DNA Banding Pattern Polymorphism in Vancomycin-Resistant Enterococcus faecium and Criteria for Defining Strains

Abstract

The degree of DNA banding pattern polymorphism exhibited by vancomycin-resistant Enterococcus faecium (VREM) strains isolated on a renal unit over an 11-month period was investigated. Thirty VREM strains from different patients were analyzed by pulsed-field gel electrophoresis (PFGE; with extended run and optimal pulse times), ribotyping, plasmid profile analysis, biotyping, pyrolysis mass spectrometry, and antibiogram analysis. PFGE resolved 17 banding patterns which formed four distinct clusters at the 82% similarity level. Intercluster band differences ranged from 14 to 31 bands. The strains in one cluster, which contained seven patterns that differed from each other by one to seven bands and from the common pattern by five bands, were confirmed to be a single strain by four of the five other typing methods. The strains in a second cluster with eight patterns, which differed from each other by 1 to 12 bands, contained two subclusters. This subdivision was supported by ribotyping and biotyping. However, it was unclear whether these subclusters represented distinct strains. In one strain, marked polymorphism (patterns that differed from each other by up to four bands) was observed in the ribotype pattern. This study demonstrates the high degree of DNA banding pattern polymorphism found for some strains of VREM and illustrates the complexity involved in defining such strains.

Evaluation of clonality in enterococci isolated in Brazil carrying Tn1546-like elements associated with vanA plasmids

“…We have analysed the PFGE profiles according to the generally accepted criteria proposed by Tenover et al (1995), although they were established for analyses of discrete sets of isolates obtained during epidemiologic studies of potential outbreaks in hospitals or communities spanning relatively short periods (1-3 months). The PFGE profiles were also analysed by criteria proposed by Morrison et al (1999), which consider that single vancomycin-resistant E. faecium strains may differ from each other by seven bands in the PFGE typing. The clonality of isolates proposed by both criteria showed the same results, because VRE strains classified as having PFGE profiles B and C showed nine and 11 different bands in relation to pulse-field type A.…”

Molecular epidemiology of Streptococcus bovis causing endocarditis and bacteraemia in Italian patients

“…Preparation of chromosomal DNA for PFGE was as described previously [13], with minor modifications. Briefly, cell suspensions (c. 2 · 10 9 CFU) were mixed at 50°C with an equal volume of low-melting-point agarose 2% w ⁄ v and dispensed as 20-lL disks that were allowed to solidify at 4°C.…”

Safety Evaluation and Antibacterial Activity of Enterococci Isolated from Lighvan Cheese

“…Therefore, the genus has not been yet considered as "generally recognized as safe" (GRAS) (Nallapareddy et al 2008). Enterococci have been implicated in the cause of nosocomial infections, bacteremia, endocarditis and infections of urinary tract with E. faecalis and E. faecium being the most common (Morrison et al 1999;Kuzucu et al 2005). Antibiotic resistance along with possessing multiple virulence factors such as resistance to host defense mechanisms and colonizing the host gastrointestinal tract, overgrowth and translocation result in enterococcal infections.…”