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Patrice Courvalin - One of the best experts on this subject based on the ideXlab platform.
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vancomycin resistance in enterococci due to synthesis of precursors terminating in d alanyl d serine
Antimicrobial Agents and Chemotherapy, 2005Co-Authors: Peter E Reynolds, Patrice CourvalinAbstract:the intrinsically glycopeptide-resistant Enterococcus gallinarum, Enterococcus casseliflavus, and Enterococcus flavescens (VanC type) and is present in the VanE and VanG types in which E. faecalis has acquired the genes encoding vancomycin resistance. Some of the enzymes implicated in this second resistance mechanism are different from those involved in high-level resistance, indicating a second route by which resistance has evolved. The basis of resistance results from the sixfold-lower affinity of vancomycin for acyl-D-Ala-D-Ser than for acyl-D-Ala-D-Ala (13) because of the increased bulk of the hydroxymethyl group of serine relative to the methyl group of alanine.
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Emergence of high-level resistance to glycopeptides in Enterococcus gallinarum and Enterococcus casseliflavus.
Antimicrobial Agents and Chemotherapy, 1994Co-Authors: S Dutkamalen, B. Blaimont, Georges Wauters, Patrice CourvalinAbstract:Enterococcus gallinarum BM4231 and Enterococcus casseliflavus BM4232, isolated from the feces of a patient under oral therapy with vancomycin, were resistant to high levels of vancomycin (MICs of >256 mu g/ml) and teicoplanin (MICs of 128 and 64 mu g/ml, respectively). This phenotype is new for these bacterial species that are naturally resistant to low levels of vancomycin and appears to be due to in vivo acquisition of plasmid pIP218 carrying the vanA gene cluster.
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the vanb gene confers various levels of self transferable resistance to vancomycin in enterococci
The Journal of Infectious Diseases, 1993Co-Authors: Richard Quintiliani, Stefan Evers, Patrice CourvalinAbstract:Thirty-nine strains of Enterococcus faecium and Enterococcus faecalis resistant to vancomycin and susceptible to teicoplanin on disk susceptibility testing (phenotypic class B) were isolated in 15 hospitals in Europe and the United States. The MICs of vancomycin for these strains ranged from 4 to 1024 micrograms/mL. Part of the vancomycin resistance gene vanB from E. faecalis V583 hybridized with a single but variably sized HindIII-KpnI fragment of total DNA from all 39 strains. This indicates that a single class of resistance determinants accounts for the VanB phenotype. No hybridization was detected with DNA from intrinsically resistant Enterococcus gallinarum or Enterococcus casseliflavus. Hybridization with DNA from enterococcal strains susceptible to or with acquired resistance to vancomycin and teicoplanin was not observed. The genes conferring resistance to vancomycin were self-transferable to other Enterococcus strains in 14 of the 39 strains. It thus appears that vanB confers various levels of conjugative vancomycin resistance in enterococci.
Paula Teixeira - One of the best experts on this subject based on the ideXlab platform.
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virulence factors among enterococci isolated from traditional fermented meat products produced in the north of portugal
Food Control, 2010Co-Authors: Joana Barbosa, Paul A Gibbs, Paula TeixeiraAbstract:Abstract The aim of this work was to characterize Enterococcus spp. isolated from Alheira, Chourica de Vinhais and Salpicao de Vinhais, fermented meat products produced in the North of Portugal, concerning their potential pathogenicity. One hundred and eighty two isolates (76 identified as Enterococcus faecalis, 44 as Enterococcus faecium, 1 as Enterococcus casseliflavus and 61 as Enterococcus spp.) were studied. Twenty six percent of isolates were gelatinase producers. None of the isolates produced lipase nor DNase activities. Hemolytic activity using sheep and human blood from two types (A and O) was assessed. One isolate was β-hemolytic in human blood. Results obtained in sheep blood were quite different from those obtained in human blood. Biofilm production in batch and in fed-batch mode was evaluated. In batch mode, only 28.0% and 3.9% of isolates were classified as moderate and strong biofilm producers, respectively, and in fed-batch mode, 35.7% and 63.2% of isolates were classified as moderate and strong biofilm producers, respectively. The presence of 13 virulence genes (efaAfs, efaAfm, esp, agg, cylM, cylB, cylA, cylLL cylLs and gelE) were investigated by PCR. The majority of enterococcal isolates showed the presence of one or more virulence factors, the most frequent genotype being efaAfs+ gelE+ agg+ (41.5%). E. faecalis isolates harbored multiple virulence traits, while E. faecium isolates were generally free of virulence determinants. Phenotypic and genotypic evidence of potential virulence factors were identified in Enterococcus spp. isolates, which is a reason of concern.
