2015 Volume 50 Issue 1 Pages 8-15
luxS-mediated autoinducer-2 (AI-2) directly or indirectly regulates important physiologic function in a variety of bacteria, including bioluminescent effect, antimicrobial resistance, virulence factor control, biofilm structure stability and so on. In this study, the regulation of susceptibility to antimicrobials by luxS/AI-2 was investigated in Streptococcus agalactiae. A luxS- knockout mutant strain named SX1 was constructed by homologous recombination from S. agalactiae CNEP110823 (wild type strain), and a luxS-complementation strain named SX2 was constructed from SX1 through transducing a plasmid with the luxS gene and its promoter. Then the susceptibility to cefradine and norfloxacin of these two strains, SX1 exposed to AI-2 precursor molecule 4,5-dihydroxy-2,3-pentanedione (DPD) and the wild type strain was determined by viable bacterial counting. SX1 decreased susceptibility to cefradine and norfloxacin, SX2 returned the susceptibility to the same level as the wild type strain and DPD restored the susceptibility of SX1. The results indicate that luxS/AI-2 quorum sensing is involved in antimicrobial susceptibility in S. agalactiae, which may provide novel clues for antimicrobial therapy in the infection.
