, accounting for 40.5% and 31.0%, respectively. Detection of nine virulence genes found that the fimH gene encoding type Ⅰ fimbriae had the highest detection rate (92.9%); the detection rate of iron-uptake related genes tonB, ireA and fyuA were 90.5%, 66.7% and 76.2%, respectively; among the three toxin-related genes, the detection rate of cnf-1 gene encoding cytotoxic necrosis factor was the highest (52.4%), was 21.4% for hemolysin encoding gene hlyD and 28.6% for vacuolating toxin gene vat; the detection rates of the other virulence genes such as ompR and phoU were lower than 30.0%. Our results showed that all the tested isolates could form biofilm, among which 16 isolates had strong biofilm formation ability (38.1%), 15 isolates had moderate biofilm formation ability (35.7%), and the remaining 11 strains had weak biofilm forming ability. Further analysis showed that the strong biofilm-forming strains mainly belonged to phylogenetic type B2, which possessed the higher numbers of virulence genes than that of the weak biofilm-forming strains (P < 0.05).

  Conclusion  The biofilm formation ability of UPEC clinical isolates is correlated with the phylogenetic types and the distribution virulence genes. This study will help to understand the biological characteristics of UPEC clinical isolates, especially the biofilm formation ability and virulence gene distribution, and could provide important references for the prevention and control of urinary tract infection.