| The paper is divided into 2 sections.The first section elaborated the study on the drug resistance, the specific kind, the de-gree and the mechanism in Ureaplasma urealyticum to tetracyclines. By means of micro -volume of broth dilution, MIC of 7 kinds from 3 classes of antimicrobial agents were determined . There was increasing rate of Uu strains resistant to tetracycline. These strains also showed lower susceptibility to minocycline and doxycycline. The inhibitory efficacy of Azithromycine and erythromycine in macrolides are the best ones,and fluoroquinolones are next to them. No Uu strain simultaneously resistant to the above 3 classes of antibitics was found in our study, which suggested other anti - mycoplasma agents should be substituted for the patients with clinical symptoms and the drug resistant strains.The mechanism to tetracycline resistance in Uu bases on the presence of drug resistant determinant(tet M), so PCR technique for tet M detection was developed,by which tet M determinant with 10-8μg of template DNA can be detected sensitively, rapidely and on large scale .The positive detection rate of tet M was 71.4% in Uu isolates.The detection rates in high - risk population from Guangdong, Shanghai, Kunming and Nanjing were 47.14.%, 30. 83% ,33.60% and 26.04%, respectively.The PCR product of standard strains was labelled to the probe and 93.3% positive hybridized signals were obtained. Uu - DNA extracts from Uu strains with MIC≥16μg/ml could also be detected on the dot blot by the probe. After digestion with Taq - 1 restriction endonuclease, fragments with 190 bp, 130 bp and 77 bp were produced, but some different fragment patterns were observed, which suggested that there may be some variation of tet M nucleotide sequences in Uu strains. The variation of tet M gene sequences may be helpful for epidemiologic study and may provide the information and reference for surveillanc of drug resistant strains in our country.
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