Molecular characterization of vancomycin-resistant enterococci from hospitalized patients and poultry products in The Netherlands - PubMed (original) (raw)

Molecular characterization of vancomycin-resistant enterococci from hospitalized patients and poultry products in The Netherlands

N van den Braak et al. J Clin Microbiol. 1998 Jul.

Abstract

Vancomycin-resistant enterococci (VRE) pose an emerging health risk, but little is known about the precise epidemiology of the genes coding for vancomycin resistance. To determine whether the bacterial flora of consumer poultry serves as a gene reservoir, the level of contamination of poultry products with VRE was determined. VRE were genotyped by pulsed-field gel electrophoresis (PFGE), and transposon structure mapping was done by PCR. The vanX-vanY intergenic regions of several strains were further analyzed by sequencing. A total of 242 of 305 (79%) poultry products were found to be contaminated with VRE. Of these VRE, 142 (59%) were high-level-vancomycin-resistant Enterococcus faecium strains (VREF). PFGE revealed extensive VREF heterogeneity. Two genotypes were found nationwide on multiple occasions: type A (22 of 142 VREF [15%]) and type B (14 of 142 VREF [10%]). No PFGE-deduced genetic overlap was found when VREF from humans were compared with VREF from poultry. Two vanA transposon types were identified among poultry strains. In 59 of 142 (42%) of the poultry VREF, the size of the intergenic region between vanX and vanY was approximately 1,300 bp. This transposon type was not found in human VREF. In contrast, all human strains and 83 of 142 (58%) of the poultry VREF contained an intergenic region 543 bp in size. Sequencing of this 543-bp intergenic vanX-vanY region demonstrated full sequence conservation. Though preliminary, these data suggest that dissemination of the resistance genes carried on transposable elements may be of greater importance than clonal dissemination of resistant strains. This observation is important for developing strategies to control the spread of glycopeptide resistance.

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Figures

FIG. 1

FIG. 1

PFGE patterns for 15 VREF isolated from poultry products collected by the Dutch Food Inspection Services in Zutphen, The Netherlands. Molecular lengths of the markers are indicated on the right.

FIG. 2

FIG. 2

PFGE patterns of two epidemic genotypes of VREF. Lanes 1 to 4, genotype A; lanes 5 to 8, genotype B. These genotypes were frequently found by most of the food inspection services. Molecular lengths of the markers are indicated on the right.

FIG. 3

FIG. 3

Phylogenetic tree constructed on the basis of several PFGE types of VREF derived from poultry products (originating from Den Bosch, Goes, and Nijmegen, The Netherlands) and humans (20). The arrow indicates the highest level of homology between VRE from poultry and humans (Goes 175 and Goes 178 versus 10a). Type A is the epidemic PFGE type among poultry clusters, and strains have a high level of homology (Den Bosch 155 to Goes 84). Type M is the type that was encountered among humans relatively frequently [20]).

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