Antimicrobial resistance, serotypes, and virulence factors of Streptococcus suis isolates from diseased pigs.
Streptococcus suis isolates from diseased pigs were examined for susceptibility to nine antimicrobials, possession of virulence-associated factors (VFs), and distribution of serotypes. The association between antimicrobial resistance (AMR) and serotypes as well as VFs was subsequently assessed. Among the isolates investigated, serotype 2 (66.04%) was mostly prevalent, followed by serotypes 1 (23.27%), 9 (1.26%), and 7 (0.63%), whereas 14 isolates were untypable by the polymerase chain reaction typing method used. Analysis with pulsed-field gel electrophoresis revealed the isolates had diverse DNA macrorestriction patterns. The frequency of antimicrobial resistance among the S. suis isolates was higher than that reported from other countries. It is notable that multiple antimicrobial resistance (three or more antimicrobials) was observed with 98.73% of the S. suis isolates, and the dominant resistance phenotype was erythromycin-tilmicosin-clindamycin-chloramphenicol-levofloxacin-ceftiofur-kanamycin-tetracycline-penicillin (35.85%). The most prevalent VFs were those encoded by muramidase-released protein (61.64%), followed by suilysin (56.60%) and extracellular factor (46.54%). Presence of VFs and the possession of certain AMR phenotypes were significantly associated as determined by statistical analysis. Together, these findings indicate that the clinical S. suis isolates obtained from diseased pigs in China are genetically diverse, are resistant to multiple antibiotics of clinical importance, and carry known virulence factors.
College of Veterinary Medicine, National Reference Laboratory of Veterinary Drug Residues, South China Agricultural University, Guangzhou, China.
Lu-Lu
LL
Li
Xiao-Ping
XP
Liao
Jian
J
Sun
Yu-Rong
YR
Yang
Bao-Tao
BT
Liu
Shou-Shen
SS
Yang
Dong-Hao
DH
Zhao
Ya-Hong
YH
Liu
D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology; D002681:China; D024881:Drug Resistance, Bacterial; D016521:Electrophoresis, Gel, Pulsed-Field; D006460:Hemolysin Proteins / Q000494:pharmacology; D009113:Muramidase / Q000494:pharmacology; D010641:Phenotype; D012703:Serotyping / Q000379:methods; D017011:Streptococcus suis / Q000145:classification / Q000187:drug effects / Q000302:isolation & purification / Q000472:pathogenicity*; D013552:Swine / Q000382:microbiology*; D013553:Swine Diseases / Q000453:epidemiology* / Q000382:microbiology*; D037521:Virulence Factors / Q000235:genetics*
D000900:Anti-Bacterial Agents; D006460:Hemolysin Proteins; D037521:Virulence Factors; C104760:suilysin; D009113:Muramidase