Increase in pneumococcus macrolide resistance, United States.

During year 6 (2005-2006) of the Prospective Resistant Organism Tracking and Epidemiology for the Ketolide Telithromycin surveillance study, 6,747 Streptococcus pneumoniae isolates were collected at 119 centers. The susceptibility of these isolates to macrolides was compared with data from previous years. Macrolide resistance increased significantly in year 6 (35.3%) from the stable rate of approximately 30% for the previous 3 years (p<0.0001). Macrolide resistance increased in all regions of the United States and for all patient age groups. Rates were highest in the south and for children 0-2 years of age. Lower-level efflux [mef(A)]-mediated macrolide resistance decreased in prevalence to approximately 50%, and highly resistant [erm(B) + mef(A)] strains increased to 25%. Telithromycin and levofloxacin susceptibility rates were >99% and >98%, respectively, irrespective of genotype. Pneumococcal macrolide resistance in the United States showed its first significant increase since 2000. High-level macrolide resistance is also increasing.