Research of vancomycin resistance, adherence factors, and conjugative plasmids of enterococci

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(1) A total of 640 vancomycin resistant Enterococcus faecium (VRE) isolates were examined for the conjugative gentamicin resistance plasmid. Four hundred ninety-two (77 %) of the strains exhibited resistance to concentrations of gentamicin from 64 mg/ml (MIC) to greater than 1024 mg/ml (MIC). The gentamicin resistance of each of 261 (53 %) of the 492 gentamicin resistant strains was transferred to E. faecium strain at a frequency of about 10^<-5> to 10^<-6> per donor cell in broth mating. The conjugative gentamicin resistance plasmids were identified and were classified into five types (A through E) with respect to their EcoRI restriction profiles. The EcoRI or NdeI restriction fragments of each type of plasmids hybridized to the conjugative gentamicin resistance plasmid pMG1 (65.1 kb), which was originally isolated from an E. faecium clinical isolate, and transfer efficiently in broth mating.(2) The adherence of Enterococcus faecalis strains to human T24 cells was examined by scanning … More electron microscopy. Five highly adhesive strains were identified from 30 strains isolated from the urine of patients with urinary tract infections. The five isolated strains also adhered efficiently to human bladder epithelial cells. The adhesiveness of these strains was inhibited by treatment with fibronectin or trypsin, implying that a specific protein (adhesin) on the bacterial cell surface mediates adherence to fibronectin on the host cell surfaces, and the adhesin differs from the reported adhesins.(3) pMG1 (65.1 kbp) is a pheromone-independent Enterococcus faecium conjugative plasmid conferring gentamicin resistance. To analyze the regulation of tra gene expression in pMG1, transcripts of pMG1 were examined during conjugation. One transcript of gene 71ORF2 increased to its maximum level at 20 min after the start of mating. This increase was not observed in cultures of the donor cell or recipient cell. The transfer frequency of the mutant plasmid pMG229, which had a disrupted 71ORF2 gene on pMG1, or the parent pMG1 was 1.6x10^<-7> or 1.1x10^<-3> per donor cell, respectively, in broth mating, and the transfer frequency of pMG229 and pMG1 was 2.7x10^<-3> or 8.5x10^<-2> per donor cell, respectively, in filter mating. 71ORF2 is a gene involved in the tra gene system for conjugation, and the product of the gene was associated with the formation or stabilization of mating aggregates during broth mating. Less