Role of transposon Tn5482 in the epidemiology of vancomycin-resistant Enterococcus faecium in the pediatric oncology unit of a New York City Hospital.
ABSTRACT During a 36-month period between 1993 and 1995 in the Pediatric Oncology Unit of Memorial Sloan Kettering Cancer Center, 74 patients experienced episodes of infection or colonization caused by vancomycin-resistant enterococci (VRE). Characterization of the 74 bacterial isolates by microbiological and molecular techniques (pulsed-field gel electrophoresis and hybridization with DNA probes specific for the vanA and vanB genes and for IS1251) identified 73 Enterococcusfaecium and one Enterococcusfaecalis (vanB) among the primary VRE isolates. Most (69/73) of the E. faecium isolates carried vanA and four isolates, the vanB gene complex. The overwhelming majority (67/69) of the vanA -positive isolates also gave hybridization signal for IS1251, indicating the presence of the newly described conjugative transposon Tn5482. No hybridization with IS1251 was obtained with the four vanB-carrying isolates. About 30% of the vanA-positive strains (23/69) were represented by PFGE subtype variants of a single clone, most isolates of which were recovered during a 4-month period between April to June of 1994. The larger portion of the vanA-carrying VRE represented by close to 70% of the isolates (46/69) belonged to as many as 37 different clonal types, indicating tremendous genetic diversity. Among 67 of the 69 vanA-carrying isolates, the localization of the Tn5482-associated vanA gene complex could be unequivocally identified either on the chromosome (40/69) or in plasmids (27/69). Transconjugants recovered from filter mating experiments using either a chromosomally located or plasmid-borne vanA donor strain and a single vancomycin-susceptible strain of either E. faecium or E. faecalis were analyzed by molecular typing techniques. Seven out of 10 independent transconjugants recovered from the same cross showed extensive differences in PFGE pattern and also in the localization of the vanA hybridizing DNA fragment transferred from the common VRE donor with chromosomally located vanA. The observations suggest that the extensive genetic diversity observed among the clinical isolates of VRE may be generated during conjugation between vancomycin-resistant and -susceptible enterococcal isolates. The observations also suggest that the epidemic spread of VRE in the United States may be linked to the frequent presence of Tn5482 among the American isolates.
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ABSTRACT: SUMMARY Clinical and epidemiologic analysis of intestinal tract colonization with vancomycin-resistant enterococci in an intensive care unit. Intestinal tract colonization with vancomycin resistant enterococci (VRE) was studied during five months and 25 days. Out of 171 patients hospitalized in the intensive care unit, 124 (73%) were included in this study. Thirty five of them (28%) were recognized as colonized with VRE. VRE isolates (n = 35) were identified as Enterococcus faecium (n=18), Enterococcus gallinarum (n=16), and Enterococcus raffinosus (n=1). All of them were resistant to vancomycin (MIC90 = 512 µg/ml) and to teicoplanin (MIC90 = 32 µg/ml), having the vanA gene. By means of molecular methods a high homology was found among E. faecium and E. gallinarum isolates, respectively, suggesting their spread as a kind of outbreak. No significant differences in age or sex were found among colonized and non- colonized patients (p>0.05). On the other hand, the hospitalization time and the use of broad-spectrum antibiotics were associated with colonization. From this study we highlight the importance of enhancing all measures of control and prevention of hospital infections, carefully analyzing the empiric antimicrobial schemes, trying to reduce the hospital stage, and following the surveillance to evaluate the efficacy of such procedures.Revista Argentina de microbiología 03/2005; 37(1). · 0.66 Impact Factor
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ABSTRACT: Vancomycin-resistance in enterococci (VRE) is associated with isolates within ST18, ST17, ST78 Enterococcus faecium (Efm) and ST6 Enterococcus faecalis (Efs) human adapted lineages. Despite of its global spread, vancomycin resistance rates in enterococcal populations greatly vary temporally and geographically. Portugal is one of the European countries where Tn1546 (vanA) is consistently found in a variety of environments. A comprehensive multi-hierarchical analysis of VRE isolates (75 Efm and 29 Efs) from Portuguese hospitals and aquatic surroundings (1996-2008) was performed to clarify the local dynamics of VRE. Clonal relatedness was established by PFGE and MLST while plasmid characterization comprised the analysis of known relaxases, rep initiator proteins and toxin-antitoxin systems (TA) by PCR-based typing schemes, RFLP comparison, hybridization and sequencing. Tn1546 variants were characterized by PCR overlapping/sequencing. Intra- and inter-hospital dissemination of Efm ST18, ST132 and ST280 and Efs ST6 clones, carrying rolling-circle (pEFNP1/pRI1) and theta-replicating (pCIZ2-like, Inc18, pHTβ-like, two pRUM-variants, pLG1-like, and pheromone-responsive) plasmids was documented. Tn1546 variants, mostly containing ISEf1 or IS1216, were located on plasmids (30-150 kb) with a high degree of mosaicism and heterogeneous RFLP patterns that seem to have resulted from the interplay between broad host Inc18 plasmids (pIP501, pRE25, pEF1), and narrow host RepA_N plasmids (pRUM, pAD1-like). TAs of Inc18 (ω-ε-ζ) and pRUM (Axe-Txe) plasmids were infrequently detected. Some plasmid chimeras were persistently recovered over years from different clonal lineages. This work represents the first multi-hierarchical analysis of VRE, revealing a frequent recombinatorial diversification of a limited number of interacting clonal backgrounds, plasmids and transposons at local scale. These interactions provide a continuous process of parapatric clonalization driving a full exploration of the local adaptive landscape, which might assure long-term maintenance of resistant clones and eventually fixation of Tn1546 in particular geographic areas.PLoS ONE 03/2013; 8(3):e60589. · 3.53 Impact Factor
- Microbial drug resistance (Larchmont, N.Y.) 01/2000; 6(1):49-57. · 1.99 Impact Factor