The first report of the vanC1 gene in Enterococcus faecium isolated from a human clinical specimen

The vanC1 gene, which is chromosomally located, confers resistance to vancomycin and serves as a species marker for Enterococcus gallinarum. Enterococcus faecium TJ4031 was isolated from a blood culture and harbours the vanC1gene. Polymerase chain reaction (PCR) assays were performed to detect vanXYc and vanTc genes. Only the vanXYc gene was found in the E. faecium TJ4031 isolate. The minimum inhibitory concentrations of vancomycin and teicoplanin were 2 µg/mL and 1 µg/mL, respectively. Real-time reverse transcription-PCR results revealed that the vanC1and vanXYc genes were not expressed. Pulsed-field gel electrophoresis and southern hybridisation results showed that the vanC1 gene was encoded in the chromosome. E. faecalis isolated from animals has been reported to harbour vanC1gene. However, this study is the first to report the presence of the vanC1gene in E. faecium of human origin. Additionally, our research showed the vanC1gene cannot serve as a species-specific gene of E. gallinarum and that it is able to be transferred between bacteria. Although the resistance marker is not expressed in the strain, our results showed that E. faecium could acquire the vanC1gene from different species.

Detection of vanC 1 gene transcription in vancomycin-susceptible Enterococcus faecalis

Here we report the presence and expression levels of the vanC 1 and vanC 2/3 genes in vancomycin-susceptible strains of Enterococcus faecalis. The vanC 1 and vanC 2/3 genes were located in the plasmid DNA and on the chromosome, respectively. Specific mRNA of the vanC 1 gene was detected in one of these strains. Additionally, analysis of the vanC gene sequences showed that these genes are related to the vanC genes of Enterococcus gallinarum and Enterococcus casseliflavus. The presence of vanC genes is useful for the identification of E. gallinarum and E. casseliflavus. Moreover, this is the first report of vanC mRNA in E. faecalis.

Risk factors for vancomycin-resistant enterococci colonisation in critically ill patients

Vancomycin-resistant enterococci (VRE) are important hospital pathogens and have become increasingly common in patients admitted to the intensive care unit (ICU). To determine the incidence and the risk factors associated with VRE colonisation among ICU patients, active surveillance cultures for VRE faecal carriages were carried out in patients admitted to the ICU of the University Hospital of Uberlândia, Minas Gerais, Brazil. Risk factors were assessed using a case-control study. Seventy-seven patients (23.1 percent) were found to be colonised with vanC VRE and only one patient (0.3 percent) was colonised with vanA VRE. Independent risk factors for VRE colonisation included nephropathy [odds ratio (OR) = 13.6, p < 0.001], prior antibiotic use (OR = 5.5, p < 0.03) and carbapenem use (OR = 17.3, p < 0.001). Our results showed a higher frequency (23.1 percent) of Enterococcus gallinarum and Enterococcus casseliflavus, species that are intrinsically resistant to low levels of vancomycin (vanC), without an associated infection, associated with prior antibiotic use, carbapenem use and nephropathy as comorbidity. This study is the first to demonstrate the risk factors associated with vanC VRE colonisation in ICU hospitalised patients. Although vanA and vanB enterococci are of great importance, the epidemiology of vanC VRE needs to be better understood. Even though the clinical relevance of vanC VRE is uncertain, these species are opportunistic pathogens and vanC VRE-colonised patients are a potential epidemiologic reservoir of resistance genes.

Clinical Features and Rate of Infective Endocarditis in Non-Faecalis and Non-faecium Enterococcal Bacteremia / 전남의대학술지

Non-faecalis and non-faecium enterococci are an occasional cause of bacteremia, and some cases of infective endocarditis caused by these pathogens have been reported. However, the rate of infective endocarditis in non-faecalis and non-faecium enterococcal bacteremia is still undetermined. We compared the clinical features and the rate of infective endocarditis of 70 cases of non-faecalis and non-faecium enterococcal bacteremia with those of 65 cases of Enterococcus faecalis bacteremia. Non-faecalis and non-faecium enterococcal bacteremia was more frequently associated with biliary tract infection and polymicrobial bacteremia, and was less frequently associated with infective endocarditis, than was E. faecalis bacteremia (57% vs. 28%, p<0.01; 47% vs. 31%, p=0.05; 1% vs. 14%, p<0.01, respectively).

