Susceptibility of Streptococcus pyogenes to azithromycin, clarithromycin, erythromycin and roxithromycin in vitro

• Published in: Journal of medical microbiology Vol. 43; no. 5; pp. 386 - 391
• Main Authors: van Asselt, G. J, Sloos, J. H, Mouton, R. P, van Boven, C. P. A, van de Klundert, J. A. M
• Format: Journal Article
• Language: English
• Published: Reading Soc General Microbiol 01.11.1995; Society for General Microbiology
• Subjects: Anti-Bacterial Agents - pharmacology; Antibacterial agents; Antibiotics. Antiinfectious agents. Antiparasitic agents; Azithromycin - pharmacology; Biological and medical sciences; Clarithromycin - pharmacology; Erythromycin - pharmacology; Humans; Medical sciences; Microbial Sensitivity Tests; Netherlands; Pharmacology. Drug treatments; Roxithromycin - pharmacology; Streptococcus pyogenes; Streptococcus pyogenes - drug effects; Netherlands; Europe; Streptococcaceae; Antibiotic; Minimum bactericidal concentration; Drug susceptibility test; Minimum inhibitory concentration; Bacteria; Micrococcales; Streptococcus pyogenes; Erythromycin; Antibacterial agent; In vitro; Macrolide
• ISSN: 0022-2615; 1473-5644
• DOI: 10.1099/00222615-43-5-386

Department of Medical Microbiology, University Hospital Leiden, PO Box 9600, 2300 RC Leiden. The Netherlands * Present address and address for correspondence: Department of Medical Microbiology, Westeinde Hospital, Lijnbaan 32, 2512 VA Den Haag, The Netherlands. Received April 22, 1995 Accepted April 25, 1995 The susceptibility of 180 clinical isolates of Streptococcus pyogenes from six regions of The Netherlands to the macrolide antibiotics azithromycin, clarithromycin, erythromycin and roxithromycin was analysed. The results of a microbroth MIC method, the E-test method and a disk diffusion assay were compared, and the MBC determined. In addition, the susceptibility to erythromycin of 436 clinical isolates of S. pyogenes from the Leiden region was determined. The microbroth MIC90s of azithromycin, clarithromycin, erythromycin and roxithromycin for group A streptococci were 0·5 mg/L. Erythromycin had the lowest MIC90 (0·09mg/L). The MIC data obtained with the E-test method suggested that clarithromycin and erythromycin had slightly higher anti-streptococcal activity than azithromycin and roxithromycin in vitro. MICs obtained with the E-test were lower than those found with the microbroth method. Only minor discrepancies were observed among the three methods. The MBC50 for both clarithromycin and erythromycin was 0·75 mg/L and 5·0mg/L for azithromycin and roxithromycin. None of the 180 strains and two of the collection of 436 strains (0·5%) were resistant to erythromycin and the other macrolides tested; MICs ranged from 1 to 16 mg/L. The erythromycin-resistant strains showed an inducible type of macrolide-lincosamide-streptogramin B (MLS) resistance.