Molecular Characteristics of Spp. Responsible for Bloodstream Infections in a Tertiary Hospital in Nanjing, China, 2019-2021.

OBJECTIVE

To investigate the clinical and molecular characteristics of spp. causing bloodstream infections (BSIs) in our hospital.

METHODS

We studied 22 clinical isolates from BSIs and 16 from non-BSIs, performing antimicrobial susceptibility testing (AST) and whole genome sequencing (WGS). The analysis included serovars, antibiotic resistance genes (ARGs), virulence factors (VFs), sequence types (STs), plasmid replicons, and genetic relationships. We also assessed pathogenicity of the isolates causing BSIs through growth, biofilm formation, and anti-serum killing assays.

RESULTS

WGS analysis identified 13 serovars, with four responsible for BSIs. was the most prevalent serovar, involved in 19 (50.0%) cases. BSIs were caused by 17. Enteritidis, two . Typhimurium, two . Munster and one . Diguel. Of the 38 isolates, 27 (71.1%) exhibited high resistance to ampicillin, and 24 (63.2%) to ampicillin/sulbactam. Thirty-six types of ARGs were identified, with TEM-1B (n = 25, 65.8%) being the most frequent. Ten plasmid replicons were found; the combination of IncFIB(S)-IncFII(S)-IncX1 was the most common in . Enteritidis (94.7%). Fifteen STs were identified, among which ST11 was the most prevalent and clonally disseminated, primarily responsible for BSIs. A total of 333 different VFs were detected, 177 of which were common across all strains. No significant differences were observed between the BSI and non-BSI isolates in terms of resistance rates, ARGs, plasmid replicons, and VFs, except for seven VFs. No strong pathogenicity was observed in the BSI-causing isolates.

CONCLUSION

BSIs were predominantly caused by clonally disseminated . Enteritidis ST11, the majority of which carried multiple ARGs, VFs and plasmid replicons. This study provides the first data on clonally disseminated . Enteritidis ST11 causing BSIs, highlighting the urgent need for enhanced infection control measures.