Ceftaroline activity tested against viridans group streptococci from US hospitals

A total of 840 clinically relevant viridans group streptococci (VGS) isolates (1/patient episode) were collected from 71 US medical centers in 2013-2014. These organisms were tested for susceptibility by reference broth microdilution methods against ceftaroline and selected comparator agents. All isolates were speciated by matrix-assisted laser desorption ionization-time-of-flight (MALDI-TOF) mass spectrometry and were primarily from skin/soft tissue (32.6%) and bloodstream (32.3%) infections. Ceftaroline was highly active against all VGS species/groups with MIC50 and MIC90 values ranging from ≤0.015 to 0.03 μg/mL and ≤0.015 to 0.06 μg/mL, respectively. The highest ceftaroline MIC value was only 0.5 μg/mL (0.5% of strains) and ceftaroline (MIC50/90, 0.03/0.06 μg/mL) was 8-fold more active than ceftriaxone (MIC50/90, 0.25/0.5 μg/mL). The VGS groups most susceptible to ceftaroline were Streptococcus mutans and Streptococcus bovis (MIC90, ≤0.015 μg/mL), whereas the highest ceftaroline MIC values were observed among Streptococcus mitis and Streptococcus sanguinis groups. In summary, ceftaroline exhibited potent in vitro activity against VGS, including many uncommonly isolated species/groups for which very limited susceptibility information is currently available to guide therapy.