Macrolide Resistance Among Invasive Streptococcus pneumoniae Isolates

Authors:
  • KGKathryn Gay
    Kathryn Gay
  • DSDavid S. Stephens
    David S. Stephens
  • DVDuc J. Vugia
    Duc J. Vugia
  • MPMargaret Pass
    Margaret Pass
  • SJSusan Johnson
    Susan Johnson
  • NBNancy L. Barrett
    Nancy L. Barrett
  • WSWilliam Schaffner
    William Schaffner
  • PCPaul R. Cieslak
    Paul R. Cieslak
  • PMPeggy S. Maupin
    Peggy S. Maupin
  • EZElizabeth R. Zell
    Elizabeth R. Zell
  • JJJames H. Jorgensen
    James H. Jorgensen
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Abstract
Research from JAMA — Macrolide Resistance Among Invasive Streptococcus pneumoniae Isolates — ContextMacrolide antibiotics, including erythromycin, clarithromycin, and azithromycin, are the mainstays of empirical pneumonia therapy. Macrolide resistance among Streptococcus pneumoniae, the most common cause of community-acquired pneumonia, is increasing in the United States. Whether resistance is a significant problem or whether macrolides remain useful for treatment of most resistant strains is unknown.ObjectiveTo examine the epidemiology of macrolide-resistant pneumococci in the United States.Design and SettingAnalysis of 15 481 invasive isolates from 1995 to 1999 collected by the Centers for Disease Control and Prevention's Active Bacterial Core surveillance system in 8 states.Main Outcome MeasuresTrends in macrolide use (1993-1999) and resistance and factors associated with resistance, including examination of 2 subtypes, the M phenotype, associated with moderate minimum inhibitory concentrations (MICs), and the MLSB phenotype, associated with high MICs and clindamycin resistance.ResultsFrom 1993 to 1999, macrolide use increased 13%; macrolide use increased 320% among children younger than 5 years. Macrolide resistance increased from 10.6% in 1995 to 20.4% in 1999. M phenotype isolates increased from 7.4% to 16.5% (P<.001), while the proportion with the MLSB phenotype was stable (3%-4%). The median erythromycin MIC (MIC50) of M phenotype isolates increased from 4 µg/mL to 8 µg/mL. In 1999, M phenotype strains were more often from children than persons 5 years or older (25.2% vs 12.6%; P<.001) and from whites than blacks (19.3% vs 11.2%; P<.001).ConclusionsIn the setting of increasing macrolide use, pneumococcal resistance has become common. Most resistant strains have MICs in the range in which treatment failures have been reported. Further study and surveillance are critical to understanding the clinical implications of our findings.

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