title: Biofilm formation by virulent and non-virulent strains of Haemophilus parasuis.
abstract: Haemophilus parasuis is a commensal bacterium of the upper respiratory tract of healthy pigs. It is also the etiological agent of Glässer's disease, a systemic disease characterized by polyarthritis, fibrinous polyserositis and meningitis, which causes high morbidity and mortality in piglets. The aim of this study was to evaluate biofilm formation by well-characterized virulent and non-virulent strains of H. parasuis. We observed that non-virulent strains isolated from the nasal cavities of healthy pigs formed significantly (p < 0.05) more biofilms than virulent strains isolated from lesions of pigs with Glässer's disease. These differences were observed when biofilms were formed in microtiter plates under static conditions or formed in the presence of shear force in a drip-flow apparatus or a microfluidic system. Confocal laser scanning microscopy using different fluorescent probes on a representative subset of strains indicated that the biofilm matrix contains poly-N-acetylglucosamine, proteins and eDNA. The biofilm matrix was highly sensitive to degradation by proteinase K. Comparison of transcriptional profiles of biofilm and planktonic cells of the non-virulent H. parasuis F9 strain revealed a significant number of up-regulated membrane-related genes in biofilms, and genes previously identified in Actinobacillus pleuropneumoniae biofilms. Our data indicate that non-virulent strains of H. parasuis have the ability to form robust biofilms in contrast to virulent, systemic strains. Biofilm formation might therefore allow the non-virulent strains to colonize and persist in the upper respiratory tract of pigs. Conversely, the planktonic state of the virulent strains might allow them to disseminate within the host.
authors.forename: Bernardo
authors.initials: B
authors.lastname: Bello-Ortí
authors.forename: Vincent
authors.initials: V
authors.lastname: Deslandes
authors.forename: Yannick D N
authors.initials: YD
authors.lastname: Tremblay
authors.forename: Josée
authors.initials: J
authors.lastname: Labrie
authors.forename: Kate J
authors.initials: KJ
authors.lastname: Howell
authors.forename: Alexander W
authors.initials: AW
authors.lastname: Tucker
authors.forename: Duncan J
authors.initials: DJ
authors.lastname: Maskell
authors.forename: Virginia
authors.initials: V
authors.lastname: Aragon
authors.affiliation: Groupe de recherche sur les maladies infectieuses du porc, Faculté de médecine vétérinaire, Université de Montréal, St-Hyacinthe, Québec J2S 7C6, Canada. mario.jacques@umontreal.ca.
authors.forename: Mario
authors.initials: M
authors.lastname: Jacques
mesh_terms: D000818:Animals; D018441:Biofilms / Q000254:growth & development*; D006192:Haemophilus Infections / Q000382:microbiology / Q000662:veterinary*; D044137:Haemophilus parasuis / Q000235:genetics / Q000254:growth & development / Q000472:pathogenicity* / Q000502:physiology*; D018613:Microscopy, Confocal / Q000662:veterinary; D008969:Molecular Sequence Data; D017422:Sequence Analysis, DNA / Q000662:veterinary; D013552:Swine; D013553:Swine Diseases / Q000382:microbiology*; D014132:Trachea / Q000382:microbiology*; D014774:Virulence