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Antimicrobial Agents and Chemotherapy, November 2006, p. 3568-3579, Vol. 50, No. 11
0066-4804/06/$08.00+0     doi:10.1128/AAC.00641-06
Copyright © 2006, American Society for Microbiology. All Rights Reserved.

The Anti-Methicillin-Resistant Staphylococcus aureus Quinolone WCK 771 Has Potent Activity against Sequentially Selected Mutants, Has a Narrow Mutant Selection Window against Quinolone-Resistant Staphylococcus aureus, and Preferentially Targets DNA Gyrase{triangledown} ,{dagger}

Sachin S. Bhagwat, Lakshmi A. Mundkur, Shrikant V. Gupte, Mahesh V. Patel,* and Habil F. Khorakiwala

Wockhardt Research Center, Aurangabad, India

Received 25 May 2006/ Returned for modification 2 July 2006/ Accepted 12 August 2006

WCK 771 is a broad-spectrum fluoroquinolone with enhanced activity against quinolone-resistant staphylococci. To understand the impact of the target-level interactions of WCK 771 on its antistaphylococcal pharmacodynamic properties, we determined the MICs for genetically defined mutants and studied the mutant prevention concentrations (MPCs), the frequency of mutation, and the cidality against the wild type and double mutants. There was a twofold increase in the MICs of WCK 771 for single gyrA mutants, indicating that DNA gyrase is its primary target. All first- and second-step mutants selected by WCK 771 revealed gyrA and grlA mutations, respectively. The MICs of WCK 771 and clinafloxacin were found to be superior to those of other quinolones against strains with double and triple mutations. WCK 771 was also cidal for high-density double mutants at low concentrations. WCK 771 and clinafloxacin showed narrow mutant selection windows compared to those of the other quinolones. Against a panel of 50 high-level quinolone-resistant clinical isolates of staphylococci (ciprofloxacin MIC ≥ 16 µg/ml), the WCK 771 MPCs were ≤2 µg/ml for 68% of the strains and ≤4 µg/ml for 28% of the strains. Our results demonstrate that gyrA is the primary target of WCK 771 and that it has pharmacodynamic properties remarkably different from those of quinolones with dual targets (garenoxacin and moxifloxacin) and topoisomerase IV-specific quinolones (trovafloxacin). WCK 771 displayed an activity profile comparable to that of clinafloxacin, a dual-acting quinolone with a high affinity to DNA gyrase. Overall, the findings signify the key role of DNA gyrase in determining the optimal antistaphylococcal features of quinolones.

* Corresponding author. Mailing address: Wockhardt Research Centre, D-4, Chikalthana, MIDC Area, 431210, Aurangabad (MS) India. Phone: 91 240 2483854. Fax: 91 240 2489219. E-mail: mpatel{at}wockhardt.com.

{dagger} Supplemental material for this article may be found at http://aac.asm.org/.

{triangledown} Published ahead of print on 28 August 2006.

Antimicrobial Agents and Chemotherapy, November 2006, p. 3568-3579, Vol. 50, No. 11
0066-4804/06/$08.00+0     doi:10.1128/AAC.00641-06
Copyright © 2006, American Society for Microbiology. All Rights Reserved.



This article has been cited by other articles:

  • Bhagwat, S. S., McGhee, P., Kosowska-Shick, K., Patel, M. V., Appelbaum, P. C. (2009). In Vitro Activity of the Quinolone WCK 771 against Recent U.S. Hospital and Community-Acquired Staphylococcus aureus Pathogens with Various Resistance Types. Antimicrob. Agents Chemother. 53: 811-813 [Abstract] [Full Text]  


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