title: Alterations in the DNA topoisomerase IV grlA gene responsible for quinolone resistance in Staphylococcus aureus.
abstract: A 4.2-kb DNA fragment conferring quinolone resistance was cloned from a quinolone-resistant clinical isolate of Staphylococcus aureus and was shown to possess a part of the grlB gene and a mutated grlA gene. S-80-->F and E-84-->K mutations in the grlA gene product were responsible for the quinolone resistance. The mutated grlA genes responsible for quinolone resistance were dominant over the wild-type allele, irrespective of gene dosage in a transformation experiment with the grlA gene alone. However, dominance by mutated grlA genes depended on gene dosage when bacteria were transformed with the grlA and grlB genes in combination. Quinolone-resistant gyrA mutants were easily isolated from a strain, S. aureus RN4220, carrying a plasmid with the mutated grlA gene, though this was not the case for other S. aureus strains lacking the plasmid. The elimination of this plasmid from such quinolone-resistant gyrA mutants resulted in marked increases in quinolone susceptibility. These results suggest that both DNA gyrase and DNA topoisomerase IV may be targets of quinolones and that the quinolone susceptibility of organisms may be determined by which of these enzymes is most quinolone sensitive.
authors.affiliation: Discovery Research Laboratories II, Dainippon Pharmaceutical Co., Ltd., Suita, Osaka, Japan.
authors.forename: J
authors.initials: J
authors.lastname: Yamagishi
authors.forename: T
authors.initials: T
authors.lastname: Kojima
authors.forename: Y
authors.initials: Y
authors.lastname: Oyamada
authors.forename: K
authors.initials: K
authors.lastname: Fujimoto
authors.forename: H
authors.initials: H
authors.lastname: Hattori
authors.forename: S
authors.initials: S
authors.lastname: Nakamura
authors.forename: M
authors.initials: M
authors.lastname: Inoue
mesh_terms: D000595:Amino Acid Sequence; D001483:Base Sequence; D027101:DNA Topoisomerase IV; D004250:DNA Topoisomerases, Type II / Q000032:analysis / Q000235:genetics*; D004352:Drug Resistance, Microbial / Q000235:genetics; D005798:Genes, Bacterial / Q000235:genetics*; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D009154:Mutation; D016366:Open Reading Frames; D010957:Plasmids / Q000235:genetics; D015363:Quinolones / Q000737:chemistry*; D017422:Sequence Analysis, DNA; D013211:Staphylococcus aureus / Q000187:drug effects / Q000201:enzymology / Q000235:genetics*
chemical_list: D015363:Quinolones; D027101:DNA Topoisomerase IV; D004250:DNA Topoisomerases, Type II