Biological characteristics and PFGE typing of 12 strains of human Streptococcus suis type 2 in Zhongshan City / 公共卫生与预防医学

ABSTRACT

Objective To study the biological characteristics of clinical isolates of human infected Streptococcus suis type 2 in Zhongshan City from 2016 to 2019 and classify the strains using pulse-field gel electrophoresis (PFGE), and to provide a scientific basis for clinical prevention and treatment of porcine streptococcus suis disease. Methods Twelve strains of Streptococcus suis type 2 were collected from 2016 to 2019 and identified by automatic bacterial identification instrument. The carrying status of five major virulence genes of Streptococcus suis was detected by nucleic acid and protein analyzer, including capsular polysaccharide (cps2J), lysozyme-releasing protein (mrp), hemolysin (sly), glutamate dehydrogenase (gdh), and extracellular factor (ef). The susceptibility of Streptococcus suis to 12 kinds of commonly used antibiotics was determined by the broth microdilution method, and the homology analysis was carried out by PFGE method. Results Twelve strains of Streptococcus suis type 2 were divided into four virulence genotypes, mainly mrp-/sly+/ef+/cps2J+/gdh+ (6strains) and mrp-/sly-/ef+/cps2J+/gdh+(4strains). Drug susceptibility test results showed that 12 strains of Streptococcus suis type 2 were resistant to erythromycin, tetracycline and clindamycin, and they all were multi-resistant strains. According to the classification results of PFGE, the 12 strains were classified into 7 PFGE types based on 100% similarity coefficient. The PFGE band types of Streptococcus suis in the same year had high homology. Conclusion The virulence genotypes of 12 clinical isolates of human infected type 2 Streptococcus suis in Zhongshan from 2016 to 2019 are diverse, and the strains are resistant to multiple antibiotics. Most strains in the same year are the same clone strains. PFGE genotypes are not correlated with virulence genotypes and drug resistance spectrum.