Clinical Features and Rate of Infective Endocarditis in Non-Faecalis and Non-faecium Enterococcal Bacteremia / 전남의대학술지

Non-faecalis and non-faecium enterococci are an occasional cause of bacteremia, and some cases of infective endocarditis caused by these pathogens have been reported. However, the rate of infective endocarditis in non-faecalis and non-faecium enterococcal bacteremia is still undetermined. We compared the clinical features and the rate of infective endocarditis of 70 cases of non-faecalis and non-faecium enterococcal bacteremia with those of 65 cases of Enterococcus faecalis bacteremia. Non-faecalis and non-faecium enterococcal bacteremia was more frequently associated with biliary tract infection and polymicrobial bacteremia, and was less frequently associated with infective endocarditis, than was E. faecalis bacteremia (57% vs. 28%, p<0.01; 47% vs. 31%, p=0.05; 1% vs. 14%, p<0.01, respectively).

An Enterococcus gallinarum Strain Carrying Both vanA and vanC1 Genes / 대한임상병리학회지

Enterococcus gallinarum carrying both vanA and vanC1 genes were detected from a surveillance culture from a patient staying at the surgical intensive care unit for a few years. E. gallinarum, SI04, was highly resistant to vancomycin (MIC of >or=256ng/mL) and teicoplanin (MIC of >or=256ng/mL). Multiplex PCR for vanA, vanB, vanC1 and vanC2/3 genes revealed SI04 to be positive for both vanA and vanC1 genes. This finding supports the fact that genotyping is needed to classify vancomycin-resistant enterococci (VRE). This is the first report on VanC VRE accompanying vanA gene in Korea.

Comparison of Antimicrobial Susceptibility Testing Methods to Detect Glycopeptide Resistance in Enterococci: E-test, Vitek, Disk Diffusion and Agar Dilution Method / 대한임상병리학회지

BACKGROUNDS: The emergence of resistant strains to glycopeptide in enterococci(GRE) is increasingly serious problem in the worldwide. Automated methods and disk diffusion test have difficulties in detecting vancomycin resistance of some strains of vancomycin-resistant enterococci(VRE), especially having vanC genotypes. And a few studies have been done assessing the ability of antimicrobial susceptibility testing methods to detect teicoplanin resistance in enterococci. METHODS: We evaluated the abilities of two commercial kits including Vitek GPS-IZ(BioMerieux, Vitek, Inc., USA) and E-test(AB Biodisk, USA), and disk diffusion test to detect glycopeptide resistance using 34 strains of vanA and 15 strains of vanC1/C2 VRE. We compared the results with those of standard agar dilution test. RESULTS: In detecting vancomycin resistance, no very major or major errors were seen, and minor error rates were observed with disk diffusion(25%), Vitek GPS-IZ(20%) and E-test(8%). Overall sensitivities of all three methods in detecting vancomycin resistance of vanA VRE were 97-100%, but sensitivities in detecting vancomycin resistance of vanC VRE were 20% in disk diffusion, 87% in E-test and 87% in Vitek GPS-IZ. In detecting teicoplanin resistance, very major error rate was high in Vitek GPS-IZ(47%), but no very major or major errors were seen in disk diffusion and E-test; minor error rates of 2% and 6% were seen in Vitek GPS-IZ and E-test, respectively. CONCLUSION: All three methods detect vancomycin resistance of vanA VRE, but they continue to demonstrate problems in detecting low-level vancomycin resistance and the Vitek GPS-IZ is difficult to detect teicoplanin resistance in enterococci.

Biochemical Tests for Differential Identification of Enterococci with VanC phenotype / 대한임상미생물학회지

BACKGROUND: Pigment production and acidification of ribose are most frequently used biochemical tests for the differentiation of three enterococcal species carrying vanC genes such as Enterococcus gallinarum, Enterococcus casseliflavus, and Enterococcus flavescens. However, pigment production may occasionally be negative in E. casseliflavus, and some of E. casseliflavus may be negative or delayed reaction with ribose fermentation test. So, we performed this study to find out biochemical tests capable of distinguishing the strains possessing vanC genotypes. METHOD: A total of 17 enterococci composed of 14 clinical isolates with motility or pigment positive strains and three ATCC strains(E. gallinarum ATCC 49573, E. casseliflavus ATCC 25788, and E. flavescens ATCC 49997) Were tested by multiplex PCR of the vanC genes(vanC-1, vanC-2 and vanC-3)and various biochemical tests. RESULTS: Among the 17 isolates including three ATCC control strains, four were genotyped as VanC-1, 11 were VanC-2, one were vanC-2/3, and any of vanC genes were not detected in one clinical isolate, respectively, Among the enterococci with vanC genotype, acid production from alphaD-cyclodextrin and hippurate hydrolysis were positive only in VanC-1 gneotype(E. gallinarum), acid production from glycerol and methyl-alpha-D-mannopyranoside were positive only in vanC-2 genotype(E. casseliflavus), and acid production from rhamnose and pigment production were negative only in VanC-1 genotype. Acid production from alphaD-cyclodextrin was negative only in vanC-2 genotype. The positive rate of ribose fermentation of VanC-1, VanC-2, and VanC-2/3(E. flavescens) genotype were 100%, 82%, and 0%, respectively. CONCLUSION: Acid production from rhamnose, alphaD-cyclodextrin, betaD-cyclodextrin, glycerol and methly-alphaD-mannopyranoside, pigment production, and hippurate hydrolysis test were useful biochemical tests for differentitating E. gallinarum form E. casseliflavus. The production of acid from alphaD-cyclodextrin, glycerol, methyl-alpha-D-mannopyranoside and were suitable biochemical tests for differentiating E. casseliflavus from E. flavescens.

