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A Preliminary Study on the Interactions of Three-Drug Combinations at Sub-Lethal Dosages in Treating Antibiotic Resistant Staphylococcus epidermidis


Currently, approximately 700,000 people die each year from antibiotic resistant infections. This number could reach 10 million by 2050 if a solution is not found. A better understanding of the interactions that exist between antibiotics could offer a solution to this major public health problem. Interactions can be either synergistic, antagonistic or additive. This preliminary study sought to investigate susceptibility of S. epidermidis to specific three-drug combinations when S. epidermidis had evolved resistance to one of the drugs in the combinations. All drug combinations contained sub-lethal concentrations of piperacillin, tetracycline and either chloramphenicol, doxycycline, erythromycin or neomycin. Results could not be accurately obtained due to aggregation of the cells in the microtiter plates. However, the experiment suggested S. epidermidis was susceptible to the three-drug combinations even when it evolved resistance to chloramphenicol or erythromycin and was less susceptible to the three-drug combination when it evolved resistance to doxycycline or neomycin. The aggregation issue has since been addressed and new data will be collected using deep-well 96-well microtiter plates.

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