Maiden M C
Division of Bacteriology, National Institute for Biological Standards and Control, Herts, United Kingdom.
Clin Infect Dis. 1998 Aug;27 Suppl 1:S12-20. doi: 10.1086/514917.
Some transformable bacteria have acquired target-mediated antibiotic resistance by horizontal genetic exchange of fragments of chromosomal genes. The resistant strains express variants of the antibiotic target that are metabolically active but exhibit a lowered affinity for the antibiotic. The alleles encoding these resistant proteins are mosaics comprising DNA derived from the host and other bacteria, often members of a different species. Examples include penicillin-resistant penicillin-binding proteins (PBPs) in Streptococcus pneumoniae and the pathogenic Neisseria species and sulfonamide-resistant dihydropterate synthase in Neisseria meningitidis. Distinct mosaic alleles encoding antibiotic resistance have arisen on multiple occasions, indicating the mobility of chromosomal genes in these species. Mosaic genes can arise at any chromosomal locus, and S. pneumoniae organisms with high-level penicillin resistance have acquired mosaic PBP genes at three bacterial bpb loci. Furthermore, horizontal genetic exchange permits movement of alleles among bacterial lineages, increasing the opportunities for the spread of antibiotic resistance.
一些可转化细菌通过染色体基因片段的水平基因交换获得了靶点介导的抗生素抗性。抗性菌株表达抗生素靶点的变体，这些变体具有代谢活性，但对抗生素的亲和力降低。编码这些抗性蛋白的等位基因是嵌合体，由来自宿主和其他细菌（通常是不同物种的成员）的DNA组成。例子包括肺炎链球菌和致病性奈瑟菌属中的耐青霉素青霉素结合蛋白（PBPs），以及脑膜炎奈瑟菌中的耐磺胺二氢蝶酸合酶。编码抗生素抗性的不同嵌合等位基因已多次出现，表明这些物种中染色体基因的流动性。嵌合基因可出现在任何染色体位点，具有高水平青霉素抗性的肺炎链球菌生物体已在三个细菌bpb位点获得了嵌合PBP基因。此外，水平基因交换允许等位基因在细菌谱系之间移动，增加了抗生素抗性传播的机会。
