Comparison of antibiotic resistance and molecular characteristics of Escherichia coli isolated from patients with UTI, ASB, and uropathic bloodstream infection.

Background: Escherichia coli (E. coli) could cause asymptomatic bacteriuria (ASB), urinary tract infections (UTIs), and bloodstream infections (BSIs). However, the characteristics of antibiotic resistance patterns and molecular features of E. coli strains among these three patient groups have not been clarified. Methods: Three patient groups were prospectively and consecutively enrolled, including: the BSI-B group (UTI with concurrent bacteremia), the UTI-U group (UTI without bacteremia), and the ASB-U group (asymptomatic bacteriuria). All isolated strains were confirmed as E. coli by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. Antibiotic susceptibility testing was performed against 18 agents using VITEK 2 Compact system with AST-GN13 cards. Additionally, next-generation sequencing was employed to characterize multi-locus sequence typing, phylogenetic groups, serotypes, and virulence factors. Results: There were 50 cases for each group enrolled in this study. The UTI-U isolates demonstrated significantly higher resistance rates to aztreonam (28.00% vs. 8.00%), ceftazidime (20.00% vs. 4.00%), cefepime (16.00% vs. 2.00%), and gentamicin (30.00% vs. 12.00%) compared to the BSI-B group (P < 0.05). Phylogenetic group B2 and sequence type ST131 predominated in the BSI-B and UTI-U groups, whereas ST1193 was predominant in the ASB-U group. Virulence gene analysis revealed a higher prevalence of exotoxin (hlyABCD and cnf1) and adherence (papBCDEFGHJK) genes in both the BSI-B and UTI-U groups compared to ASB-U (P < 0.05). Additionally, the BSI-B group uniquely displayed a higher carriage of the nutritional/metabolic genes iroBCDEN. Conclusion: E. coli isolates from different clinical sources showed variations in antimicrobial resistance and molecular characteristics, which would be helpful for UTI patients' management.