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Infection and Immunity, August 2006, p. 4809-4816, Vol. 74, No. 8
0019-9567/06/$08.00+0     doi:10.1128/IAI.00034-06
Copyright © 2006, American Society for Microbiology. All Rights Reserved.

Virulence of Francisella spp. in Chicken Embryos

Eli B. Nix,1 Karen K. M. Cheung,1 Diana Wang,2 Na Zhang,1 Robert D. Burke,1,2 and Francis E. Nano1*

Department of Biochemistry and Microbiology,1 Department of Biology, University of Victoria, Victoria, British Columbia, Canada2

Received 6 January 2006/ Returned for modification 7 February 2006/ Accepted 9 May 2006

We examined the utility of infecting chicken embryos as a means of evaluating the virulence of different Francisella sp. strains and mutants. Infection of 7-day-old chicken embryos with a low dose of F. novicida or F. tularensis subsp. holarctica live vaccine strain (LVS) resulted in sustained growth for 6 days. Different doses of these two organisms were used to inoculate chicken embryos to determine the time to death. These experiments showed that wild-type F. novicida was at least 10,000-fold more virulent than the LVS strain. We also examined the virulence of several attenuated mutants of F. novicida, and they were found to have a wide range of virulence in chicken embryos. Fluorescent microscopic examination of infected chicken embryo organs revealed that F. tularensis grew in scattered foci of infections, and in all cases the F. tularensis appeared to be growing intracellularly. These results demonstrate that infection of 7-day-old chicken embryos can be used to evaluate the virulence of attenuated F. tularensis strains.

* Corresponding author. Mailing address: Department of Biochemistry and Microbiology, PO Box 3055 STN CSC, University of Victoria, Victoria, B.C. V8W 3P6, Canada. Phone: (250) 721-7074. Fax: (250) 721-8855. E-mail: fnano{at}uvic.ca.

Editor: D. L. Burns

Infection and Immunity, August 2006, p. 4809-4816, Vol. 74, No. 8
0019-9567/06/$08.00+0     doi:10.1128/IAI.00034-06
Copyright © 2006, American Society for Microbiology. All Rights Reserved.



This article has been cited by other articles:

  • Schmerk, C. L., Duplantis, B. N., Wang, D., Burke, R. D., Chou, A. Y., Elkins, K. L., Ludu, J. S., Nano, F. E. (2009). Characterization of the pathogenicity island protein PdpA and its role in the virulence of Francisella novicida. Microbiology 155: 1489-1497 [Abstract] [Full Text]  
  • Ludu, J. S., de Bruin, O. M., Duplantis, B. N., Schmerk, C. L., Chou, A. Y., Elkins, K. L., Nano, F. E. (2008). The Francisella Pathogenicity Island Protein PdpD Is Required for Full Virulence and Associates with Homologues of the Type VI Secretion System. J. Bacteriol. 190: 4584-4595 [Abstract] [Full Text]  


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