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Journal of Bacteriology, November 2007, p. 8179-8185, Vol. 189, No. 22
0021-9193/07/$08.00+0     doi:10.1128/JB.00479-07
Copyright © 2007, American Society for Microbiology. All Rights Reserved.

Characterization and Comparison of Biofilm Development by Pathogenic and Commensal Isolates of Histophilus somni{triangledown}

Indra Sandal,1 Wenzhou Hong,2 W. Edward Swords,2 and Thomas J. Inzana1*

Center for Molecular Medicine and Infectious Diseases, Virginia-Maryland Regional College of Veterinary Medicine, Virginia Polytechnic Institute and State University, Blacksburg, Virginia,1 Department of Microbiology and Immunology, Wake Forest University Health Sciences, Winston-Salem, North Carolina2

Received 29 March 2007/ Accepted 12 July 2007

Histophilus somni (Haemophilus somnus) is an obligate inhabitant of the mucosal surfaces of bovines and sheep and an opportunistic pathogen responsible for respiratory disease, meningoencephalitis, myocarditis, arthritis, and other systemic infections. The identification of an exopolysaccharide produced by H. somni prompted us to evaluate whether the bacterium was capable of forming a biofilm. After growth in polyvinyl chloride wells a biofilm was formed by all strains examined, although most isolates from systemic sites produced more biofilm than commensal isolates from the prepuce. Biofilms of pneumonia isolate strain 2336 and commensal isolate strain 129Pt were grown in flow cells, followed by analysis by confocal laser scanning microscopy and scanning electron microscopy. Both strains formed biofilms that went through stages of attachment, growth, maturation, and detachment. However, strain 2336 produced a mature biofilm that consisted of thick, homogenous mound-shaped microcolonies encased in an amorphous extracellular matrix with profound water channels. In contrast, strain 129Pt formed a biofilm of cell clusters that were tower-shaped or distinct filamentous structures intertwined with each other by strands of extracellular matrix. The biofilm of strain 2336 had a mass and thickness that was 5- to 10-fold greater than that of strain 129Pt and covered 75 to 82% of the surface area, whereas the biofilm of strain 129Pt covered 35 to 40% of the surface area. Since H. somni is an obligate inhabitant of the bovine and ovine host, the formation of a biofilm may be crucial to its persistence in vivo, and our in vitro evidence suggests that formation of a more robust biofilm may provide a selective advantage for strains that cause systemic disease.

* Corresponding author. Mailing address: Center for Molecular Medicine and Infectious Diseases, Virginia-Maryland Regional College of Veterinary Medicine, Virginia Polytechnic Institute and State University, 1800 Kraft Dr., Suite 200, Blacksburg, VA 24061. Phone: (540) 231-4692. Fax: (540) 231-5553. E-mail: tinzana{at}vt.edu

{triangledown} Published ahead of print on 20 July 2007.

Journal of Bacteriology, November 2007, p. 8179-8185, Vol. 189, No. 22
0021-9193/07/$08.00+0     doi:10.1128/JB.00479-07
Copyright © 2007, American Society for Microbiology. All Rights Reserved.





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