In vitro Antibacterial Activities of New Fluoroquinolones against Clinical Isolates of Haemophilus influenzae with Ciprofloxacin-Resistance-Associated Alterations in GyrA and ParC

Abstract
The in vitro antimicrobial activities of new fluoroquinolones were tested against quinolone-resistant Haemophilus influenzae of clinical isolates. The nucleotide sequences of the gyrA and parC genes from three ciprofloxacin-resistant strains of Haemophilus influenzae (MIC, 1.56-6.25 microg/ml) were determined. The gyrase was purified from the clinical isolates, and the inhibitory activities of quinolones against the enzyme were tested. These strains possessed at least one amino acid substitution in each of the GyrA (asparagine at residue 88 (Asp-88) to Tyr, Ser-84 to Leu or Ser-84 to Leu and Asp-88 to Asn) and ParC (Glu-88 to Lys). The antibacterial activity of olamufloxacin against the resistant strains was most potent compared with other quinolones, and the inhibitory activities correlated with quinolone resistance of these strains. These results warrant the clinical effects of new types of fluoroquinolones, such as olamufloxacin, against respiratory tract and otolaryngology infections caused by ciprofloxacin-resistant H. influenzae.

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