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Title: Molecular characterization of vanB elements in naturally occurring gut anaerobes.
Austin Authors: Ballard, Susan A;Pertile, Kelly K;Lim, M;Johnson, Paul D R ;Grayson, M Lindsay 
Affiliation: Infectious Diseases Department, Austin Health, Studley Rd., Heidelberg, Victoria 3084, Australia
Issue Date: 1-May-2005
Publication information: Antimicrobial Agents and Chemotherapy; 49(5): 1688-94
Abstract: Previously, we reported the isolation of 10 vancomycin-resistant gram-positive anaerobic bacilli carrying the vanB ligase gene from nine hemodialysis patients (S. A. Ballard et al., Antimicrob. Agents Chemother. 49:77-81, 2005; T. P. Stinear et al., Lancet 357:855-856, 2001). In the present study, the molecular and evolutionary relationship of the vanB resistance element within these 10 anaerobes and two vancomycin-resistant Enterococcus faecium strains were examined. PCR analysis and nucleotide sequencing demonstrated that all 12 isolates carried the vanB operon associated with an element identical to Tn1549 and Tn5382 of Enterococcus. Restriction fragment length polymorphism analysis of the vanB operon in these isolates revealed two distinct patterns, and sequencing showed that minor base differences existed. PCR amplification of the joint region of a circular intermediate was demonstrated in nine of these organisms, a finding indicative of an ability to excise and circularize, an intermediate step in transposition and conjugative transfer. Southern hybridization with a vanB-vanX(B) probe suggests that there is one insert of the transposon in all isolates. Sequence analysis of the integration site revealed distinct sequences: the Tn1549/5382 element within E. faecium was inserted within the host chromosome, whereas nucleotide sequences surrounding the Tn1549/5382 element in the 10 anaerobes showed no significant homology to sequences in the GenBank database. We demonstrate considerable similarity between the Tn1549/5382 element identified in 10 anaerobe isolates with that found in enterococci. The homology and potential to transpose suggest a recent horizontal transfer event may have occurred. However, the original direction of transposition and the mechanism involved remains unknown.
Gov't Doc #: 15855482
DOI: 10.1128/AAC.49.5.1688-1694.2005
Type: Journal Article
Subjects: Anti-Bacterial Agents.pharmacology
Bacteria, Anaerobic.genetics
Bacterial Proteins.genetics
Blotting, Southern
DNA Transposable Elements.genetics
DNA, Bacterial.genetics
Digestive System.microbiology
Drug Resistance, Bacterial
Electrophoresis, Gel, Pulsed-Field
Enterococcus faecium.drug effects.genetics
Microbial Sensitivity Tests
Molecular Sequence Data
Polymorphism, Restriction Fragment Length
Reverse Transcriptase Polymerase Chain Reaction
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