Serotypes, drug resistance, and multilocus sequence types of Salmonella isolates in Suzhou

Abstract:

[Background] Salmonella is a zoonotic pathogen and one of the most common pathogens causing infectious diarrhea in humans. [Objective] To analyze the serotypes, drug resistance, and multilocus sequence types of 176 Salmonella strains isolated in Suzhou, 2023. [Methods] The serotypes of the isolates were identified by the slide agglutination method. The drug resistance was tested by the micro-broth dilution method. The multilocus sequence typing (MLST) was performed by whole genome sequencing, and the sequencing results were compared with PubMLST to obtain the sequence types (STs) of the strains. [Results] A total of 42 serotypes belonging to 9 serogroups were identified for the 176 Salmonella isolates. The dominant serotypes were Salmonella enteritidis (26.70%) and Salmonella typhimurium (18.75%). The resistance rate of the 176 strains to ampicillin was the highest (60.23%), followed by that to streptomycin (47.16%). All the strains were sensitive to ceftazidime/avibactam, meropenem, ertapenem, and amikacin. The multidrug resistance (MDR) of the 176 strains reached a rate of 57.39%, with 51 patterns (including 18 patterns involving penicillins+ β-lactam/ β-lactam inhibitor complex+cephalosporins). The 176 strains presented 43 STs, among which ST11, ST34, and ST19 were the top three, with the detection rates of 27.27%, 10.80% and 7.95%, respectively. [Conclusion] The Salmonella strains in Suzhou present diverse serotypes and STs. The dominant serotypes are S. enteritidis and S. typhimurium, and the dominant ST is ST11. The MDR phenomenon is serious and thus surveillance should be strengthened.