| Objective:In order to provide a scientific basis for dedicated research and development of new drugs to particular resistance pathogens and provide an experimental data for risk assessment of Streptococcus becoming drug-resistant, in vitro induction of drug resistance experiment were conduced and the changes of resistant gene and virulence were tested on two streptococcus strains。Methods:Broth microdilution method was used to determine the minimal inhibitory concentration (MIC) of anti microbial drugs to bacteria; Standard strains of Streptococcus agalactiae CVCC1886 and Streptococcus dysgalactiae CVCC3701 were selected to develop the in vitro induction of drug resistance experiment by the method of gradually increasing the drug concentration; Resistance genes and virulence genes of bacteria before and after the induction were detected by PCR; physiological-biochemical properties of the strains before and after the induction were compared by morphology observation; Changes in virulence of strains before and after induction were compared by LD50 test in mice.Results: 1.The Streptococcus agalactiae CVCC1886 and Streptococcus dysgalactiae CVCC3701 developed resistance against 7 kinds of antibiotics, respectively; 2.Resistance genes and virulence genes of Streptococcus dysgalactiae CVCC3701 were changed when treated by the penicillin, not by the others; 3.The growth of the Streptococcus dysgalactiae CVCC3701-penicillin were decreased compared to the Streptococcus dysgalactiae CVCC3701; 4.The mouse LD50 before and after the inducing experiment of streptococcus dysgalactiae CVCC3701 were 5.45×106CFU/mL and 5.82×108CFU/mL, respectively. Compared with the untreated bacteria, the bacterial virulence was reduced 1.1 x 102 times after the resistance induction. |
PDF Full Text Request