关键词: 猪链球菌, 氟喹诺酮类药物, parC基因, gyrA基因

Abstract: To detect the relationship between fluoroquinolone resistance and gyrA and parC gene mutation in Streptococcus suis. The MIC of 34 strains of Streptococcus suis were determined by microdilution. The genes encoding the quinolone-resistance determining region (QRDRs) of parC and gyrA in fluoroquinolone-susceptible and -resistant Streptococcus suis clinical isolates were identified and sequenced. Ser to Phe and Arg to Leu mutation at position 79 and 87 of the parC gene was detected in fluoroquinolone resistance S.suis, and Arg to Ser, or Ser to Arg mutations at the position 66 or 81 of gyrA gene were detected in 4 highly resistance strains; no amino acid changes in gyrA or parC were detected for 9 fluoroquinolonesusceptible strains，the mutations in both genes was found in the strains with MIC of fluoroquinolone higher than 32μg·L^-1. Mutations in parC gene result in low level resistance against fluoroquinolone,and high level resistance is resulted from the mutations in gyrA and parC both genes.

Key words: Streptococcus suis, fluoroquinolone, parC gene, gyrA gene