Analysis of In Vitro Antibacterial Activity of Combined-Use of Drugs Against Methicillin Resistant Staphylococcus Aureus in Respiratory Tract Infection

Objective. To investigate the in vitro antibacterial activity of routine antibiotics on respiratory tract infections with methicillin resistant Staphylococcus aureus (MRSA) and to provide laboratory reference for the clinical treatment of MRSA respiratory tract infections. Methods. Bacteria were cultured and isolated by routine method and identified by staphylococcus aureus latex kit and VITEK II bacteria analyzer. MRSA were identified by latex coagulation method. The in vitro antibacterial activity of antibiotic was tested by microdilution method and was analyzed according to CLSI standards. Results. 75 strains of MRSA were isolated from respiratory tract samples. The highest isolated ratio was from the departments of neurosurgery, respiratory and neurology, with 30.7%, 20.0%, and 18.7% respectively. All of the 75 strains were sensitive to Linezolid (LZD), Vancomycin (VAN) and Teicoplanin (TEC). The resistant rates of Levofloxacin (LVX) and Rifampicin (RIF) were 97.3% and 78.3% respectively. The FIC < 1 of RIF combining LZD, VAN and TEC was 25.3%-68.0%. The FIC < 1 of LVX combining LZD, VAN and TEC was 8.0%-36.0%. The difference among the combined drugs in each group had statistical significance (P <0.01). Conclusions. The LZD, VAN and TEC, which were the best choices to treat MRSA infection, had better antibacterial activity against MRSA. Mono-antibiotic or combined-use of two species of drugs should be selected according to individual infectious cases in clinic. © 2013 American Scientific Publishers All rights reserved.