Phenotypic and genotypic characterization of macrolide resistant Streptococcus pneumoniae recovered from adult patients with community-acquired pneumonia in an Argentinian teaching hospital.

Streptococcus pneumoniae isolates (n = 262) were recovered from adult patients with community-acquired pneumonia. Erythromycin-resistance levels increased from 9% (1997-1998) to 16% (2000-2002). Sampling for resistance mechanisms prevalent within 19 erythromycin-resistant S. pneumoniae showed mef(E) in 13/19 isolates while 4/19 carried the erm(B) gene (3/19 cMLS(B) and 1/19 iMLS(B) phenotype). MIC ranges for erythromycin and clindamycin were 0.5-16 mg/l and <0.008-0.063 mg/l for the M phenotype, 128-512 mg/l and 128-256 mg/l for the cMLS(B) phenotype, and 4 and <0.008 mg/l for the iMLS(B) phenotype. This is the first report studying the prevalence of macrolide resistance determinants in S. pneumoniae in our country.