Detection of gyrA gene mutations associated with ciprofloxacin resistance in methicillin-resistant Staphylococcus aureus: analysis by polymerase chain reaction and automated direct DNA sequencing.

A portion of the gyrA gene from amino acid codons 67 to 129 was sequenced in 34 methicillin-resistant Staphylococcus aureus strains (14 isolated in Minnesota, 10 isolated in Indiana, and 10 isolated in Tennessee). Twenty-eight of these strains were ciprofloxacin resistant. Sixteen of the strains contained a Ser----Leu mutation at codon 84; 3 contained strains a Ser----Ala mutation at codon 84; 3 strains contained two mutations, Ser----Leu at codon 84 and Ser----Pro at codon 85; and 6 strains contained a Glu----Lys mutation at codon 88. Six strains were wild type and ciprofloxacin susceptible. Several mutations from amino acid codons 84 through 88 can be associated with high-level quinolone resistance.