Modulation of Pasteurella multocida capsular polysaccharide during growth under ironrestricted conditions and in vivo

• Published in: Microbiology (Society for General Microbiology) 1994-02, Vol.140 (2), p.263-270
• Main Authors: Jacques, M, Belanger, M, Diarra, M. S, Dargis, M, Malouin, F
• Format: Article
• Language: English
• ISSN: 1350-0872; 1465-2080
• DOI: 10.1099/13500872-140-2-263

Département de Pathologie et Microbiologic, Faculté de Médecine Vétérinaire, Université de Montréal, C.P. 5000, St-Hyacinthe, Québec, Canada J2S 7C6 Laboratoire et Service d'lnfectiologie, Centre de Recherche du Centre Hospitalier de l'Université Laval, Ste-Foy, Québec, Canada G1V4G2 ABSTRACT Summary: Addition of the iron chelators 2,2-dipyridyl, deferoxamine mesylate or apotransferrin to culture media affected the composition and the morphology of Pasteurella multocida cells. Cells grown under iron-restricted conditions expressed iron-regulated proteins and, in addition, iron deprivation markedly reduced the amount of capsular material covering the cells of P. multocida . The addition of iron neutralized the effect of these chelators on capsule production. Cells of P. multocida grown under iron-restricted conditions were more labelled by gold particles coated with polymyxin which is known to interact with the lipid A-core region of lipopolysaccharides, and showed increased affinity for porcine respiratory tract mucus than cells grown under iron-sufficient conditions. Bacterial cells grown in vivo in peritoneal chambers in rats were also only covered by a thin layer (15-20 nm) of capsular material. Although the capsule is believed to be an important virulence factor, our data indicate that under iron-restricted conditions, such as those encountered in vivo, P. multocida may not be heavily encapsulated. Author for correspondence: M. Jacques. Tel: [phone] ext. 348. Fax: [phone]. Keywords: Pasteurella multocida , capsule, polysaccharide, iron restriction