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International Journal of Microbiology
Volume 2011, Article ID 851946, 10 pages
Research Article

Molecular Detection of Persistent Francisella tularensis Subspecies holarctica in Natural Waters

1Department of CBRN Defence and Security, Swedish Defence Research Agency, 901 82 Umeå, Sweden
2Department of Infectious Diseases, Örebro University Hospital, 701 85 Örebro, Sweden
3National Veterinary Institute, 751 89 Uppsala, Sweden
4Department of Clinical Microbiology, Umeå University, 901 87 Umeå, Sweden

Received 28 May 2010; Accepted 9 July 2010

Academic Editor: Max Teplitski

Copyright © 2011 T. Broman et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


Tularemia, caused by the bacterium Francisella tularensis, where F. tularensis subspecies holarctica has long been the cause of endemic disease in parts of northern Sweden. Despite this, our understanding of the natural life-cycle of the organism is still limited. During three years, we collected surface water samples ( ) and sediment samples ( ) in two areas in Sweden with endemic tularemia. Real-time PCR screening demonstrated the presence of F. tularenis lpnA sequences in 108 (32%) and 48 (20%) of the samples, respectively. The 16S rRNA sequences from those samples all grouped to the species F. tularensis. Analysis of the FtM19InDel region of lpnA-positive samples from selected sampling points confirmed the presence of F. tularensis subspecies holarctica-specific sequences. These sequences were detected in water sampled during both outbreak and nonoutbreak years. Our results indicate that diverse F. tularensis-like organisms, including F. tularensis subsp. holarctica, persist in natural waters and sediments in the investigated areas with endemic tularemia.