Analysis of antimicrobial sensitivity and resistant genes of Streptococcus suis

Objective To determine the antimicrobial resistance of Streptococcus suis (S.suis) and to identify the relevant resistance gene.Methods Api-strep biochemical identification was performed to identify 56 strains of S.suis isolated from Sichuan, Guangxi, Guizhou and Guangdong in 2005, 2006 and 2007.Microdilution method was employed for the analysis of antimicrobial sensitivity, and PCR detection of resistance genes was conducted.Results For the thirteen categories of antibiotic tested in the present study, sensitivity to penicillin, ampicilolin, cefotaxime, ceftriaxome, cefepime, meropenem, levofloxacin, chloramphenicol, erythromycin, azithromycin, clindamycin and vancomycin was revealed for the 56 strains, and resistance to tetracycline was noticed.PCR detection to filter the tetracycline resistance genes, tet(K)，tet(L)，tet(M)，tet(O) and tet(Q), revealed consistent presence of tet(M) in each strain.Conclusion S.suis strains might have acquired tet(M) gene through evolutionary process.The wide spread of tet(M) was assumed to be associated with the abuse of tetracycline addictives as a growth promoting factor in swine feeding.