Influence of the decrease in ciprofloxacin susceptibility and the presence of human serum on the in vitro susceptibility of Streptococcus pneumoniae to five new quinolones

• Published in: Journal of antimicrobial chemotherapy Vol. 48; no. 6; pp. 907 - 909
• Main Authors: Balcabao, I. P., Alou, L., Aguilar, L., Gomez-Lus, M. L., Giménez, M. J., Prieto, J.
• Format: Journal Article
• Language: English
• Published: Oxford Oxford University Press 01.12.2001; Oxford Publishing Limited (England)
• Subjects: Anti-Infective Agents - blood; Anti-Infective Agents - pharmacology; Antibacterial agents; Antibiotics. Antiinfectious agents. Antiparasitic agents; Biological and medical sciences; Ciprofloxacin - blood; Ciprofloxacin - pharmacology; Drug Resistance, Bacterial - physiology; Humans; Medical sciences; Pharmacology. Drug treatments; Streptococcus pneumoniae - drug effects; Streptococcus pneumoniae - isolation & purification; Human; Drug susceptibility test; Moxifloxacin; In vitro; Biological activity; Streptococcus pneumoniae; Streptococcaceae; Gemifloxacin; Fluoroquinolone derivatives; Medium effect; Minimum inhibitory concentration; Clinafloxacin; Bacteria; Micrococcales; Serum; Antibacterial agent; Ciprofloxacin; Quinolone derivatives
• ISSN: 0305-7453; 1460-2091; 1460-2091
• DOI: 10.1093/jac/48.6.907

Sixty recent Streptococcus pneumoniae isolates with different susceptibilities to ciprofloxacin (14 with MIC 0.5 mg/L, 10 with MIC 1 mg/L, eight with MIC 2 mg/L, 11 with MIC 4 mg/L and 17 with MIC ≥8 mg/L) were tested against five new quinolones using Todd–Hewitt broth with and without 80% serum. The final inoculum was 5 × 105 cfu/mL. Gemifloxacin and clinafloxacin exhibited the lowest MIC90 values and resistance rates (percentage above and defined breakpoint) with and without serum for strains with a ciprofloxacin MIC of ≥4 mg/L. Other quinolones tested were less active against strains with reduced ciprofloxacin susceptibility. The presence of serum did not affect susceptibility to moxifloxacin, but increased the resistance rates to other new quinolones for strains with high ciprofloxacin MICs.