Objective: This study aimed to investigate the prevalence of Escherichia coli  ST131 and molecularly characterize the O25b-ST131 and O16-ST131 subgroups among urinary tract infection (UTI) E. coli  isolates from women in central China. We also assessed the clinical characteristics and outcomes of infections caused by E. coli  ST131.
Methods: Between January 2014 and December 2015, a total of 216 consecutive, non-repetitive E. coli  isolates were recovered from UTI urine samples from women in Changsha, China. All isolates were analyzed for phylogenetic groups, antimicrobial resistance and virulence genotypes. ST131 clonal groups were identified using PCR and characterized using O serotyping, CTX-M genotypes, fimH , gyrA , and parC  alleles, fluoroquinolone resistance genes and pulsed-field gel electrophoresis (PFGE). Clinical data were obtained from medical records.
Results: Overall, 41 (19.0%) of 216 E. coli  isolates were identified to contain ST131 strains, among which 27 were O25b-ST131 strains and 14 were O16-ST131 strains. The clinical characteristics and outcomes of the ST131 group did not differ significantly from those of the non-ST131 group, except for the presence of urinary stones (43.9% vs 27.4%, P =0.039). Ciprofloxacin resistance was found to be significantly higher in O25b-ST131 isolates than O16-ST131 isolates (96.3% vs 14.3%, P <0.001). The majority of O25b-ST131 isolates belonged to fimH  30 (92.6%), followed by fimH  41 (3.7%) and fimH  27 (3.7%). O25b-H  30 and O25b-H  41 isolates were resistant to ciprofloxacin, and possessed gyrA 1AB/parC  1aAB combination. All of the O16-S131 isolates were found to belong to fimH  41, and of which, two of the ciprofloxacin-resistant strains harbored gyrA 1AB/parC  3A combination. Three PFGE clusters, consisting of 38 (92.7%) isolates, with more than 70% similarity were identified.
Conclusion: The O25b and O16 sub-lineages have emerged as an important group of E. coli  ST131 in UTI isolates from women in China. UTI patients with a history of urinary stones may need to be particularly vigilant against ST131 infection.
Keywords: E. coli , ST131, fimH -based subclones, fluoroquinolone resistance, urinary tract infection