Molecular Characteristics and Risk Factors of Bloodstream Infection Caused by Escherichia coli ST131 in Southeast China.

BACKGROUND: E. coli ST131 is the predominant lineage among extraintestinal pathogenic E. coli isolates worldwide and is an important pathogen associated with all kinds of human infections. The aim of this study was to investigate the prevalence and molecular characteristics of E. coli ST131 and non-ST131 isolates that cause bloodstream infections and evaluate the risk factors for E. coli ST131. METHODS: A total of 103 E. coli isolates associated with bloodstream infection were collected between August 2014 and August 2015 at a Chinese university hospital. The isolates were classified into ST131 and non-ST131 E. coli groups by multilocus sequence typing. Phylogenetic analysis, susceptibility testing, virulence genotyping, PCR-based O typing, and pulsed-field gel electrophoresis (PFGE) were performed, and the clinical features of patients in both groups were compared. RESULTS: Overall, 12 isolates (11.7%) were identified as ST131 isolates, including 10 O25b-ST131 (83.3%) and 2 O16-ST131 (16.7%) clones. All 103 E. coli isolates were divided into four phylogenetic groups: B2 was the predominant phylogenetic group (n = 39, 37.9%), and it was followed in descending order by D (n = 33, 32.0%), A (n = 20, 19.4%), and B1 (n = 11, 10.7%). Compared with the non-ST131 isolates, the E. coli ST131 isolates harbored more virulence factors and were associated with a significantly higher incidence of urinary tract infection (p = 0.040) and a significantly greater length of hospital stay (p = 0.045). According to PFGE analysis, the molecular features of the E. coli ST131 isolates were highly diverse, and there was no dominant clone. CONCLUSIONS: The ST131 isolates collected from Southeast China in this study exhibited strong virulence and multiple drug resistance, and the main serotype was O25b-ST131. Therefore, future studies should focus on O16-ST131 subclones in order to better understand the prognosis of patients with bloodstream infection caused by E. coli ST131.

Antimicrobial Resistance, Genetic Diversity and Virulence Genes of Salmonella Typhimurium Isolated in Infant with Acute Diarrhea in Fuzhou, China, 2015 - 2017.

BACKGROUND: S. Typhimurium was the dominant serovar in an infant in Fuzhou, China. There have been few comprehensive studies on Salmonella typhimurium in infants in China. METHODS: We conducted a retrospective study on 30 Salmonella typhimurium from 3,200 fecal samples of infants with acute diarrhea from 2015 to 2017. Thirty S. Typhimurium strains were tested for antimicrobial susceptibility and characterized for virulence genes. Pulsed-field gel electrophoresis (PFGE) was also applied for comparison of genetic relatedness. RESULTS: All of the strains harbored misL, orfL, pipD, prgH, sifA, sopB, sitC, spiC, and invA genes. The other three gene distributions in the strains are different. Strains subtyped into 4 virulotypes (VP1-VP4), the most common virulence profile was VP3, accounting for 63.3% of the strains. The resistance to ciprofloxacin and ceftriaxone was 26.7%. The proportion of MDR isolates is approximately 90.0%. Sixteen different antimicrobial resistance patterns were observed and the most frequent resistance type was antibiotype 13 (resistance to streptomycin, tetracycline, amoxicillin), occurring in 43.3% of the isolates. Regarding PFGE, 30 isolates of S. Typhimurium showed genetic diversity, while no predominant PFGE patterns were observed in S. Typhimurium. Moreover, no correlation between virulence profiles or antibiotic patterns and PFGE clusters was observed. With one exception, VP1 which harbors pefA showed more diversity than the other virulence profiles among PFGE profiles. CONCLUSIONS: Our study provided valuable information on virulence gene content, antibiotic resistance, and genetic diversity of S. Typhimurium isolated from infant with acute diarrhea in Fuzhou, China.