Characterization of nontyphoidal strains from a tertiary hospital in China: serotype diversity, multidrug resistance, and genetic insights.

OBJECTIVE

Nontyphoidal is a significant public health concern due to its ability to cause foodborne illnesses worldwide. This study aims to characterize the nontyphoidal strains isolated from patients in China.

METHODS

A total of 19 nontyphoidal strains were characterized through serovar identification, antimicrobial susceptibility testing (AST), biofilm formation assessment. Genetic relatedness was determined using pulsed-field gel electrophoresis (PFGE). WGS was employed to decipher the resistance mechanism and to contextualize the serovar Mbandaka strains among previously sequenced isolates in China. The biofilm associated gene was examined by PCR.

RESULTS

The predominant serovar identified was Enteritidis, followed by Mbandaka, Thompson, Livingston, Alachua, and Infantis. PFGE analysis indicated a notable genetic similarity among the Mbandaka isolates. Phylogenetic analysis suggested that these strains were likely derived from a single source that had persisted in China for over five years. One multidrug resistance (MDR) Enteritidis isolate carried a highly transferable IncB/O/K/Z plasmid with . One Thompson strain, harboring the operon in an IncX1 plasmid, isolated from cutaneous lesions, demonstrated robust biofilm formation. However, no loci were detected in other strains.

CONCLUSION

Our study emphasizes the importance of persisted surveillance and prompt response to infections to protect public health. The dissemination of -harboring IncB/O/K/Z plasmid and the spread of virulent operon among in China and other global regions warrant close monitoring.