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antibiotic susceptibility of enterococci isolated from traditional fermented meat products
Food Microbiology, 2009Co-Authors: Joana Barbosa, Vânia Ferreira, Paula TeixeiraAbstract:Antibiotic susceptibility was evaluated for 182 Enterococcus spp. isolated from Alheira, Chourica de Vinhais and Salpicao de Vinhais, fermented meat products produced in the North of Portugal. Previously, a choice was made from a group of 1060 isolates, using phenotypic and genotypic tests. From these, 76 were previously identified as Enterococcus faecalis, 44 as Enterococcus faecium, one as Enterococcus casseliflavus and 61 as Enteroccocus spp. In order to encompass several of the known chemical and functional classes of antibiotics, resistance to ampicillin, penicillin G, ciprofloxacin, chloramphenicol, erythromycin, nitrofurantoin, rifampicin, tetracycline and vancomycin was evaluated. All the isolates were sensitive to antibiotics of clinical importance, such as penicillins and vancomycin. Some differences in Minimal Inhibitory Concentrations (MICs) of antibiotics, could be associated with the enterococcal species.
P Courvalin - One of the best experts on this subject based on the ideXlab platform.
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analysis of genes encoding d alanine d alanine ligase related enzymes in Enterococcus casseliflavus and Enterococcus flavescens
Antimicrobial Agents and Chemotherapy, 1994Co-Authors: Ferran Navarro, P CourvalinAbstract:Using degenerate oligonucleotides complementary to sequences encoding conserved amino acid motifs in D-alanine-D-alanine (Ddl) ligases, we have amplified ca. 600-bp fragments from Enterococcus casseliflavus ATCC 25788 and Enterococcus flavescens CCM439. Sequence analysis of the amplification products indicated that each strain possessed two genes, ddlE. cass. and vanC-2, and ddlE. flav. and vanC-3, respectively, encoding Ddl-related enzymes. The fragments internal to the vanC genes were 98.3% identical. The vanC-2 gene was cloned into Escherichia coli and sequenced. Extensive similarity (66% nucleotide identity) was detected between this gene and vanC-1 from Enterococcus gallinarum (S. Dutka-Malen, C. Molinas, M. Arthur, and P. Courvalin, Gene 112:53-58, 1992), suggesting that the vanC genes are required for intrinsic low-level resistance to vancomycin. The partial deduced amino acid sequences of ddlE. cass. and ddlE. flav. were identical and closely related to that of the Ddl ligase of Enterococcus faecalis (79% identity). In Southern hybridization experiments, only DNA from E. casseliflavus and E. flavescens hybridized to probes internal to the vanC-2 and ddlE. cass. genes.
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vancomycin resistance gene vanc is specific to Enterococcus gallinarum
Antimicrobial Agents and Chemotherapy, 1992Co-Authors: Roland Leclercq, S Dutkamalen, J Duval, P CourvalinAbstract:Nearly all strains of Enterococcus gallinarum are resistant to low levels of vancomycin. The glycopeptide resistance gene vanC from E. gallinarum BM4174 has recently been cloned and sequenced. A probe specific for vanC hybridized with a 2.7-kb EcoRI and a 4.5-kb HindIII fragment of total DNA from the 42 strains of E. gallinarum studied. No homology was detected with DNA of strains belonging to other species intrinsically resistant to vancomycin, including Enterococcus casseliflavus, a species that expresses a vancomycin resistance phenotype similar to that of E. gallinarum. No hybridization with DNA of enterococcal strains with acquired resistance to high or low levels of vancomycin was observed. The specificity of the vanC probe allowed us to distinguish E. gallinarum from 12 other species of enterococci, indicating that this probe is a useful tool for species identification within the genus Enterococcus.
Peter E Reynolds - One of the best experts on this subject based on the ideXlab platform.
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vancomycin resistance in enterococci due to synthesis of precursors terminating in d alanyl d serine
Antimicrobial Agents and Chemotherapy, 2005Co-Authors: Peter E Reynolds, Patrice CourvalinAbstract:the intrinsically glycopeptide-resistant Enterococcus gallinarum, Enterococcus casseliflavus, and Enterococcus flavescens (VanC type) and is present in the VanE and VanG types in which E. faecalis has acquired the genes encoding vancomycin resistance. Some of the enzymes implicated in this second resistance mechanism are different from those involved in high-level resistance, indicating a second route by which resistance has evolved. The basis of resistance results from the sixfold-lower affinity of vancomycin for acyl-D-Ala-D-Ser than for acyl-D-Ala-D-Ala (13) because of the increased bulk of the hydroxymethyl group of serine relative to the methyl group of alanine.
