FIG 1.

Macrolide resistance in M. pneumoniae specimens in the United States, 2006 to 2013. (A) Proportions of macrolide-resistant and sensitive M. pneumoniae strains identified in individual outbreaks. The proportions of sensitive and resistant strains in all outbreak specimens (n = 156), sporadic cases and clusters (n = 20), and all specimens (n = 176) are also shown. Macrolide susceptibility could not be determined for 23 (12%) of 199 specimens due to the lack of an available specimen or inadequate amplification of the target region. (B) Proportion of macrolide-resistant M. pneumoniae infections identified over the study period. Nineteen resistant strains (10%) were identified during this time period. The number of M. pneumoniae-positive specimens with macrolide susceptibility results is shown for each year; no positive specimens were available from 2008 or 2010.