Isolation, identification and drug sensitivity test of a strain of Streptococcus suis type 16 strain from Guangdong Province

DENG Rusen;LI Li;LI Jiaming;LUO Shicheng;ZHANG Haoquan;YAN Guangzhi;CHEN Shengnan;HUANG Liangzong;School of Life Science and Engineering, Foshan University;Zhongshan City Henglan Town Urban Management and Rural Agriculture Bureau;Guangdong Findergene Technology Co., Ltd.;

Streptococcus suistype 16;;isolation and identification;;virulence gene;;pathogenicity;;drug susceptibility test

In order to determine the cause of piglet death in a large-scale pig farm in Jiangmen City, Guangdong Province, the experiment co-llected the hearts, spleens, lungs, synovial fluids, brains, lymph nodes and other tissues of sick pigs for virus detection, bacterial isolation and identification. Purification culture, Gram staining observation, biochemical identification, bacterial species identification and sequencing analysis, serotype identification, virulence gene detection, animal test and drug sensitivity test were carried out on the isolated bacteria. The results showed that the isolated strain grew well on blood agar and showed α-hemolysis; gram-positive cocci were observed by microscopy, which showed typical chain arrangement; the biochemical characteristics were consistent with Streptococcus suis; target bands with sizes of 1 500 bp and 688 bp were obtained by PCR amplification, and the homology between the strain and Streptococcus suis was more than 99%, which was in the same branch with Streptococcus suis in phylogenetic tree, being Streptococcus suis type 16. The virulence factor genotype of the strain was fbps~+/orf~+/sly~+/gapdh~+/epf~-/mrp~-, which could cause the death of NIH mice and have strong virulence. The strain was sensitive to 9 drugs, amoxicillin/clavulanic acid, penicillin, cefotaxime, cefradine, ceftriaxone, gentamicin, spectinomycin, enrofloxacin and florfenicol, and was resistant to four drugs, neomycin, compound sulfamethazole, doxycycline and tilmicosin. Amoxicillin was used for group therapy and achieved good results. The results suggested that the piglets in this pig farm were infected with Streptococcus suis type 16, and penicillin antibacterial drugs could be used for clinical treatment.