methicittin-resistant Staphylococcus aureus: an experimental study

Introduction: The treatment of postoperative mediastinitis is very important because of its high morbidity, mortality, and increased hospital stay and hospital costs. The aims of our research were to investigate whether linezolid alone can be an effective treatment agent for methicillin-resistant Staphylococcus aureus (MRSA) mediastinitis, and to determine whether linezolid can provide synergistic activity when given in combination with rifampin.Methods: A partial upper median sternotomy was performed on 70 rats. The animals were divided into seven groups: an uncontaminated control group; an untreated contaminated group; three contaminated groups that received antibiotic therapy with either 25 or 50 mg/kg linezolid twice a day, or rifampin 5 mg/kg twice a day; and two contaminated groups that received a combination therapy consisting of 25 or 50 mg/kg linezolid and rifampin 5 mg/kg twice a day. The antibiotic treatment tasted 7 days. Tissue samples from the upper ends of the sternum and swab specimens of the upper mediastinum were obtained and evaluated microbiotogically.Results: The 25-mg/kg dose of linezotid, either atone or combined with rifampin, was not effective in reducing the bacterial. counts in mediastinum and sternum. Quantitative bacterial cultures of mediastinum and sternum were significantly lower in the groups receiving 50 mg/kg linezolid alone or in combination with rifampin compared with the control. Adding of rifampin to linezotid therapy did not result in a significant change in bacterial. counts versus linezotid atone.Conclusion: A high dose of linezotid should be considered as a possible therapeutic agent for the treatment of post-sternotomy infection caused by MRSA. (c) 2007 International Society for Infectious Diseases. Published by Elsevier Ltd. All rights reserved