Shales S W, Chopra I, Ball P R
J Gen Microbiol. 1980 Nov;121(1):221-9. doi: 10.1099/00221287-121-1-221.
The basis of tetracycline resistance mediated by TetA determinants and joint resistance to tetracycline and minocycline coded by TetB determinants was investigated. The TetA class of determinants was represented by those carried on plasmids pSC101, RP1 and pIP7 and TetB by Tn10. The relationships between expression of tetracycline and minocycline resistance and accumulation of these antibiotics suggest that there are three mechanisms of plasmid-determined resistance conferring (1) about a 10- to 20-fold increase in resistance to tetracycline that is not associated with decreased antibiotic accumulation, (2) a 4- to 7-fold increase in resistance to tetracycline that is associated with decreased drug accumulation, and (3) about a 2- to 3-fold increase in resistance to both tetracycline and minocycline that is not associated with decreased accumulation of either antibiotic. Mechanism 1 was coded by the tetracycline resistance determinant of pSC101 (TetA), mechanisms 1 and 2 by the determinants in RP1 and pIP7 (TetA) and all three mechanisms by Tn10 (TetB).
对由TetA决定簇介导的四环素抗性以及由TetB决定簇编码的对四环素和米诺环素的联合抗性的基础进行了研究。TetA类决定簇由携带在质粒pSC101、RP1和pIP7上的那些决定簇代表，而TetB由Tn10代表。四环素和米诺环素抗性的表达与这些抗生素的积累之间的关系表明，存在三种由质粒决定的抗性机制：（1）对四环素的抗性增加约10至20倍，这与抗生素积累减少无关；（2）对四环素的抗性增加4至7倍，这与药物积累减少有关；（3）对四环素和米诺环素的抗性增加约2至3倍，这与两种抗生素的积累减少均无关。机制1由pSC101的四环素抗性决定簇（TetA）编码，机制1和2由RP1和pIP7中的决定簇（TetA）编码，所有三种机制由Tn10（TetB）编码。
