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.