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Antimicrobial Agents and Chemotherapy, July 1999, p. 1631-1637, Vol. 43, No. 7
0066-4804/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.

Topoisomerase Sequences of Coagulase-Negative Staphylococcal Isolates Resistant to Ciprofloxacin or Trovafloxacin

Donald T. Dubin,1,* Joseph E. Fitzgibbon,1,2 Massoumeh D. Nahvi,2 and Joseph F. John1,2

Department of Molecular Genetics and Microbiology1 and Division of Allergy, Immunology, and Infectious Diseases, and Department of Medicine,2 UMDNJ-Robert Wood Johnson Medical School, Piscataway, New Jersey 08854-5635

Received 14 December 1998/Returned for modification 31 January 1999/Accepted 19 April 1999

Coagulase-negative staphylococcal isolates (n = 188) were screened for susceptibility to oxacillin, ciprofloxacin, and trovafloxacin, a new fluoroquinolone. At an oxacillin concentration of >= 4 µg/ml, 43% were methicillin resistant; of these, 70% were ciprofloxacin resistant (MIC, >= 4 µg/ml). Of the methicillin-resistant, ciprofloxacin-resistant isolates, 46% were susceptible to <= 2 µg of trovafloxacin per ml and 32% were susceptible to <= 1 µg of trovafloxacin per ml. Sixteen isolates, including twelve that expressed fluoroquinolone resistance, were chosen for detailed analysis. Identification of species by rRNA sequencing revealed a preponderance of Staphylococcus haemolyticus and S. hominis among fluoroquinolone-resistant strains. Segments of genes (gyrA and grlA) encoding DNA gyrase and DNA topoisomerase IV were sequenced. Considerable interspecies variation was noted, mainly involving noncoding nucleotide changes. Intraspecies variation consisted of coding changes associated with fluoroquinolone resistance. As for S. aureus, ciprofloxacin resistance (MIC, >= 8 µg/ml) and increased trovafloxacin MICs (0.25 to 2 µg/ml) could be conferred by the combined presence of single mutations in each gyrA and grlA gene. Trovafloxacin MICs of >= 8 µg/ml also occurred, but these required an additional mutation in grlA.

* Corresponding author. Mailing address: Department of Molecular Genetics and Microbiology, UMDNJ-Robert Wood Johnson Medical School, 675 Hoes Ln., Piscataway, NJ 08854-5635. Phone: (732) 235-4643. Fax: (732) 235-5223. E-mail: dubin{at}umdnj.edu.

Antimicrobial Agents and Chemotherapy, July 1999, p. 1631-1637, Vol. 43, No. 7
0066-4804/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.


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