Abstract: OBJECTIVE To observe and compare the phylogenetic types, multilocus sequence typing (MLST), drug resistance genes and virulence genes between the Escherichia coli isolates causing simple urinary tract infection and the isolates causing mixed bloodstream and urinary tract infections. METHODS The E. coli strains that were simultaneously isolated from submitted blood and urine specimens were retrospectively collected from The First Medical Center of Chinese PLA General Hospital from 2018 to 2023. The strains were divided into the simple urinary tract infection group and the concurrent bloodstream and urinary tract infection group according to the isolation site. The phylogenetic types, MLST and carrying rates of drug resistance genes and virulence genes were analyzed by whole genome sequencing. The antimicrobial susceptibility rates were compared between the two groups of E. coli strains. RESULTS There were totally 103 strains of E. coli in the simple urinary tract infection group and 21 strains in the concurrent bloodstream and urinary tract infection group. The type B2 (47.58%) was the predominant phylogenetic type among the 124 strains of E. coli, and ST131 was dominant among the MLST. With the regard to the β-lactams resistance genes in the E. coli strains, the carrying rate of bla_CTX-M family gene was 52.38% in the concurrent bloodstream and urinary tract infection, 66.02% in the simple urinary tract infection; for the quinolones resistance-related mutations, the carrying rate of gyrA mutation was 85.71% in the concurrent bloodstream and urinary tract infection group, 92.23% in the simple urinary tract infection group. The result of analysis of virulence factors showed that the carrying rates of P fimbriae, secreted autotransporter toxin, cytotoxic necrotizing factor-1, and Toll/interleukin-1 receptor (TIR) domain protein were higher in the concurrent bloodstream and urinary tract infection group than in the simple urinary tract infection(P＜0.05). CONCLUSIONS The E. coli strains that carry the virulence factors such as P fimbriae, secreted autotransporter toxin, cytotoxic necrotizing factor-1, and TIR domain protein may play an important role in the process of invasion from urinary tract infection to bloodstream infection.