1株产金属β-内酰胺酶的血清3型ST117猪链球菌的生物学特性OA

One Streptococcus strain was isolated from the lung tissue of diseased pigs,and its molecular typing identification was performed through morphological observation,16S rRNA gene sequencing,and multilocus sequence typing(MLST).The pathogenicity and drug resist-ance of the isolated strain were studied via mouse infection experiments,virulence gene screening,biofilm formation ability tests,and drug sensitivity tests on antibiotics and traditional Chinese medicines(TCMs).The results showed that the isolated strain was Gram-positive,with oval-shaped bacterial cells arranged in chains observed under electron microscopy.PCR and 16S rRNA gene phylogenetic tree analysis iden-tified it as Streptococcus suis serotype 3,designated as Streptococcus suis GZYZ0831.The sequence type of isolate GZYZ0831 was ST117,which carried five virulence genes:the surface antigen gene(sao),the bacterial transferrin-binding protein gene(Tbp),the glyceraldehyde-3-phosphate dehydrogenase gene(GAPDH),the virulence-associated sequence second open reading frame(orf2),and the muramidase-released protein gene(mrp);and which exhibited α-hemolysis.Infection in mice caused varying degrees of pathological lesions in multiple organs including the lungs,spleen,and liver.GZYZ0831 was a multidrug-resistant strain producing metallo-β-lactamases(MBLs),carry-ing the resistance genes blaTEM and tetO.It possessed resistance to 17 antibiotics,including azithromycin,erythromycin,clarithromycin,and gentamicin,but was sensitive to the Chinese herbal medicines Coptidis rhizoma and Isatidis radix.This study systematically analyzed the biological characteristics of Streptococcus suis serotype 3 ST117 strain,providing scientific basis for research on the pathogenic and drug re-sistance mechanisms of Streptococcus suis,and serving as reference for the formulation of TCMs prevention and control strategies against Strep-tococcus suis infection.