Detection of Synergistic Antimicrobial Activities of Ceftaroline, Telavancin, Daptomycin, and Vancomycin Against Methicillin-Resistant Staphylococcus aureus Strains in Intensive Care Units

Methicillin-resistant Staphylococcus aureus (MRSA) is a leading pathogen of serious infectious diseases in intensive care units. Novel antibiotic combination therapies are needed to treat serious infectious diseases caused by MRSA. Our objective was to evaluate the minimum inhibitory concentrations (MICs) of ceftaroline (CPT), telavancin (TLV), daptomycin (DPC), and vancomycin (VA) alone and in vitro synergistic activity of CPT-TLV, CPT-DPC, and CPT-VA combinations against MRSA isolates. Fifty MRSA strains isolated from blood (90%) and tracheal aspirate (10%) of patients in intensive care units (ICUs) between 2013 and 2016 were included in the study. The Epsilometer test was used for determining the synergistic activities of antibiotic combinations. We evaluated the synergistic, additive, indifferent, and antagonist effects of MRSA strains by the fractional inhibitory concentration (FIC) index. Of the 50 MRSA strains tested, 100% were susceptible to TLV, DPC, and VA. CPT was detected as resistant in 3 (6%) of the isolates. CPT-TLV, CPT-DPC, and CPT-VA combinations were found to have synergistic effects in 14%, 38%, 10% and additive effects in 40%, 32%, and 22% of the isolates, respectively. No antagonism was detected in any of the combinations. The combination of CPT with DPC showed the best synergy profile among all antibiotic combinations tested against MRSA isolates obtained from patients in ICUs.