Molecular characterisation of Hungarian macrolide-resistant Streptococcus pneumoniae isolates, including three highly resistant strains with the mef gene

The macrolide resistance of 304 Hungarian Streptococcus pneumoniae isolates was investigated. Antibiotic sensitivity testing was performed in air and in 5% CO2. More erythromycin resistance was noted when growth was in CO2. A resistance determinant was found in almost all isolates: erm(B) gene (87.4%), mef genes (9.2%) and one strain with the erm(TR) gene. This indicates that screening for carriage of resistance determinants should always be done in the presence of 5% CO2. We found three isolates with mef(E), which were highly resistant to erythromycin. These contained multiple and some novel, ribosomal mutations. The most prevalent serogroups were 6, 19 and 14. Based on the PFGE pattern, we found identity between the Hungarian isolates and two PMEN clones.