Use of Methyl-alpha-D-glucopyranoside Test for Species Identification of Vancomycin Resistant Enterococci / 대한임상미생물학회지

BACKGROUND: The precise identification of Enterococcus gallinarum and E. casseliflavus has assumed additional importance in clinical microbiology due to the intrinsic low-level resistance to vancomycin and the difficulty in differentiating them from E. faecium or E. faecalis, which are frequently found to be clinically significant vancomycin resistant enterococci(VRE). We evaluated the usefulness of Methyl-alpha-D-glucopyranoside(MDG) test for accurate species identification among them. METHODS: A total of 23 enterococci isolates including 18 clinical isolates of VRE from Nov 1997 to Aug 1998 and 5 VRE strains which had previously been reported as E. faecalis (2), E. faecium(2), E. avium(1) carrying vanC were tested for acidification of MDG. MDG test was done using 1% MDG in phenol red broth base and yellow coloration was interpreted as positive after 1 and 2 days of incubation at 35 degrees C. MDG results were compared with species identification by MicroScan Pos Combo type 6 (Dade, US A), motility test, pigment production, and PCR results of vanA, vanB, vanC1, vanC2/C3. RESULTS: Vancomycin resistance of 23 strains were genotyped as 7 strains of vanA, 12 strains of vanC1, 4 strains of vanC2/C3. MicroScan identified 7 vanA VRE as E. faecalis(1) and E. faecium(6), 12 VRE carrying vanC1 as E. faecalis(3), E. faecium(8) and E. avium(1), and 4 VRE carrying vanC2/C3 as E faecalis(3) and E. avium(1). Sixteen vanC VRE strains were all positive for MDG test and only 8(50%) of the 16 strains were motile. Yellow pigment were detected in all 4 vanC2/C3 VRE but only after a careful examination with a prolonged incubation. Seven vanA VRE were all negative in MDG tests, motility test and pigment production. CONCLUSIONS: MicroScan system plus motility and pigment production test was not able to differentiate reliably E. gallinarum and E. casseliflavus from E. faecalis and E. faecium. The MDG test was shown to be superior to motility test in differentiating those from E. faecalis and E. faecium. We conclude that the MDG test should be included for identifcation of VRE.

Vancomycin-resistant Enterococci: Incidence, Antimicrobial Susceptibility, and Resistance Genotypes / 대한임상병리학회지

BACKGROUND: Infections caused by vancomycin-resistant enterococci (VRE) are becoming increasingly prevalent throughout the world. VRE can spread by direct patient-to-patient contact as well as on the hands of personnel and contaminated environmental surfaces. The purpose of this study was to examine the incidence of VRE among total enterococci from clinical specimen and investigate the antimicrobial characteristics and resistance genotypes of isolated VRE. METHODS: A total of 790 enterococcal isolates from patients over a period of 12 months were screened for vancomycin resistance using brain heart infusion agar plates supplemented with 6 g/mL of vancomycin. The incidence of VRE among enterococcal isolates was calculated from microbiology statistics program. Twenty three isolates of VRE were tested for minimal inhibitory concentrations (MIC) of vancomycin, penicillin, and gentamicin and resistance genotypes. RESULTS: In the first half period, the incidence of VRE was 1.9%, and in the second half, the incidence increased to 7.7%. Thirteen strains were found to be highly resistant to vancomycin, penicillin and gentamicin (MIC, >128 g/mL). According to the direct PCR analyses, the frequency of vanB, vanC1, and vanC2 types was 13, 7, and 3 strains, respectively. CONCLUSIONS: Continued vigilance, strict enforcement of infection control, and curtailment of vancomycin use seem to be our best approaches to controlling this increasingly important problem. For this purposes, accurate and timely detection of vancomycin-resistance and periodic investigation for incidence are essential.