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

267

228

Fluoroquinolone-resistant mutants were obtained in vitro from Staphylococcus aureus RN4220 by stepwise selection on increasing concentrations of ciprofloxacin. Results from sequence analysis of the quinolone resistance-determining region of GyrA and of the corresponding region of GrlA, the DNA topoisomerase IV subunit, showed an alteration of Ser-80 to Tyr (corresponding to Ser-83 of Escherichia coli GyrA) or Glu-84 to Lys in GrlA of both low-and high-level quinolone-resistant mutants. Second-step mutants were found to have, in addition to a mutation in grlA, reduced accumulation of norfloxacin or an alteration in GyrA at Ser-84 to Leu or Glu-88 to Lys. Third-step mutants derived from second-step mutants with reduced accumulation were found to have a mutation in gyrA. The results from this study demonstrated that mutations in gyrA or mutations leading to reduced drug accumulation occur after alteration of GrlA, supporting the previous findings

Section: Discussionmentioning

confidence: 80%

Analysis of gyrA and grlA mutations in stepwise-selected ciprofloxacin-resistant mutants of Staphylococcus aureus

Ferrero¹,

Cameron²,

Crouzet³

1995

267

228

“…Of these, mutations at Ser-83 and Asp-87 have been found with a higher frequency in quinolone-resistant E. coli clinical isolates than in susceptible isolates (35). Similar mutations have also been identified in quinolone-resistant isolates of Staphylococcus aureus (12,19,24,30), Campylobacter jejuni (36), and Pseudomonas aeruginosa (21). Specific mutations in the gyrB gene also seem to be associated with quinolone resistance (35,37,39), although in quinolone-resistant E. coli clinical isolates, the frequency is very low (35).…”

mentioning

confidence: 76%

Mutation in the gyrA gene of quinolone-resistant clinical isolates of Acinetobacter baumannii

Vila

Ruiz

Goñi

et al. 1995

177

120

The gyrA gene mutations associated with quinolone resistance were determined in 21 epidemiologically unrelated clinical isolates of Acinetobacter baumannii. Our studies highlight the conserved sequences in the quinolone resistance-determining region of the gyrA gene from A. baumannii and other bacteria. All 15 isolates for which the MIC of ciprofloxacin is Ն4 g/ml showed a change at Ser-83 to Leu. Six strains for which the MIC of ciprofloxacin is 1 g/ml did not show any change at Ser-83, although a strain for which the MIC of ciprofloxacin is 1 g/ml exhibited a change at Gly-81 to Val. Although it is possible that mutations in other locations of the gyrA gene, the gyrB gene, or in other genes may also contribute to the modulation of the MIC level, our results suggest that a gyrA mutation at Ser-83 is associated with quinolone resistance in A. baumannii.

“…The first mechanism involves alterations in DNA gyrase, which generally result in high-level quinolone resistance (MIC, >16 ,ug/ml). Several point mutations in the gyrA gene, which is located in the SmaI-G fragment of the chromosome, have been identified (8,33). A second mechanism involves the drug efflux system encoded by the norA gene (19,20,37).…”

Section: Materuils and Methodsmentioning

confidence: 99%

“…Unfortunately, there have been increasing numbers of reports of ciprofloxacin resistance in both animals and humans with S. aureus infections (3,12). The mechanisms of resistance include a spontaneous single-step chromosomal mutation, resulting in alterations in the A sub-unit of DNA gyrase, an active efflux system that prevents net drug accumulation mediated by the norA gene, and low-level resistance mediated by the cfx-ofr locus, whose mechanism has not been investigated (8,19,20,26,28,33,34,37). The emergence of resistance to ofloxacin has been reported only in Japan (11,19,28).…”

mentioning

confidence: 99%

Pharmacodynamics of levofloxacin, ofloxacin, and ciprofloxacin, alone and in combination with rifampin, against methicillin-susceptible and -resistant Staphylococcus aureus in an in vitro infection model

Kang

Rybak

McGrath

et al. 1994

The pharmacodynamic properties of levofloxacin (an optically active isomer of ofloxacin), ofloxacin, and ciprofloxacin, alone and in combination with rifampin, were evaluated over 24 to 48 h against clinical isolates of methicillin-susceptible and -resistant Staphylococcus aureus (MSSA 1199 and MRSA 494, respectively) energy-dependent efilux process mediated by the norA gene appeared to be responsible for the resistance observed. Our data suggest that with levofloxacin there is a more rapid onset of bactericidal activity than with ofloxacin or ciprofloxacin against MSSA 1199 and that the activity of levofloxacin is similar to that of ofloxacin but better than that of ciprofloxacin against MRSA 494. Resistance was noted only after exposure to the low dose of ciprofloxacin. Resistance to ofloxacin did not develop even when the pharmacokinetics of the drug were set to equal those of ciprofloxacin, suggesting that ofloxacin differs from ciprofloxacin irrespective of time of exposure. The resistance to ciprofloxacin that developed in our in vitro model may be mediated by the cfxc-ofr locus, which has been shown to be associated with low-level fluoroquinolone resistance. Overall, levofloxacin demonstrated potent bactericidal activity against S. aureus, without the emergence of resistance in our infection model. Quinolones dosed once daily were more effective than equivalent dosages administered twice daily. The addition of rifampin was not synergistic but prevented the emergence of ciprofloxacin resistance.