JAC Advance Access originally published online on September 30, 2003
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Journal of Antimicrobial Chemotherapy (2003) 52, 869-872
© 2003 The British Society for Antimicrobial Chemotherapy
Comparative activity of garenoxacin and other agents by susceptibility and time–kill testing against Staphylococcus aureus, Streptococcus pyogenes and respiratory pathogens
1 Dottorato di Ricerca in Scienze Farmacologiche e Fisiopatologia Respiratoria XVII° ciclo, Seconda Università degli Studi di Napoli, Napoli; 2 Dipartimento di Medicina Pubblica Clinica e Preventiva, Sezione Malattie Infettive, Seconda Università degli Studi di Napoli, Via D. Cotugno, 1, 80135, Napoli, Italy
Received 12 June 2003; returned 6 July 2003; revised 25 July 2003; accepted 27 July 2003
Objectives: Garenoxacin is a novel des-F(6)quinolone that has shown excellent antimicrobial activity against a wide range of clinically important microorganisms. In this study, its activity was examined, in comparison with that of other antimicrobial agents, by susceptibility and time–kill testing against Staphylococcus aureus, Streptococcus pyogenes and respiratory pathogens.
Methods: Overall, 200 bacterial strains were tested. The antimicrobial activity of garenoxacin was compared with that of ciprofloxacin, levofloxacin, moxifloxacin, amoxicillin, co-amoxiclav, cefuroxime, cefotaxime, ceftriaxone, imipenem, erythromycin and clarithromycin. In addition, the bactericidal activity of garenoxacin, moxifloxacin, levofloxacin and ciprofloxacin was evaluated by time–kill analysis against four strains each of staphylococci [two methicillin-susceptible (MSSA) and two methicillin-resistant (MRSA)], pneumococci (two penicillin-susceptible and two penicillin-resistant) and Streptococcus pyogenes (two erythromycin-susceptible and two erythromycin-resistant). Antibiotics were tested at concentrations 1–8 x MIC.
Results: MIC90 values of garenoxacin for the MSSA and MRSA strains were 0.03 and 2 mg/L, respectively. Among all the quinolones tested, garenoxacin yielded the lowest MIC values against all pneumococci (MIC90 0.12 mg/L) irrespective of macrolide resistance; the rank order of activity was garenoxacin> moxifloxacin>levofloxacin>ciprofloxacin. Excellent activity was shown also against Haemophilus influenzae (MIC90 
0.03 mg/L) and Moraxella catarrhalis (MIC90 0.03 mg/L). Ninety percent of S. pyogenes were inhibited at garenoxacin concentrations equal to 0.25 mg/L, its activity not being influenced by macrolide susceptibility. Garenoxacin was rapidly bactericidal against staphylococci, producing a 
3 log10 decrease in viable counts (cfu/mL) within 3 h at 4 x MIC, whereas a moderate, slower killing rate was observed versus streptococci.
Conclusions: This investigational des-F(6)quinolone represents a promising alternative for the treatment of respiratory tract infections.
Keywords: new fluoroquinolones, Gram-positive, bactericidal activity
* Corresponding author. Tel: +39-081-566-62-18; Fax: +39-081-566-62-03; E-mail: silvanoesposito{at}libero.it