MOLECULAR CHARACTERIZATION OF VANCOMYCIN-RESISTANT ENTEROCOCCI FROM HOSPITALIZED-PATIENTS AND POULTRY PRODUCTS IN THE NETHERLANDS

Vancomycin-resistant enterococci (VRE) pose an emerging health risk, b ut 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 contaminati on of poultry products with VRE was determined, VRE were genotyped by pulsed-field gel electrophoresis (PFGE), and transposon structure mapp ing nas done by PCR, The vanX-vanY intergenic regions of several strai ns were further analyzed by sequencing. A total of 242 of 305 (79%) po ultry products were found to be contaminated with VRE, Of these VRE, 1 42 (59%) were high-level-vancomycin-resistant Enterococcus faecium str ains (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 overl ap was found when VREF from humans were compared with VREF from poultr y. Two vanA transposon types were identified among poultry strains. In 59 of 142 (42%) of the poultry VREF, the size of the intergenic regio n between vanX and vanY was similar to 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 demonstra ted full sequence conservation. Though preliminary, these data suggest that dissemination of the resistance genes carried on transposable el ements may be of greater importance than clonal dissemination of resis tant strains. This observation is important for developing strategies to control the spread of glycopeptide resistance.