Penicillin-susceptible and erythromycin-resistant Streptococcus pneumoniae in children with acute mastoiditis.

Resistance to erythromycin is usually associated with resistance to penicillin in Streptococcus pneumoniae isolates. Over the last few years, however, an increase has been detected in the number of Streptococcus pneumoniae isolates obtained from children with acute otitis media complicated by acute mastoiditis. These isolates are characterized by a penicillin-susceptible and erythromycin-resistant antibiotic profile. This observation prompted a review of the microbiology database and analysis of all Streptococcus pneumoniae isolates with this peculiar antibiotic profile at a university hospital in Madrid, Spain.