Abstract:

Objective To identify and analyze the pathogenic bacteria isolated from blood samples of patients，and to understand the etiology and molecular characteristics of Streptococcus suis type 14. Methods Mass spectrometry analysis and serum agglutination test were used for identification. The drug resistance was analyzed by microbroth dilution method，and polymerase chain reaction （PCR）was used to determine 7 main virulence genes. Genomic information was obtained by next generation sequencing，and average nucleotide identity（ANI），ST typing and drug resistance gene analysis were performed. Results The isolates showed agglutination reaction with Streptococcus suis type 14，but no agglutination reaction with Streptococcus suis type 2. PCR showed positive 16S rRNA，negative cps2J and positive cps14J. The isolate were sensitive to all 9 antibiotics，including vancomycin，except for erythromycin，azithromycin，tetracycline and clindamycin，which were resistant. Except for gapdh virulence gene negative，the 6 main virulence genes，mrp，fbps，sly，orf2，ef and gdh，were all positive. The sequencing results showed ST 1 type，and phylogenetic tree analysis showed that this isolate had a relationship with previous isolates from Shenzhen City and Guangxi Zhuang Autonomous Region. Conclusions The isolated pathogen is highly virulent isolate Streptococcus suis type 14 ST 1，which can cause complications such as sepsis，meningitis and pneumonia in patients. Currently，there are no relevant reports. Epidemic prevention and monitoring should be strengthened in epidemic areas to avoid the recurrence of cases.

Key words: Streptococcus suis, Identification, Virulence gene, Average nucleotide identity