Decreased ceftriaxone susceptibility in emerging (35B, 6C) and persisting (19A) Streptococcus pneumoniae serotypes in the USA (2011 — 2012): Ceftaroline remains active in vitro among β-lactam agents

ABSTRACT

A total of 8.7% (103/1,190) and 21.0% (249/1,190) Streptococcus pneumoniae collected in the USA during the 2011-2012 AWARE Surveillance Program were ceftriaxone non-susceptible according to CLSI (≤1 μg/ml for susceptible) and EUCAST (≤0.5 μg/ml for susceptible) criteria, respectively. Decreased susceptibility to ceftriaxone (MIC, ≥1 μg/ml) was frequently observed among serotypes 19A (51.4%; 128/249) and 35B (29.7%; 74/249), which were most often observed in the East South Central and South Atlantic regions. Ceftaroline (MIC_50/90, 0.12/0.25 μg/ml) remained active (≥96.8% susceptible) when tested against these less susceptible isolates.