Abstract:To determine the relationship of the drug resistance of tetracyclines of Ureaplasma urealyticus and the distribution of the resistance gene tetM,the in vitro susceptibility to tetracycline and minocycline of 84 strains of U.urealyticus from clinical isolates was determined by broth microdilution method,and based on the susceptibility tested,the resistance gene tetM from 34 strains of U.urealyticus were amplified by PCR.It was found the MIC_(50)s to tetracycle and minomycyline were <(0.0625) mg/L and < 0.0125 mg/L respectively,and the MIC_(90)s to these two antibiotics were 0.125 mg/L and 1 mg/L respectively.Meanwhile,in these 34 strains of the non-resistant U.urealyticus,7 strains were to be detected tetM gene.With a higher MIC levels to tetracycline and minocyline in the tetM-positive strains than those in the tetM-negative strains,and this difference was quite significant(tetracycline: t=4.34,P=0.0001;minocycline: t=5.90,P<0.0001).It is evident that tetracycline and minocyclie can be used as the first-line antibiotics of choice to treat the U.urealyticus infection in Jiangsu province,with a better therapeutic effect when minocycline is used.In addition,the susceptible strains of U.urealyticud to tetracyclines harbor the resistance gene tetM that would influence upon the elevation of the MIC levels.