To analyze the distribution of serotypes and antimicrobial resistance of clinical Salmonella isolates from multiple centers across China.

Non-duplicate Salmonella strains were retrospectively collected from 53 hospitals in 26 provinces between January 1, 2021, and December 31, 2022. All isolates were confirmed by mass spectrometry, with serotyping performed using serum agglutination tests and antimicrobial susceptibility testing conducted via the broth microdilution method.

A total of 605 Salmonella strains were included, comprising 42 serotypes. S.typhimurium (37.7%) and S.enteritidis (34.0%) were the predominant serotypes. Antimicrobial susceptibility testing revealed the highest resistance rate to ampicillin (80.8%), while resistance to levofloxacin (8.8%), imipenem (1.2%), ertapenem (0.8%), and meropenem (0.5%) was below 10%. In terms of serotype distribution, S.typhimurium exhibited higher resistance rates than S.enteritidis to ampicillin (88.6%), ciprofloxacin (11.8%), levofloxacin (7.5%), chloramphenicol (52.6%), ceftazidime (16.7%), ceftriaxone (32.9%), minocycline (62.3%), and trimethoprim-sulfamethoxazole (45.2%). By age group, isolates from individuals aged 6-17 years showed higher resistance to ampicillin-sulbactam (59.1%) and minocycline (45.5%), while those from patients over 65 years had higher resistance to imipenem (5.1%) and ertapenem (3.4%). Regarding specimen type, stool-derived isolates demonstrated higher resistance to ampicillin (82.5%), chloramphenicol (40.8%), minocycline (41.0%), and trimethoprim-sulfamethoxazole (37.8%) compared to other sources. Among departments, isolates from the hematology unit showed the highest resistance to levofloxacin (22.2%). Geographically, strains from Central China had the highest resistance to ciprofloxacin (19.0%), those from South China exhibited the highest resistance to chloramphenicol (59.6%) and minocycline (59.6%), and isolates from East China showed the highest resistance to trimethoprim-sulfamethoxazole (51.2%). The overall multidrug resistance rate among Salmonella isolates was 44.8% (271/605).

Clinically isolated Salmonella strains in China display diverse serotype distributions, with S.typhimurium and S.enteritidis being the predominant types. High overall antimicrobial resistance and widespread multidrug resistance were observed. Resistance rates to commonly used antimicrobials varied by age, specimen type, department, and geographic region. Antimicrobial therapy should be guided by susceptibility testing results to mitigate the development of resistance.