Horizontal transfer and integration of large chromosomal elements among Gram positive bacteria.

Project leader(s)   Johanna E. Sollid

Co-workers / Project staff
Arnfinn Sundsfjord, professor
Johanna E. Sollid, ass. professor
Kristin H. Dahl, researcher
Trine J. Tessem, technician
Anne-Merethe Hanssen, post doc
Eva K. Bjørkeng, PhD student
Jinglu Sun, PhD student
J. Pauline Cavanagh, master student

Main Objects:
The impact of antimicrobial resistant bacteria .....

Project outline
The impact of antimicrobial resistant bacteria is accumulating worldwide. In this perspective it is important to elucidate factors and mechanisms involved in the evolution and spread of multidrug-resistant pathogenic bacteria. Enterococci are considered “difficult to treat” pathogens among Gram-positive bacteria. Both inherent antimicrobial resistances and a striking propensity to acquire additional resistance are well known characteristics.
Extensive HGT does occur in enterococci. They are not considered naturally transformable and only indirect evidence for transduction has been provided. But a diverse set of conjugative elements has been described. Independent observations suggest the presence of chromosome-to-chromosome gene flux mechanisms in enterococci enabling transfer of large chromosomal elements containing antimicrobial resistance determinants and/or housekeeping genes. Tnvamp, a ³200 kb Tn5382 (vanB2) containing element, was found to transfer housekeeping genes between Enterococcus strains. Recently, a 100 kb Tn5382 (vanB2) containing element was shown to be transferred from Streptococcus luteus to enterococci.
Previously described mechanisms cannot explain the observed transfer of chromosomal vanB-containing elements observed in our laboratory. Thus, we are looking for other unidentified transfer mechanisms that could explain those intriguing observations.
Our main hypothesis is that Gram-positive bacteria harbours unidentified chromosomal recombination and DNA transfer mechanisms that are important in the evolution of epidemic multi-resistant bacteria. We are searching for structural elements that may support such mechanisms to examine their function.

National/international collaborator(s)

Professor Ingolf F. Nes, and Dr Ågot Aakra. Laboratory of Microbial Gene Technology, Department of Chemistry, Biotechnology and Food Science, Norwegian University of Life Sciences. Ås, Norway.
Professor Nina Langeland and Stein Christian Mohn. Institute of Medicine, Haukeland University Hospital, University of Bergen, Bergen, Norway.

Funding
Research Council of Norway (NFR)
Helse-Nord RHF

Publications
Dahl K.H. 2000. Structure and mobility of the vanB operon in Enterococci. Thesis. University of Tromsø, Norway.

Dahl, K.H., E.W. Lundblad, T.P. Røkenes, Ø. Olsvik, and A. Sundsfjord. 2000. Genetic linkage of the vanB2 gene cluster to Tn5382 in vancomycin-resistant enterococci and characterization of two novel insertion sequences. Microbiology 146:1469-1479.

Dahl, K.H., T.P. Røkenes, E.W. Lundblad, and A. Sundsfjord. 2003. Nonconjugative transposition of the vanB-containing Tn5382-like element in Enterococcus faecium. Antimicrob. Agents Chemother. 47: 786-789.

Dahl, K.H., and A. Sundsfjord. 2003. Tn5382-Like Transferable vanB2 Tn5382 containing elements in fecal streptococcal strains from veal calves. Antimicrob. Agents Chemother. 47: 2579-2583.

Simonsen GS, Smabrekke L, Monnet DL, Sorensen TL, Moller JK, Kristinsson KG, Lagerqvist-Widh A, Torell E, Digranes A, Harthug S, Sundsfjord A. 2003. Prevalence of resistance to ampicillin, gentamicin and vancomycin in Enterococcus faecalis and Enterococcus faecium isolates from clinical specimens and use of antimicrobials in five Nordic hospitals. J. Antimicrob Chemother. 51:323-31.

Abstract (project related; since 2004)

“Tnvamp – an integrative and conjugative element (ICE) in Enterococcus faecium”. The Norwegian Biochemical Society 41st Contact Meeting. Tromsø, Norway, January 13-15, 2005.
“Horizontal transfer of housekeeping genes by large chromosomal elements in Enterococcus faecium”.2nd International ASM-FEMS Conference on Enterococci. Helsingør, Denmark, August 28-31, 2005