Loss of vancomycin resistance not completely dependent on the Tn1546 element in Enterococcus faecium isolates

Choi, Hyun Jin; Nam, Daesil; Peck, Kyong Ran; Song, Jae-Hoon; Shin, Dongwoo; Ko, Kwan Soo

doi:10.1016/j.diagmicrobio.2010.08.030

Cited by 15 publications

(10 citation statements)

References 15 publications

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“…Deletions in either or both of the vanR and vanS genes have been shown to result in vancomycin susceptibility (36,37). We did not detect the vanS gene in the BC169 isolate but detected vanS in a known vancomycin-resistant, vanA-positive strain (ATCC 51559) (data not shown).…”

Section: Resultsmentioning

confidence: 70%

Evaluation of Three Rapid Diagnostic Methods for Direct Identification of Microorganisms in Positive Blood Cultures

et al. 2014

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Section: Resultsmentioning

confidence: 70%

Evaluation of Three Rapid Diagnostic Methods for Direct Identification of Microorganisms in Positive Blood Cultures

et al. 2014

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“…In the absence of vanR and vanS genes, these isolates may not express vanH, vanA, or vanX and may remain vancomycin susceptible. However, in a previous study, a partial deletion of vanS in two E. faecium isolates resulted in one isolate being susceptible to vancomycin, whereas the other was resistant to vancomycin (21). Therefore, expression of vancomycin resistance may not be completely dependent on the presence of functional vanR and vanS genes.…”

Section: Discussionmentioning

confidence: 99%

Outbreak of Vancomycin-Susceptible Enterococcus faecium Containing the Wild-Type vanA Gene

Szakacs¹,

Kalan

McConnell³

et al. 2014

J Clin Microbiol

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e Accurate detection of vancomycin-resistant enterococci (VRE) is essential in preventing transmission in health care settings. Chromogenic media are widely used for screening VRE because of fast turnaround times (TAT) and high sensitivity. We report an outbreak of Enterococcus faecium bearing vanA yet susceptible to vancomycin (vancomycin-variable Enterococcus [VVE]). Between October 2009 to March 2011, clinical and screening specimens (n ‫؍‬ 14,747) were screened for VRE using VRE-selective medium and/or PCR. VVE isolates were genotyped to determine relatedness. Plasmids from these isolates were characterized by sequencing. Overall, 52 VVE isolates were identified, comprising 15% of all VRE isolates identified. Isolates demonstrated growth on Brilliance VRE agar (Oxoid) at 24 h of incubation but did not grow on brain heart infusion agar with 6 g/ml vancomycin (Oxoid) or bile esculin azide agar with 6 g/ml vancomycin (Oxoid) and were susceptible to vancomycin. Genotyping of 20 randomly selected VVE isolates revealed that 15/20 were identical, while 5 were highly related. PCR of the VVE transposon confirmed the presence of vanHAXY gene cluster; however, vanS (sensor) and vanR (regulator) genes were absent. The outbreak was controlled through routine infection control measures. We report an emergence of a fit strain of E. faecium containing vanA yet susceptible to vancomycin. Whether this new strain represents VRE has yet to be determined; however, unique testing procedures are required for reliable identification of VVE. Vancomycin-resistant enterococcus (VRE) colonization and infection are increasingly common in both hospital and outpatient settings. Since the initial discovery of VRE during the 1980s in the United Kingdom and France, it has spread to many countries throughout the world (1, 2). In Canada, there has been a small but steady increase in rates of detection of VRE from 0.37 case per 1,000 patient admissions in 1999 to 1.32 in 2005 (3). VRE infection rates increased from 0.02 to 0.05 case per 1,000 admitted patients. Six different types of glycopeptide resistance (vanA, vanB, vanC, vanD, vanE, and vanG) have been described, of which the vanA-and vanB-mediated types are clinically significant in enterococci. Typically, vanA-mediated vancomycin resistance is found in Enterococcus faecium. VRE resistance in vanA-bearing isolates is mediated by the group of genes vanR, vanS, vanH, vanA, and vanX, which are usually carried on the Tn1546 transposon. The expression of these genes leads to replacement of the C-terminal D-Ala residue with D-Lac during cell wall synthesis, thus modifying the vancomycin-binding target. The transposon is often contained on plasmids, making it easy to transfer among enterococcal strains. Historically, there has been little sequence variation in this gene cluster (4).Various studies have shown that infections caused by VRE lead to longer hospital stays, higher mortality, and significantly higher cost than infections caused by vancomycin-susceptible enterococci (5). Therefore, ac...

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“…One strain was susceptible to vancomycin and teicoplanin, whereas the other was resistant to vancomycin and teicoplanin, despite possessing the same structure of the Tn1546-like element. 18 Another study also reported a vancomycin-susceptible isolate missing the orf1, orf2, vanS, and vanR genes of the Tn1546-like element, similar to the vancomycin-resistant isolates reported in another study. 25,26 These results demonstrated that the occurrence of the VanB phenotypeevanA genotype might not completely depend on the genetic variation in the Tn1546-like elements.…”

Section: Discussionmentioning

confidence: 83%

“…13,14,17 Recent studies have found that two VREfm isolates have identical Tn1546-like element structures, however, one VREfm isolate was susceptible to teicoplanin and the other resistant, thus vancomycin resistance may not be dependent on the Tn1546-like element. 10,18 These findings prompted us to suspect that the occurrence of the VanB phenotypeevanA genotype VREfm might not be due to a single genetic variation, but due to vanA gene expression.…”

Section: Introductionmentioning

confidence: 98%

Comparison of vanA gene mRNA levels between vancomycin-resistant Enterococci presenting the VanA or VanB phenotype with identical Tn1546-like elements

Shen

Liu

et al. 2016

Journal of Microbiology, Immunology and Infection

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Loss of vancomycin resistance not completely dependent on the Tn1546 element in Enterococcus faecium isolates

Cited by 15 publications

References 15 publications

Evaluation of Three Rapid Diagnostic Methods for Direct Identification of Microorganisms in Positive Blood Cultures

Evaluation of Three Rapid Diagnostic Methods for Direct Identification of Microorganisms in Positive Blood Cultures

Outbreak of Vancomycin-Susceptible Enterococcus faecium Containing the Wild-Type vanA Gene

Comparison of vanA gene mRNA levels between vancomycin-resistant Enterococci presenting the VanA or VanB phenotype with identical Tn1546-like elements

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