Multi‑locus sequence and drug resistance analysis of Salmonella infection in children with diarrhea in Guangdong to identify the dominant ST and cause of antibiotic‑resistance.

Multi-locus sequence typing (MLST) can be used to analyze the homology among the drug resistance gene cassettes in and determine the prevalence. Information extracted using this technique can provide a theoretical basis for hospitals to devise protocols to control infections. The aim of the present study was to investigate the possible association between drug resistance and integrons in clinical isolates of from human fecal samples. Therefore, in the present study, 52 clinical fecal isolates of non-duplicate (i.e., not genome contamination) were harvested from children with diarrhea and used for bacterial identification using biochemical tests, drug susceptibility analysis by antibiotic susceptibility testing and serotype identification using an agglutination assay. In total, seven housekeeping genes ( and ) were amplified and sequenced using MLST, before sequence alignment was performed against the Pub MLST database to determine the sequence-typed (ST) strains and construct genotypic evolutionary diagrams. Subsequently, the 52 strains were subdivided into 11 serotypes and 11 sequence types. The dominant subtypes were found to be ST34 and ST19, which were diversely distributed. However, no new subtypes were found. Although the serotypes, including ST19, ST29, ST34, ST40, ST11, ST27, ST469, ST365, ST1499, ST413 and ST588, were closely associated with the MLST subtype, they did not correspond entirely. The detection rate of class I integrons was 38.46% (20/52), but no class II and III integrons were detected. The variable regions of three of 20 class I integrons were found to be amplified, whereas nine gene cassettes, including , , (, , , , , and , were associated with drug resistance. These data suggest that Class I integrons are important factors underlying drug resistance in , which may serve a role in the spread of drug resistance and warrant specific focus. In addition, MLST typing and serotyping should be applied cooperatively in epidemiological research.