Macrolide resistance is also increasing, with the incidence of this much higher in Europe than in the US. Notable national and regional differences are illustrated, with highest macrolide resistance rates found in Spain, France and Italy. While not as high as in Europe, the incidence of macrolide resistance among Streptococcus pneumoniae is increasing in the United States. Results from a US study have recently been reported showing that from 1993 to 1999, low-level macrolide resistance increased from 10.6% in 1995 to 20.4% in 1999. M phenotype isolates (associated with moderate resistance) increased from 7.4% to 16.5%, and the median erythromycin MIC (minimum inhibitory concentration) of the M phenotype isolates increased from 4 to 8 mg/ml. Only for high-level resistance has a correlation with outcome been documented however.