[Use DNA techniques to detect tetracycline resistance genes in clinical strains]

Our purpose in the present report was to use DNA techniques to analyse the distribution of Tetracycline resistance determinants among Gram negative bacteria and different location in our country. 306 clinical isolates, 102 out of which were isolated from nosocomial infections in Beijing Union Medical College Hospital from 1981-1986, were identified by fifteen kinds of biochemical reaction. According to sensibility test results, the percentage of resistant to antibiotics was that: Tetracycline 100%, Ampicillin 81.4%, Cefazolin 28.4%, Gentamycin 56.9%, Chloramphenicol 59.8%, TMP-SMZ 57.2%, Erythromycin 91.5%. The result of colony hybridization was that TetB (on R222) occurred at 31.4%, followed by TetD (on RA1) at 25.2%, TetA (on RP1) at 12.4% and TetC (on pSC101) at 10.5%, 36.6% of isolates failed to hybridize to any of the probes, while 51.3% harbored one determinant, 7.5% harbored two, 2.9% three and 1.6% four. Strains from some location contained TetB and TetD were slightly higher than TetC and TetA. At high stringency conditions of hybridization, we were able to show cross reaction of determinant C with TetA DNA, but no reaction with TetB and TetD DNA.