Resistance Research Of Linezolid To Enterococcus

BackgroundLinezolid is a new important drug of the oxazolidinone. It has a better therapeutic effect to the infections caused by most gram-positive bacteria with its new structure and unique mechanism of action. In particular, it has a strong antibacterial effect to the special clinical gram-positive bacteria, including multi-drug resistant staphylococcus, vancomycin resistant enterococcus and so on. Since been approved to enter China in2007, it palys a huge role as antibacterial in the country’s major hospitals. It makes the problem that a lot of drug-resistant bacteria need clinical composite several antibiotics have been solved. At present, it has been approved for the treatment of a vairety of infectious diseases. The treatment effect for the enterococcus infection (especially the recurring vancomycin-resistance enterococcus infection) that have been gradually increased in recent years has made a figure. But with a lot of linezolid were used in clinical, the phenomenon of linezolid-resistance enterococcus isolated in clinical have appeared constantly.Objective To explore the condition of various types of antibiotic resistance of enterococcus isolated in clinical through the drug sensitive experiment of linezolid to the222strains of enterococcus isolated in clinical of overall and independent7strains enterococcus which had been done in our hospital from April2009to August2011. And to figure out the condition of linezolid-resistance and the minimal inhibitory concentration of linezolid of the corresponding strain independend, further understanding the drug-resistance condition of enterococcus for all types of antibiotics, especially for linezolid. At the same time, to analyse the gene sequence of the resistant strains of enterococcus and define the resistance formation mechanism in order to better guide the use of antimicrobial agents rationally in clinical.MethodsStrians had been isolated routinely and been biochemical identified and preserved by automatic instrument for bacte-ria identification of VITEK2compact. Agar dilution method and E-test paper diffusion method had been used to test the drug susceptibility of minimum inhibitory concentration(MIC) of enterococcus isolated in clinical and to measure its minimum antibacterial depth. The bacterial DNA had been extracted by genome extraction kit and boiling method. Multiplex PCR had been used to detect the DNA extracted from the3strians linezolid-resistance enterococcus and PCR products were identified by agarose gel electrophoresis and gene sequencing. The quality control strains were enterococcus faecalis ACTT27273, ATCC29212. WHONET5.4and SPSS11.0software were used to analyse and statistic the date.ResultsDuring the past3years, a total of222strains of enterococcus were isolated from a variety of clinical specimens, including113strains of enterococcus faecalis and103strains of enterococcus faecium. The majority of strains were isolated from sputum,urine,and secretion, accounting for31.5%,27.5%,13.5%, respectively. Among the various antibiotics commonly used in clinical, high concentration gentamicin exhibited the highest resistance to the isolates (70.7%), About65.8%,39.6%, and20.3%of enterococcus isolates were resistant to Cefaclor, Levofloxacin and ampicillin, respectively. Enterococci showed the lowest resistance rate to vancomycin and teicoplanin (1.8%and1.8%). Those vancomycin-resistant enterococci tested were enterococcus faecalis and enterococcus faecium,the former was1strain and the other was three. For the7strains of enterococci, the Minimum Inhibitory Concentration(MIC) was tested by AGAR dilution method and E-test paper diffusion method,the result of the former tested to strains-244,245,260,363,432,466,505were8,1,1,2,2,4,6ug/ml. The other were12,<0.16,<0.16,0.7,0.5,4,6ug/m.244,466,505showed resistant to Linezolid. DNA of the7strains detected by PCR, and PCR products were identified by agarose gel electrophoresis and gene sequencing which showed that244,466,505obtained the size of389bp product amplified. PCR products using DNAMAN software sequence alignment found:The quality control strains’2576nucleotide sequencing result for the guanine (G), present the single-peak as well as the three samples. The DNA sequence of the23s rRNA area of three samples referenced to the GeneBank showed that locus2576have not yet found any point mutations, but in locus2711, there was found A into T to strain466, after the repetition of sequencing of strain466found that there was a false positive.ConclusionVancomycin, teicoplanin and linezolid still possess the most potent antibacterial activity against Enterococcous faecium. However, vancomycin-resistant, linezolid-resistant Enterococcous have emerged. Different enterococci have different resistant spectrum. Rational selection and administration of antimicrobials against enterococcus faecium infection should be based on drug susceptibility test for better treatment and lowering the incidence of nosocomial infection. As reported, there has been a rising trend in linezolid, three strains linezolid-resistant had been found which showed a serious trend of linezolid resistant, may result by infection of enteroccus and the abuse of linezolid. The isolate showed that locus2576have not yet found any point mutations, contrasted to the area2332to2720bp of the sequence of the23s rRNA, there were no different between the three strains and the quilty control strain. After the repetition of sequencing of strain466found that there was a false positive. This result not as same as the fonner report which mentioned that there still other mechanisms of drug-resistance. This experiment and PCR product for23s r RNA V area2720-2332bp were shill limited, the other range the gene is variation unknown.already be so, whether there was other variation mechanism, it is not learned that, must also be further discussed.