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biochemical and genetic characterization of the vanc 2 vancomycin resistance gene cluster of Enterococcus casseliflavus atcc 25788
Antimicrobial Agents and Chemotherapy, 2002Co-Authors: Ireena Dutta, Peter E ReynoldsAbstract:The vanC-2 cluster of Enterococcus casseliflavus ATCC 25788 consisted of five genes (vanC-2, vanXY(C-2), vanT(C-2), vanR(C-2), and vanS(C-2)) and shared the same organization as the vanC cluster of E. gallinarum BM4174. The proteins encoded by these genes displayed a high degree of amino acid identity to the proteins encoded within the vanC gene cluster. The putative D,D-dipeptidase-D,D-carboxypeptidase, VanXY(C-2), exhibited 81% amino acid identity to VanXY(C), and VanT(C-2) displayed 65% amino acid identity to the serine racemase, VanT. VanR(C-2) and VanS(C-2) displayed high degrees of identity to VanR(C) and VanS(C), respectively, and contained the conserved residues identified as important to their function as a response regulator and histidine kinase, respectively. Resistance to vancomycin was expressed inducibly in E. casseliflavus ATCC 25788 and required an extended period of induction. Analysis of peptidoglycan precursors revealed that UDP-N-acetylmuramyl-L-Ala-delta-D-Glu-L-Lys-D-Ala-D-Ser could not be detected until several hours after the addition of vancomycin, and its appearance coincided with the resumption of growth. The introduction of additional copies of the vanT(C-2) gene, encoding a putative serine racemase, and the presence of supplementary D-serine in the growth medium both significantly reduced the period before growth resumed after addition of vancomycin. This suggested that the availability of D-serine plays an important role in the induction process.
Joana Barbosa - One of the best experts on this subject based on the ideXlab platform.
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virulence factors among enterococci isolated from traditional fermented meat products produced in the north of portugal
Food Control, 2010Co-Authors: Joana Barbosa, Paul A Gibbs, Paula TeixeiraAbstract:Abstract The aim of this work was to characterize Enterococcus spp. isolated from Alheira, Chourica de Vinhais and Salpicao de Vinhais, fermented meat products produced in the North of Portugal, concerning their potential pathogenicity. One hundred and eighty two isolates (76 identified as Enterococcus faecalis, 44 as Enterococcus faecium, 1 as Enterococcus casseliflavus and 61 as Enterococcus spp.) were studied. Twenty six percent of isolates were gelatinase producers. None of the isolates produced lipase nor DNase activities. Hemolytic activity using sheep and human blood from two types (A and O) was assessed. One isolate was β-hemolytic in human blood. Results obtained in sheep blood were quite different from those obtained in human blood. Biofilm production in batch and in fed-batch mode was evaluated. In batch mode, only 28.0% and 3.9% of isolates were classified as moderate and strong biofilm producers, respectively, and in fed-batch mode, 35.7% and 63.2% of isolates were classified as moderate and strong biofilm producers, respectively. The presence of 13 virulence genes (efaAfs, efaAfm, esp, agg, cylM, cylB, cylA, cylLL cylLs and gelE) were investigated by PCR. The majority of enterococcal isolates showed the presence of one or more virulence factors, the most frequent genotype being efaAfs+ gelE+ agg+ (41.5%). E. faecalis isolates harbored multiple virulence traits, while E. faecium isolates were generally free of virulence determinants. Phenotypic and genotypic evidence of potential virulence factors were identified in Enterococcus spp. isolates, which is a reason of concern.
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antibiotic susceptibility of enterococci isolated from traditional fermented meat products
Food Microbiology, 2009Co-Authors: Joana Barbosa, Vânia Ferreira, Paula TeixeiraAbstract:Antibiotic susceptibility was evaluated for 182 Enterococcus spp. isolated from Alheira, Chourica de Vinhais and Salpicao de Vinhais, fermented meat products produced in the North of Portugal. Previously, a choice was made from a group of 1060 isolates, using phenotypic and genotypic tests. From these, 76 were previously identified as Enterococcus faecalis, 44 as Enterococcus faecium, one as Enterococcus casseliflavus and 61 as Enteroccocus spp. In order to encompass several of the known chemical and functional classes of antibiotics, resistance to ampicillin, penicillin G, ciprofloxacin, chloramphenicol, erythromycin, nitrofurantoin, rifampicin, tetracycline and vancomycin was evaluated. All the isolates were sensitive to antibiotics of clinical importance, such as penicillins and vancomycin. Some differences in Minimal Inhibitory Concentrations (MICs) of antibiotics, could be associated with the enterococcal species.