Patterns of macrolide resistance determinants among community-acquired Streptococcus pneumoniae isolates over a 5-year period of decreased macrolide susceptibility rates

Erythromycin resistance rates were found to be increased, from 7.1 in 1993 to 32.8% in 1997, among community-acquired Streptococcus pneumoniae isolates from the Siena area of central Italy. Most of the erythromycin-resistant isolates carried ermAM determinants and were also resistant to josamycin and clindamycin, whereas a minority (5.8%) carried mefA determinants and remained susceptible to the latter drugs.