The Study On Resistance Mechanism Of Enterococci By Linezolid In Vitro

ObjectiveOver the past 10 years, nosocomial infections caused by the enterococcus was paid more and more attention, and the U.S. hospital infection surveillance system has listed it as the second largest pathogen of nosocomial infection, accounting for 12% of causes of hospital infection. In China, enterococcal infections also have significantly increasing trend.18% to 50% of Enterococci causing nosocomial infection was resistant to vancomycin, the vancomycin-resistant enterococci are resistant to multiple antimicrobial drugs, which brought enormous difficulties to clinical treatment.Linezolid is a new oxazolidinone antibiotic, and is considered as the only treatment medicines of VRE infections and hospital infection control outbreak of VRE. However, with the large-scale public use of the drug in clinical work, there is the reports about linezolid-resistant strains. Therefore, the study of resistance to linezolid resistant enterococci has great significance in clinical medicine. In this study, begin with the induction of linezolid resistant to enterococci, let enterococci in vitro long-term exposure to low dose linezolid, and then gradually increase the concentration of linezolid, observe the growth of enterococci, judge whether Enterococcus of secondary resistance to linezolid easy or not. Through compare the sensitive and resistant enterococci Enterococcus 23s rRNA gene change, and explore mechanism of enterococci resistance to linezolid. The study to arouse the broad masses of medical attention, rational use of drugs to reduce the incidence of drug resistance.MethodsFirstly, identify and culture 9 clinical isolated enterococci and a quality control strains, and then use the standard recommended by the 2009 CLSI agar dilution sensitivity test, get the MIC value of 10 strains of enterococci to linezolid. Next,induction of multi-drug resistance test. Test the MIC values of drug-resistant strains of by agar dilution method, compare the drug resistance before and after induction. Then give 23s rRNA gene of Enterococcus again V region 2332bp-2720bp fragment of PCR amplification, if there is the gene mutation exists in G2576U will be Mael restriction enzyme cut into two, otherwise not. Apply the enzyme digestion, electrophoresis method to separate the wild gene mutation, and then analysis results by Tanon Gis (days to) gel image, and then get the mutant number of G2576U in resistant contained.ResultsAfter the nine clinical isolates of enterococci and quality control strains the induction of resistance in vitro, the MIC values were significantly increased, respectively, an increase of 8 to 64 times, and is proved to be stable by the stability of the experimental drug-resistant strains.In this study, the stability of induced resistant strains were detected G2576U mutation, and MIC values of enterococci increased while the number of mutations G2576U increased. This is consistent with the study of Prystowsky, J.,which shows that enterococci resistant to linezolid related to the 2576 of the gene mutation,the drug-resistant of enterococci has positive correlation with the number of mutations G2576U.ConclusionIinezolid could induce acquired drug resistance of enterococcus and its resistance mechanism relates to the mutations of 23s rRNA gene point of enterococci.