In vitro antagonistic inhibitory effects of palm seed crude oils and their main constituent, lauric acid, with oxacillin in Staphylococcus aureus.

Infections caused by Staphylococcus aureus are a serious global threat, and with the emergence of antibiotic resistance, even more difficult to treat. One of the possible complications in antistaphylococcal therapy represents negative interactions of antibiotics with food. In this study, the in vitro interaction between oxacillin and crude palm seed oil from Astrocaryum vulgare, Cocos nucifera, and Elaeis guineensis against nine strains of S. aureus was determined using the checkerboard method. Lauric acid was identified as a major constituent of all tested oils by gas chromatography. The results showed strong concentration dependent antagonistic interactions between palm oils and oxacillin with values of fractional inhibitory concentrations indices ranging from 4.02 to 8.56 at concentrations equal or higher than 1024 µg/mL of the tested oils. Similarly, lauric acid in combination with oxacillin produced antagonistic action with fractional inhibitory concentration indices ranging from 4.01 to 4.28 at 1024 µg/mL. These findings suggest that interference between oxacillin and palm oils and their constituents can negatively affect the treatment of staphylococcal infections in humans and other animals.

Inhibitors of reactive oxygen species accumulation delay and/or reduce the lethality of several antistaphylococcal agents.

Perturbation of hydroxyl radical accumulation by subinhibitory concentrations of 2,2'-bipyridyl plus thiourea protects Escherichia coli from being killed by 3 lethal antimicrobial classes. Here, we show that 2,2'-bipyridyl plus thiourea delays and/or reduces antimicrobial killing of Staphylococcus aureus by daptomycin, moxifloxacin, and oxacillin. While the protective effect of 2,2'-bipyridyl plus thiourea varied among strains and compounds, the data support the hypothesis that hydroxyl radical enhances antimicrobial lethality.

In vitro evaluation of clindamycin in combination with oxacillin, rifampin, or vancomycin against Staphylococcus aureus.

In a study of antibiotic combinations of clindamycin with rifampin, oxacillin, or vancomycin using the time kill-curve method, the combination of clindamycin and rifampin were sometimes synergistic (5 of 15 times), otherwise indifferent and always enhanced killing of fifteen tested Staphylococcus aureus isolates. In contrast, vancomycin and clindamycin or oxacillin and clindamycin were either indifferent or antagonistic (approximately 50%). Vancomycin alone, however, was generally as effective as the combinations of clindamycin and rifampin.

Antagonism between nafcillin or oxacillin and rifampin against Staphylococcus aureus.

By the time-kill method, the combinations of nafcillin plus rifampin and oxacillin plus rifampin were antagonistic against 20 strains of Staphylococcus aureus. No synergism was demonstrated.