ACTA VETERINARIA ET ZOOTECHNICA SINICA ›› 2019, Vol. 50 ›› Issue (1): 143-150.doi: 10.11843/j.issn.0366-6964.2019.01.017

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Isolation and Identification of Streptococcus suis Causing Meningitis in Piglets

CHEN Shenshen1,2, MA Jiale1,2, ZHANG Xinfeng1,2, QU Xiangyang3, PAN Zihao1,2, YAO Huochun1,2*   

  1. 1. College of Veterinary Medicine, Nanjing Agricultural University, Nanjing 210095, China;
    2. OIE Reference Laboratory for Swine Streptococcus of Nanjing Agricultural University, Nanjing 210095, China;
    3. The Hog-rasing Department of Huanshan Group, Qingdao 266071, China
  • Received:2018-06-04 Online:2019-01-23 Published:2019-01-24

Abstract:

The purpose of this study was to isolate and identify pathogenic bacteria from brain tissues and other organs of piglets suffering from meningitis. The species and serotype of the isolated strain were identified by PCR and serum agglutination test. The ultrastructure of the isolated strain was observed by transmission electron microscope, and the sequence type (ST) was determined by multilocus sequence typing tests (MLST). Minimal inhibitory concentration (MIC) was determined to analyze the antibiotic resistance of the isolated strain, while the virulence was detected by mice infection experiments. Results were as follows:a strain of Streptococcus suis was isolated from the brain tissue of piglets with meningitis which belongs to serotype 9 and named WH1609. The result of electron microscope showed that WH1609 had capsular structure. The result of MLST showed that WH1609 belonged to a new ST. WH1609 was a multi-drug resistant strain but sensitive to vancomycin, penicillin and ampicillin. The LD50 of BALB/c mice infected with WH1609 was 1.89×102 CFU·mL-1, and histopathological observation showed that the infected mice had obvious lesion in brain tissue. All the results suggest that a virulent strain of Streptococcus suis 9 isolated from the brain tissue of piglets suffering from meningitis exhibited a 105 times higher LD50 than that of other Streptococcus suis virulent strains, which is of great value to the study of the molecular mechanism meningitis caused by Streptococcus suis.

Key words: Streptococcus suis, meningitis, serotype 9, isolation, identification

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