Activity of ceftaroline and comparator agents tested against Staphylococcus aureus from patients with bloodstream infections in US medical centres (2009-13)

Abstract

Objectives: The objective of this study was to evaluate the in vitro antimicrobial activity of ceftaroline and comparator agents tested against Staphylococcus aureus isolates causing bloodstream infection (BSI).

Methods: A total of 4426 S. aureus isolates from patients with BSI were collected in 150 medical centres in the USA in 2009-13 and tested for susceptibility to ceftaroline and comparators by the CLSI broth microdilution method.

Results: Overall, 45.5% of isolates were MRSA. Ceftaroline (MIC50/90, 0.25/1 mg/L) was active against 97.9% of S. aureus isolates at ≤1 mg/L (highest MIC, 2 mg/L). Daptomycin (MIC50/90, 0.25/0.5 mg/L), linezolid (MIC50/90, 1/2 mg/L) and vancomycin (MIC50/90, 1/1 mg/L) were active against ≥99.8% of isolates at the respective susceptible breakpoints. Susceptibility rates for clindamycin (MIC50/90, ≤0.25/>2 mg/L) and levofloxacin (MIC50/90, ≤0.5/>4 mg/L) were 80.8% and 59.2%, respectively. Against MSSA, ceftaroline (MIC50/90, 0.25/0.25 mg/L; 100.0% susceptible) was 16-, 4-8- and 4-fold more active in vitro (based on MIC50/90) than ceftriaxone (MIC50/90, 4/4 mg/L), linezolid (MIC50/90, 1/2 mg/L) and vancomycin (MIC50/90, 1/1 mg/L), respectively, and slightly more potent than daptomycin (MIC50/90, 0.25/0.5 mg/L). When tested against MRSA, ceftaroline was active against 95.4% and 100.0% of isolates at ≤1 and ≤2 mg/L, respectively. Moreover, ceftaroline retained significant activity against S. aureus with reduced susceptibility to vancomycin, daptomycin, clindamycin, levofloxacin and trimethoprim/sulfamethoxazole.

Conclusions: Ceftaroline demonstrated potent in vitro activity when tested against a large collection of contemporary (2009-13) S. aureus isolates causing BSI in US hospitals.

Keywords: MRSA; antimicrobial resistance; bacteraemia; surveillance.