title: Detection of grlA and gyrA mutations in 344 Staphylococcus aureus strains.
abstract: Mutations in the grlA and gyrA genes of 344 clinical strains of Staphylococcus aureus isolated in 1994 in Japan were identified by combinations of single-strand conformation polymorphism analysis, restriction fragment length analysis, and direct sequencing to identify possible relationships to fluoroquinolone resistance. Five types of single-point mutations and four types of double mutations were observed in the grlA genes of 204 strains (59.3%). Four types of single-point mutations and four types of double mutations were found in the gyrA genes of 188 strains (54.7%). Among them, the grlA mutation of TCC-->TTC or TAC (Ser-80-->Phe or Tyr) and the gyrA mutation of TCA-->TTA (Ser-84-->Leu) were principal, being detected in 137 (39.8%) and 121 (35.9%) isolates, respectively. The grlA point mutations of CAT-->CAC (His-77 [silent]), TCA-->CCA (Ser-81-->Pro), and ATA-->ATT (Ile-100 [silent]) were novel, as was the GAC-->GGC (Asp-73-->Gly) change in gyrA. A total of 15 types of mutation combinations within both genes were related to ciprofloxacin resistance (MIC > or = 3.13 microg/ml) and were present in 193 mutants (56.1%). Strains containing mutations in both genes were highly resistant to ciprofloxacin (MIC at which 50% of the isolates are inhibited [MIC50] = 50 microg/ml). Those with the Ser80-->Phe or Tyr alteration in grlA but wild-type gyrA showed a lower level of ciprofloxacin resistance (MIC50 < or = 12.5 microg/ml). Levofloxacin was active against 68 of 193 isolates (35.2%) with mutations at codon 80 of grlA in the presence or absence of a concomitant mutation at codon 73, 84, or 88 in gyrA (MIC < or = 6.25 microg/ml). The new fluoroquinolone DU-6859a showed good activity with 186 of 193 isolates (96.4%) for which the MIC was < or = 6.25 microg/ml.
authors.affiliation: New Product Research Laboratories I, Daiichi Pharmaceutical Co., Ltd., Tokyo, Japan.
authors.forename: T
authors.initials: T
authors.lastname: Wang
authors.forename: M
authors.initials: M
authors.lastname: Tanaka
authors.forename: K
authors.initials: K
authors.lastname: Sato
mesh_terms: D042462:4-Quinolones; D000890:Anti-Infective Agents / Q000494:pharmacology; D001426:Bacterial Proteins / Q000235:genetics*; D027081:DNA Gyrase; D027101:DNA Topoisomerase IV; D004250:DNA Topoisomerases, Type II / Q000235:genetics*; D005798:Genes, Bacterial / Q000235:genetics*; D006801:Humans; D008826:Microbial Sensitivity Tests; D017354:Point Mutation; D013211:Staphylococcus aureus / Q000187:drug effects / Q000235:genetics*
chemical_list: D042462:4-Quinolones; D000890:Anti-Infective Agents; D001426:Bacterial Proteins; D027101:DNA Topoisomerase IV; D027081:DNA Gyrase; D004250:DNA Topoisomerases, Type II