El Solh N, Allignet J
National Reference Center for Staphylococci, Unité des Staphylocoques, Institut Pasteur, Paris, France.
Drug Resist Updat. 1998;1(3):169-75. doi: 10.1016/s1368-7646(98)80036-8.
Streptogramin and related antibiotics are mixtures of two compounds, A and B (e.g. Dalfopristin and Quinupristin), particularly against Gram-positive bacteria. Staphylococci resistant to these mixtures are always resistant to the A compounds but are not necessarily resistant to the B compounds. Resistance to A compounds and to the mixtures is conferred by acetyltransferases or ATP-binding proteins via unknown mechanisms. Several genes encoding each of the two categories of protein have been characterized and regularly detected on plasmids. Genes encoding lactonases, which inactivate B compounds, have been occasionally detected on these plasmids. Staphylococci which harbour plasmids conferring resistance to A compounds should not be treated with the mixtures even if they appear susceptible in vitro. Indeed, susceptibility to the mixtures of staphylococci carrying resistance to A compounds has often been attributed to partial loss of the plasmids conferring this resistance. When staphylococci are constitutively resistant to B compounds, the in vitro activities of the mixtures should be evaluated, because they are better correlated than MICs with their efficacy in therapy.
链阳菌素及相关抗生素是两种化合物A和B（如达福普汀和喹奴普汀）的混合物，对革兰氏阳性菌尤其有效。对这些混合物耐药的葡萄球菌总是对A类化合物耐药，但不一定对B类化合物耐药。乙酰转移酶或ATP结合蛋白通过未知机制导致对A类化合物及混合物产生耐药性。编码这两类蛋白质的几个基因已得到鉴定，并经常在质粒上检测到。在这些质粒上偶尔也检测到编码可使B类化合物失活的内酯酶的基因。携带对A类化合物耐药质粒的葡萄球菌，即使在体外显示敏感，也不应使用这些混合物进行治疗。事实上，携带对A类化合物耐药性的葡萄球菌对混合物的敏感性往往归因于赋予这种耐药性的质粒部分丢失。当葡萄球菌对B类化合物呈组成型耐药时，应评估混合物的体外活性，因为与最低抑菌浓度相比，它们与治疗效果的相关性更好。
