In vitro antimicrobial activity of azithromycin, and its therapeutic efficacy in respiratory tract infections

Akira Watanabe, Satoru Shoji, Hiroshi Takahashi, Hiroaki Kikuchi, Toshihiro Nukiwa, Yoshihiro Honda, Yushi Nakai, Shigeo Takizawa

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    1 Citation (Scopus)


    The in vitro antimicrobial activity of azithromycin (AZM), a new azalide antimicrobial agent for oral use developed by Pfizer pharmaceutical company, and its therapeutic efficacy in the treatment of respiratory tract infections were evaluated. The minimum inhibitroy concentrations (MICs) of AZM, erythromycin (EM), clarithromycin (CAM) and roxithromycin (RXM) against 20 strains each of methicillin-susceptible Staphylococcus aureus (MSSA), methicillin-resistant S. aureus (MRSA), Escherichia coli, Klebsiella pneumoniae, Serratia marcescens and Pseudomonas aeruginosa, and 18 strains of Enterobacter cloacae were determined by the micro-broth dilution method using the Dynatech MIC 2000 system. As shown by the MICs obtained, AZM was less active against MSSA and MRSA, and more active against Enterobacteriaceae and P. aeruginosa than EM, CAM and RXM. Thirteen patients received a daily dose of 250 mg (6 cases) or 500mg (7 cases) of AZM per os for 3 days: 2 patients each with acute bronchitis and chronic bronchitis, 7 with acute pneumonia, 1 with Mycoplasma pneumoniae pneumonia and 1 with infection associated with old pulmonary tuberculosis. The clinical effects were excellent in 4 and good in 9 patients (efficacy rate: 100%). Eight strains were identified as causative organisms: 1 strain each of Haemophilus influenzae and S. aureus and 6 strains of Streptococcus pneumoniae. The 6 strains were eradicated but 1 strain each of S. aureus and S. pneumoniae persisted after therapy. Diarrhea occurred in 2 patients during AZM therapy and a transient elevation of serum transaminase was observed in another. These adverse reactions disappeared after completion of therapy. We conclude, from the above results, that AZM is one of the most useful oral antimicrobial agents and should be a drug of first choice in the treatment of respiratory infections.

    Original languageEnglish
    Pages (from-to)204-211
    Number of pages8
    JournalJapanese Journal of Chemotherapy
    Publication statusPublished - 1995 Jan 1


    • Azithromycin

    ASJC Scopus subject areas

    • Pharmacology
    • Pharmacology (medical)


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