Teicoplanin combined with various antibiotics and human blood against a multiple-drug-resistant strain of Staphylococcus aureus.

Neither teicoplanin nor vancomycin at 2, 1 and 0.5 micrograms/ml consistently killed inocula of representative isolates of a multiple-drug-resistant (MDR) strain of Staphylococcus aureus in the presence of 65% (v/v) of fresh, defibrinated human blood, although both antibiotics sterilized tube contents in Mueller-Hinton broth (MHB). With added human blood, teicoplanin (1 microgram/ml) combined with rifampin (1 microgram/ml) was the most effective in vitro combination, followed by teicoplanin (1 microgram/ml) + amoxicillin (8 micrograms/ml) + clavulanate (3 micrograms/ml), ampicillin (8 micrograms/ml) + sulbactam (8 micrograms/ml), cefamandole (8 micrograms/ml), fosfomycin (4 micrograms/ml + 25 micrograms/ml glucose-6-phosphate), imipenem (8 micrograms/ml), netilmicin (4 micrograms/ml), trimethoprim + sulfamethoxazole (1/19 micrograms/ml) and vancomycin (1 microgram/ml), respectively. Conversely, teicoplanin (1 microgram/ml) combined with fusidic acid (0.5 micrograms/ml) and ofloxacin (4 micrograms/ml), respectively, proved ineffective with 65% (v/v) added human blood. In concurrent control tubes, however, all drug combinations were bactericidally active in MHB against the MDR strain of S. aureus.