Study of vancomycin MIC variance in methicillin-resistant Staphylococcus aureus from lower respiratory tract

OBJECTIVE To study the vancomycin MIC variance in methicillin-resistant Staphylococcus aureus(MRSA) from lower respiratory tract from 2003 to 2006 in The Third Affiliated Hospital of Sun Yat-sen University. METHODS MIC of vancomycin in MRSA was determined by agar dilution method.The data of the vancomycin MIC variance was analyzed by SPSS 10.0. RESULTS The number of MRSA isolated were 24 in 2003 and 139 in 2006.The MIC value to vancomycin of MRSA from 2003 to 2006 did not shift.The percentage of MRSA isolates with a vancomycin MIC of 1.0 μg/ml(62.5%-85.0%) was significantly higher than that of 0.5 μg/ml(15.0%-37.5%). CONCLUSION The high percentage of strains with vancomycin MIC in the 1 μg/ml may be the reason of vancomycin treatment failure.