Gensberg K, Jin Y F, Piddock L J
Department of Infection, Medical School, University of Birmingham, Edgbaston, UK.
FEMS Microbiol Lett. 1995 Oct 1;132(1-2):57-60. doi: 10.1111/j.1574-6968.1995.tb07810.x.
In order to study the role of gyrB in antibiotic resistance in post-ciprofloxacin therapy fluoroquinolone-resistant clinical isolates of Salmonella typhimurium, plasmid pBP548, which contains the Escherichia coli gyrB gene, was used in complementation studies. In a heterodiploid strain, the wild-type (quinolone sensitive) allele is dominant over the resistant allele therefore, eleven clinical isolates were complemented with gyrB encoded on pBP548. Only one transformant, L18pBP548, exhibited increased susceptibility to the quinolones nalidixic acid, ciprofloxacin and sparfloxacin. The amino acid sequence of the gyrase B protein from a wild-type and the pre-therapy S. typhimurium (deduced from the nucleotide sequence) was identical to that of E. coli from codons 436 to 470; however, a point mutation was identified in codon 463 of gyrB of the quinolone-resistant post-therapy isolate L18, giving rise to an amino acid substitution of serine to tyrosine.
为了研究gyrB在环丙沙星治疗后鼠伤寒沙门氏菌氟喹诺酮耐药临床分离株的抗生素耐药性中的作用，在互补研究中使用了含有大肠杆菌gyrB基因的质粒pBP548。在异源二倍体菌株中，野生型（喹诺酮敏感）等位基因相对于耐药等位基因是显性的，因此，用pBP548上编码的gyrB对11株临床分离株进行了互补。只有一个转化体L18pBP548对喹诺酮类药物萘啶酸、环丙沙星和司帕沙星的敏感性增加。野生型和治疗前鼠伤寒沙门氏菌（从核苷酸序列推导）的gyrase B蛋白的氨基酸序列在第436至470位密码子与大肠杆菌相同；然而，在喹诺酮耐药的治疗后分离株L18的gyrB的第463位密码子中发现了一个点突变，导致丝氨酸被酪氨酸取代的氨基酸替换。
