Instituto Valenciano de Microbiología

Masía El Romeral
Ctra. de Bétera a San Antonio Km. 0.3
46117 Bétera (Valencia)
Phone. 96 169 17 02
Fax 96 169 16 37
CIF B-96337217


Resistance to glycopeptides (vancomycin and teicoplanin) in Enterococcus spp. Phenotypes VanA, VanB, vand, and other less frequent (VanC, C2 / 3, E, F, G, L, M) - Molecular diagnosis (PCR and sequencing).

Information 28-02-2015.


Glycopeptide resistance in Enterococcus spp. It is a major problem since its inception in the 1980s because of its importance as a major nosocomial pathogen. Glycopeptides vancomycin and teicoplanin, act by binding to the terminal dimer D-alanyl-D-alanine (D-Ala-D-Ala) of the final precursor for the formation of the peptidoglycan by inhibiting the formation of cross - links, by blocking the transglucosylation and transpeptidation.

Resistance in Enterococcus spp. It is a result of the synthesis of final precursors of peptidoglycan with low affinity to these antibiotics because these bacteria can synthesize a final precursor in which the native dimer D-Ala-D-Ala is replaced by other dimers as D-Ala- D-Lac (D-alanyl-D-lactose) or D-Ala-D-Ser (D-alanyl-D-serine). This new synthesis is mediated by group (cluster) of genes called van. They described seven kinds of sets of genes conferring resistance to Enterococcus where there are common genes, but also different genes and even different organization within the gene set. The types of gene sets (cluster) (resistance operon glycopeptides) are named according to the name of the gene encoding the ligase. There are up to 8 different types of ligase, although they differ in their sequences, can differentiate into the leading end dimer precursor: ligases D-Ala: D-Lac that generate the dimer D-Ala-D-Lac (encoded by vanA genes, vanB and vand), or D-Ala ligases: D-Ser, which leads to the final dimer precursor D-Ala-D-Ser (encoded by genes vanC, vanE, vanG and vanL).

Genes in different types "are"

Gene sets of vanA types, vanB and vand, generators dimer D-Ala-D-Lac contain genes for:

Gene sets types vanC, vanE, vanG and vanL generators dimer D-Ala-D-Ser, containing genes for:

The set of genes FNPV type, with FNPV ligase, it has only been found in Paenibacillus popilliae bacteria used in biopesticides, but not found in Enterococcus spp.

Genotypic sequence of some types "van"

The order of the genes operon glycopeptide resistance of some of these types are:

Phenotypic sensitivity characteristics of each set of type "van"

The vanA resistance type set is characterized by high - level resistance to vancomycin (> 64 mg / mL) and teicoplanin (> 16 mg / mL), and is inducible by vancomycin both, such as teicoplanin.

The resistance vanB set type is characterized by acquired resistance to various concentrations of vancomycin (4 ? 1.024 g / mL), but not teicoplanin, and vancomycin is only inducible.

These two types, vanA and vanB, are the two most common phenotypes of resistance to glycopeptides. The genes encoding vanA and vanB phenotypes are in a transposon (Tn1546) which may be in a plasmid or on the chromosome.

The vanC1 and vanC2 / C3 types are characterized by intrinsic low - level resistance to vancomycin (2 to 32 mg / mL), and sensitivity to teicoplanin. This resistance is inducible, so that in the absence of vancomycin, vanC strains synthesize the dimer D-alanyl-D-alanine.

The vanE type found in Enterococcus faecalis is characterized by low resistance to vancomycin (16 .mu.g / ml) and sensitivity to teicoplanin (0.5 .mu.g / mL).

The Vand type is characterized by intermediate vancomycin resistance (128 ug / mL) and low level teicoplanin and constitutively expressed. The Vand genes are on the chromosome and are not transferable, so are very rare vand strains, in contrast to the large area and high prevalence of vanA and vanB strains.

The vanG type found in Enterococcus faecalis has moderate resistance to vancomycin (12-16 mg / mL) and sensibililidad teicoplanin (0.5 .mu.g / mL).

The vanM type found in studying strains possessing no vanA genes, vanB, or Vand. These strains have a set of genes called vanM. The vanM type, has high resistance to vancomycin and teicoplanin, the latter with higher MICs teicoplanin, which has the vanA type.  

Tests in IVAMI


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