Epidemiology and molecular characterization of Cronobacter spp. isolated from 2013 to 2024 in Wenzhou

ObjectiveTo understand and master the infection status and molecular epidemiological characteristics of Cronobacter spp. in diarrhea patients in Wenzhou， and to provide a scientific basis for the prevention and control of foodborne diseases caused by Cronobacter spp. in this region.MethodsFrom 2013 to 2024， stool samples were collected from diarrhea patients with foodborne diseases in Wenzhou and tested for Cronobacter spp. Isolated Cronobacter strains underwent species identification， molecular serotyping， and whole-genome sequencing. Bioinformatics analyses were performed to assess genetic relatedness through cluster analysis， as well as to detect the presence of virulence-associated genes and antimicrobial resistance genes.ResultsA total 21 strains of Cronobacter spp. were detected in 1 816 samples， with a total isolation rate of 1.16%. In terms age distribution， the proportion of patients aged 18-60 years was 38.10%， and the proportion of patients under 1 year old was 33.33%. In terms of seasonal distribution， the detection rate in spring accounted for 38.10%， and that in summer accounted for 33.33%. Among the isolated strains， there were 14 strains of Cronobacter sakazakii， accounting for 66.67% of the total number of strains. Cronobacter sakazakii could be divided into 4 serotypes and 1 untyped strain， among which Csak O1 was the main serotype； Cronobacter malonaticus was divided into 2 serotypes， with Cmal O2 as the main serotype. After identification， the 21 strains of Cronobacter spp. were divided into 10 ST types and 8 clonal complexes （CC）， among which CC7 and CC4 were the main clonal complexes， and ST4 and ST201 were the main ST types. The gene annotation results of the 21 strains showed that all of them carried 17 genes related to motility， adhesion and invasiveness， etc. In addition， a total of 15 drug resistance genes were screened out， and most of the strains carried 11-14 drug resistance genes.ConclusionIn cases of foodborne diarrhea caused by Cronobacter spp. in Wenzhou， attention should be focused on Cronobacter spp. infections in infants. Csak O1 and Cmal O1 are the main serotypes， CC4 and CC7 are the main clonal complexes， and ST4 and ST201 are the main ST types.