Stable higher level FQN-resistant strains of porcine E. coli were obtained by serial passages on agar containing subinhibitory concentration of CIP from four sensitive strains WJPE3-2, MYPE1-4, MSPE6, WJPE2-1. The results showed that different times of MIC values of CIP were promoted by induce test were between 4-512. Furthermore, the MIC values of Enrofloxacin, Norfloxacin and Oxfloxacin of each induced strain were also enhanced to different times.
Counted the colony formed unit (CFU) and calculated the bactericidal rate of PLA2. The drug resistance of Staphylococcus aureus (S.aureus) induced by the PLA2 was observed in drug resistant inducing test.
Present study was designed to assess effects of low levels of ciprofloxacin on representative human gut bacteria and its resistance a in vitro gut model in which both the antibacterial and test strains were exposed to conditions by vibrating simulating the human gastrointestinal tract, and two resistance induction models with no digestion in gut.
Resistance against ciprofloxacin was induced in 1 Staphylococcus aureus control strain ATCC25923 and 3 clinical isolates by 1/2 MIC, and minimal inhibitory concentration(MIC) of ciprofloxacin against Staphylococcus aureus was determined with disk diffusion and agar dilution susceptibility tests.