Pathogenic features of urinary Escherichia coli strains causing Asymptomatic Bacteriuria during Pregnancy

Background: Asymptomatic bacteriuria is one of the common problems in pregnancy. Pyelonephritis, preterm labor and low birth weight infants have been associated with bacterial infection. Urinary tract infection (UTI) during pregnancy is frequently associated with complications. An observational cross-sectional study including investigated the prevalence of virulence genes, antimicrobial resistance, and its relationship with phylogenetic groups among E. coli strains isolated from pregnant women with asymptomatic bacteriuria who referred to Hafez hospital, Shiraz, Iran. Material and Methods A total of 300 urine samples were screened for Escherichia coli strains. Susceptibility testing was determined by the disk-diffusion method. The phylogenetic groups and 13 virulence genes were identified by PCR. ESBL and AmpC producing isolates were detected using phenotypic methods. PCR was used to identify the bla TEM , bla SHV and bla CTXM genes in ESBL and AmpC-positive isolates. Results Our results revealed that among 300 urine samples, 105 (35%) were positive for E. coli . The data showed that the highest and the lowest resistance rates were observed against nalidixic acid (82.1%), and imipenem (2.8%), respectively. The prevalence of ESBLs and AmpC-β-lactamase, in the E. coli isolates was 41% and 9.5% respectively. bla CTXM was the commonest genotype (93%). Phylogenetic group distribution was as follow: B1 2.8%, A 14.2%, B2 61.9%, and D 4.6%. Our result showed that most of the virulence genes belonged to group B2 and also several virulence genes such as hlyA , cnf-1 , and papGII genes were positively associated with group B2. Conclusion Among E. coli strains isolated from patients with UTIs, different features phylogroups, with special virulence factors, could cause severe infection. Awareness about the Virulence patterns distribution among Phylogenetic groups of UPEC could greatly aid in confine and prevent the development of lethal infection caused by these strains.