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

A portion of the gyrA gene from amino acid codons 67 to 129 was sequenced in 34 methiciflin-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. Methicillin-resistant Staphylococcus aureus (MRSA) in-fections pose serious therapeutic difficulties in that few antimicrobial agents are effective against this pathogen (1). At one time, ciprofloxacin held promise for the treatment of these infections (1, 19). Presently, however, widespread resistance of MRSA to ciprofloxacin has developed in many centers and the mechanism of this resistance has provoked much study