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 cMLSB and 1/19 iMLSB 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 cMLSB phenotype, and 4 and <0.008 mg/l for the iMLSB phenotype. This is the first report studying the prevalence of macrolide resistance determinants in S. pneumoniae in our country.