Study Of The Pathogenic Enhancement Mechanism Of Enterococcus Faecium

BackgroundEnterococci are Gram-positive bacteria, normal inhabitants of the alimentary tract of humans and animals. Enterococcus faecium generally is considered to be a species with little virulence, because it was found to be responsible for only 10% of enterococcal infections on human. However, in the past decade, the relative percentage of enterococcal infections attributed to E. faecium has greatly increased, in some instances to 30%~40% of enterococcal infections. Vancomycin resistant enterococci, most of which are E. faecium, are now responsible for 25% of enterococcal infections that occur in ICU in the United States. These data suggest that some E. faecium strains may be accumulating determinants that increase their virulence. However, the mechanisms of pathogenesis and virulence factors of E. faecium are not yet well understood, and increasing multidrug resistance in enterococci has made it more difficult to treat with enterococcal infections. How to cure E. faecium infection is always the focus of research in the infection disease domain. Hyaluronidase (Hyl), enterococcal surface protein (Esp) and enterococcus faecium antigen (EfaAfm) were found to be the main potential virulence factors which were probably correlated with the pathogenicity of E. faecium.ObjectTo investigate the pathogenic mechanism of Enterococcus faecium and the relationship between its potential virulence factors and pathogenicity through the virulence and antimicrobial resistance study in clinical Enterococcus faecium from a tertiary teaching hospital in Chongqing from 2006.1 to 2009.6, and provide a rational usage of antibiotics to treat the infection caused by Enterococcus faecium.MethodsA Multiplex PCR was applied for the detection of hyaluronidase (Hyl), enterococcal surface protein (Esp) and enterococcus faecium antigen (EfaAfm) genes. Hyaluronidase detection of Strepotocccus pneumoniae was used to screen the Hyl (+) of Enterrcoccus faecium. Minimal inhibitory concentration(MIC) was employed to evaluate the antimicrobial resistance. Data were summarized and analyzed by WHONET 5.4 and SPSS 11.0 softwares.ResultsThe detection rate of EfaAfm, Esp and Hyl genes from clinical Enterococcus faecium were 98.6%,59.7% and 16.7%, respectively. No isolates produced Hyaluronidase for using hyaluronidase detection of Strepotocccus pneumoniae in Hyl gene-posotive of clinical Enterococcus faecium. Among the commonly clinical-used antibiotics, cefaclor exhibited the highest resistance to the isolates (100%). About 94.4%, 90.3%, and 83.3% of enterococcus faecium isolates were resistant to levofloxacin, ampicillin and high-dose gentamicin, respectively. During the past 4 years,a total of 314 strains of enterococci were isolated from a variety of clinical specimens, including 159 strains of enterococcus faecalis and 131 strains of enterococcus faecium. The majority of strains were isolated from urine, sputum, and secretion, accounting for 31.5%, 28.3%, 16.0%, respectively. Among the various antibiotics commonly used in clinical, erythromycin exhibited the highest resistance to the isolates (89.2%), About 65.9%, 59.6%, and 24.2% of enterococcus isolates were resistant to ciprofloxacin, ampicillin and nitrofurantoin, respectively. Enterococci showed the 1owest resistance rate to vancomycin and teicoplanin (2.0% and 0.3%). Those vancomycin-resistant enterococci tested were enterococcus faecalis and enterococcus gallinarum.ConclusionThe results of the detection rates of Hyl, Esp and EfaAfm gene, the potential virulence of Enterococcus Faecium, are in consistent with the previous studies. Hyl and Esp gene show an ascending tendency in these years while EfaAfm doesn't. This proves the pathogenic enhancement mechanism of Enterococcus faecium is probably related with the acquisition of virulence factors. This Study shows that the increasing infection caused by enterococcus faecium probably is due to they acquired more virulence factors in China, and disseminated in hospitals. Clinician should pay attention to the personal and medical instrument sanitation, taking good self-protection to prevent nosocomial dissemination. Vancomycin, teicoplanin and linezolid still possess the most potent antibacterial activity against Enterococcous faecium. However, vancomycin-intermediate Enterococcous faecium 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.