Cost-Effective Algorithm for Detection and Identification of Vancomycin-Resistant Enterococci in Surveillance Cultures

Abstract

A study was undertaken to develop an easy-to-use and cost-effective algorithm for the detection and identification of vancomycin-resistant enterococci (VRE) in surveillance cultures, because the incidence of VRE outbreaks in institutions across Canada has made continuous surveillance a necessity. Enterococcus faecium and Enterococcus faecalis carry transferable resistance genes and hence are a problem for infection control. In laboratory surveillance, however, Enterococcus gallinarum and Enterococcus casseliflavus, which exhibit low-level nontransferable resistance, are also encountered and often create confusion in identification. Included in this study were a total of 218 strains of enterococci and other streptococci isolated from surveillance cultures. Conventional methods were used to determine their biochemical activities, and speciation was attempted in 121 strains using a rapid multiplex polymerase chain reaction (PCR) method that utilized primers for the vanA, B, C1, C2/C3 and ddl genes. The results indicated that by using only a few tests (Gram stain, pyrrolidonyl arylamidase activity, motility, xylose and methyl-alpha-D-glucopyranoside utilization), Enterococcus faecium/faecalis strains could be accurately differentiated from Enterococcus gallinarum/casseliflavus strains. For the 121 strains on which PCR was performed, there was a 100% correlation with the biochemical identification, with the added advantage that the presence of van genes could be determined at the same time. The cost of identification using minimal biochemical testing and PCR was less than that of identification using automated systems or a battery of conventional biochemical methods. The algorithm presented here may be used in the microbiology laboratory.

Evaluation of the EVIGENE VRE Detection kit for detection of vanA and vanB genes in vancomycin-resistant enterococci

“…Nevertheless, the total time required for PCR analysis, including sample preparation and gel electrophoresis, is about 3 . 5 h (Kanchana et al, 2000). The EVIGENE VRE Detection kit does not contain hazardous chemicals and is easy to evaluate.…”

Prevalence and Molecular Epidemiology of Vancomycin-Resistant Enterococci (VRE) Strains Isolated from Animals and Humans in Korea

“…infection including VRE has been known mainly as a hospital-acquired infection occurring in groups through sporadic infection or the transmission of clonal bacterial strains. Different from the US, there have been reports in many European countries, such as England, Belgium, and the Netherlands, that although VRE isolation rate is low, VRE is being colonized in the intestinal tract through livestock or pets in the community4, 11, 16). Based on the fact that most of the nosocomial VRE bacterial strains have different genetic heterogeneities from one another, it was first thought in Europe that VRE might have entered from the community, and it has been verified by many reports that genetically associated VRE bacterial strains have been isolated from livestock on farms, raw meats, and healthy individuals9, 10).…”

“…Thus, there is no effective therapeutic agent, and it is perceived to be a very serious pathogenic bacterium because vancomycin-resistant Staphylococcus aureus (VRSA) can emerge through the transferring of vancomycin-resistant genes to S. aureus . In Japan, VRSA with higher than 8 µg/mL of MIC to vancomycin was actually isolated from a patient for the first time in 199616). Afterwards, it was also found in the US, France, and domestically, and this issue is being raised as a serious problem.…”

“…infection until recently, were reported in France for the first time in 19863). Since then, vancomycin-resistant enterococci (VRE) have continuously been on increasing trends in Europe and North America, and it was isolated domestically for the first time in 1992, showing a rapidly increasing trend centering around large hospitals since 199816, 18). The vancomycin resistance genotypes reported thus far include: vanA , vanB , vanC , vanD , vanE , and vanG , most of which are vanA and vanB types.…”

Routine Molecular Identification of Enterococci by Gene-Specific PCR and 16S Ribosomal DNA Sequencing

“…It has been succesfully used to identify vancomycin-resistant enterococci (8,13,18,21,22,25,26,30,31), but it may also be used broadly to identify all enterococci; nevertheless, this approach certainly fails to identify some enterococcal species outside the reach of the primers, and for this reason it is also necessary to include among the proposed molecular methods for enterococcal species identification the amplification and sequencing of the 16S ribosomal DNA (rDNA) gene (25,28,38). Two hundred seventy-nine clinical strains consecutively identified as enterococci by three hospital laboratories in Rome were studied ( Table 1 All strains submitted as glycopeptide resistant were verified with the E-test method (AB BIODISK, Solna, Sweden) in our laboratory.…”