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The purpose yearly analysis of Staphylococcus aureus to vancomycin MIC values ??changes, assess its vancomycin MIC drift trend understand VraSR two-component system in Staphylococcus aureus reduced susceptibility to vancomycin. Collected in 2007-2009 Chongqing and Guangzhou four clinical isolates of MRSA strains in the top three hospitals in Chongqing hospital A hospital, Guangzhou area, three hospitals for hospital B, C homes, D hospital. The broth microdilution Determination vancomycin MIC calculate MIC50, MIC90, MIC values ??geometric mean sensitive rates and resistance rates to analyze the trend of the MIC. Then, MRSA strains PCR detection vraSR gene sequencing analysis, and through the genebank's Blast with N315 genome analysis, the gene for amino acid mutations. In addition, in vitro induced by low doses of vancomycin MRSA clinical strains, MIC values ??phase after the parent strain and induced the strains detected vraSR gene, to analyze whether the amino acid mutations, line RT-PCR the detection vraSR gene expression levels change. Results from 2007 to 2009, the clinical isolates of MRSA strain 779, including 264 in 2007, 342 in 2008, 173 in 2009. Research in general is the geometric mean of the vancomycin MIC 0.911,0.954,0.976 μg / ml, showed an increasing trend (P lt; 0.001) in the various hospitals, hospital A MIC geometric mean of and for 1.052,1.06,1.069 μg / ml, showed an increasing trend (P lt; 0.001). B hospital MIC geometric mean for 0.885,0.901,1.006 μg / ml, showed an increasing trend (P lt; 0.001). C hospital MIC geometric mean 0.915,0.954,0.926 μg / ml, increased year by year trend (P gt; 0.05). D hospital MIC geometric mean 1.025,1.001,0.865 μg / ml, increased year by year trend (P gt; 0.05). MRSA strains were detected bicomponent the system vraSR gene. A the MIC = 2μg/mL MRSA strains vraR of 59 glutamic acid was mutated to aspartic acid. 10 MRSA induced by vancomycin in vitro experiments, four days after five strains MIC values ??is 0.75μg/ml rise as 2μg/ml 6 days after a strains MIC values ??from 2μg/ml rise as the 4μg/ml 12 days The the the Zhu Zhu strains MIC values ??rose from 2μg/ml for the 4μg/ml 1 strains MIC values ??remained 2μg/ml remaining five MIC values ??remained at 0.75 μg. The different stages of strain after induction vraSR gene mutation not found, vraR gene expression level with the MIC values ??rise. The conclusion overall MRSA strains vancomycin MIC drift trend exists. Hospital A and hospital B visible the drift trend, no drift trend of hospital C and D homes. All MRSA strains were detected the bicomponent the system vraSR gene found the one case vraR gene mutation. In vitro induction of vancomycin, MRSA vancomycin MIC by 0.75μg/ml reached 4μg/ml, simultaneously the strains of vraR expression amount raised with MIC values ??increase, but did not find vraSR gene mutation.
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