Capsular Polysaccharide Interferes with Biofilm Formation byPasteurella multocidaSerogroup A

Abstract

Pasteurella multocida is an important multihost animal and zoonotic pathogen that is capable of causing respiratory and multisystemic diseases, bacteremia, and bite wound infections. The glycosaminoglycan capsule of P. multocida is an essential virulence factor that protects the bacterium from host defenses. However, chronic infections (such as swine atrophic rhinitis and the carrier state in birds and other animals) may be associated with biofilm formation, which has not been characterized in P. multocida. Biofilm formation by clinical isolates was inversely related to capsule production and was confirmed with capsule-deficient mutants of highly encapsulated strains. Capsule-deficient mutants formed biofilms with a larger biomass that was thicker and smoother than the biofilm of encapsulated strains. Passage of a highly encapsulated, poor-biofilm-forming strain under conditions that favored biofilm formation resulted in the production of less capsular polysaccharide and a more robust biofilm, as did addition of hyaluronidase to the growth medium of all of the strains tested. The matrix material of the biofilm was composed predominately of a glycogen exopolysaccharide (EPS), as determined by gas chromatography-mass spectrometry, nuclear magnetic resonance, and enzymatic digestion. However, a putative glycogen synthesis locus was not differentially regulated when the bacteria were grown as a biofilm or planktonically, as determined by quantitative reverse transcriptase PCR. Therefore, the negatively charged capsule may interfere with biofilm formation by blocking adherence to a surface or by preventing the EPS matrix from encasing large numbers of bacterial cells. This is the first detailed description of biofilm formation and a glycogen EPS by P. multocida.

Lon Protease Has Multifaceted Biological Functions in Acinetobacter baumannii

“…This finding could explain the observations that the lon::FRT cells were unable to form pellicle biofilms but had increased Congo red staining (Fig.1). Evidence for this kind of interplay between an altered cell envelope and biofilm development in bacteria was observed previously (44)(45)(46). For example, increased capsular polysaccharide production in Vibrio vulnificus inhibits biofilm formation by restricting continual biofilm growth (63).…”

Exacerbation of Streptococcus Equi (Strangles) by Overly Nutritious Diets in Horses: A Model for Infectious Bacterial Diseases of Horses and Other Livestock

“…Mucoid polysaccharide (hyaluronic acid) influences the virulence but it may depend on the presence or absence of other factors, like M-protein [10]. An essential virulence factor of Pasturella multocida is a glycosaminoglycan capsular polysaccharide (CPS) that helps protect surface antigens from the host's immune system and prevents phagocytosis and bactericidal activity and interferes with Biofilm formation [11]. Studies with S. equi as a model offer evidence that low-virulence strains of bacteria may revert to highly virulent strains if animals are exposed to overly nutritious diets.…”

“…There are apparently strains of S. equi with different levels of virulence, but all strains are seemingly pathogenic and not part of the normal flora. Unlike S. equi, Pasturella multocida, may be part of the normal flora of the respiratory tract of livestock like swine, cattle and other animals [11] and if animals are on a low plane of nutrition, these bacteria may be innocuous. However, if the plane of nutrition is acutely elevated, Pasturella spp.…”

“…Overly nutritious dietary ingredients enhance the production of CPS which protects bacteria from the immune system and phagocytosis allowing low-virulent bacteria to become highly virulent pathogenic bacteria like S. equi in horses [7]. S. equi infections or strangles in horses may be a model for other infectious bacterial diseases of horses, and diseases in other livestock, like Pasturella multocida [11] in feedlot cattle [12] that are acutely fed overly nutritious diets.…”

A capsular polysaccharide-expressing live vaccine suppresses streptococcal toxic shock-like syndrome and provides sequence type-independent protection during Streptococcus suis infection

“…Encapsulated pathogens like S. suis employ CPS to evade host innate immunity (12). CPS is the first exposed layer to the host and is associated with functions of various bacterial components and with the immunogenicity of vaccine strains (13), implying the importance of CPS expression for vaccines against encapsulated pathogens.…”