Exopolysaccharide Production and Biofilm Formation by Histophilus somni

Abstract

The biofilm matrix of Histophilus somni is a complex architecture that differs substantially in structure between a pathogenic and commensal isolate examined. Overall, most pathogenic isolates produce more biofilm than commensal isolates. A major component of the biofilm is exopolysaccharide (EPS), which is also produced in greater quantity in the pathogenic isolate than in the commensal isolate studied. The EPS is composed of a D-mannan polymer, with occasional galactose residues present on side chains, similar in composition to that of yeast mannan. When grown in the presence of sialic acid, the biofilm EPS becomes sialylated and the amino sugars N-acetylglucosamine and N-acetylgalactosamine can be detected. In vitro biofilm formation follows a typical 4-stage growth curve, characterized by attachment, growth, maturation, and detachment. Following experimental challenge, formation of an H. somni biofilm has been demonstrated in cardiopulmonary tissue, often with Pasteurella multocida cohabitating the biofilm. A recently developed diagnostic test can detect antibodies to the EPS only in animals with systemic disease due to H. somni and is therefore capable of distinguishing between healthy animals colonized with H. somni and animals with systemic disease.

Characterization of Actinobacillus seminis biofilm formation

“…Bacillus subtilis biofilm comprises mainly two components: exopolysaccharides and TasA (Dragos et al 2018). H. somni biofilms contain exopolysaccharides as the major components (Petruzzi and Inzana 2016). In contrast, M. haemolytica biofilms seem to be composed mainly of proteins (Boukahil and Czuprinsky 2015).…”

Evidence of the presence of nucleic acids and β-glucan in the matrix of non-typeable Haemophilus influenzae in vitro biofilms

“…However, cellulose production genes have not been found among the members of Pasteurellaceae ; the present finding of a polysaccharide similar to cellulose in NT Hi biofilms was therefore totally unexpected. It has been shown, however, that Histophilus somni , a relative of H. influenzae , synthesizes an exopolysaccharide composed of a D-mannan polymer and with occasional Gal residues present on side chains during biofilm formation50, although the glycosyltrasferase(s) responsible for its synthesis has not been identified. Aggregatibacter actinomycetemcomitans , another member of Pasteurellaceae, also forms biofilms containing an extracellular homopolymer of N -acetylglucosamine residues in β(1 → 6) linkage that acts as an important virulence factor51.…”

Histophilus somni Survives in Bovine Macrophages by Interfering with Phagosome-Lysosome Fusion but Requires IbpA for Optimal Serum Resistance

“…Virulent strains of H. somni possess a wide variety of physiological properties and mechanisms that enable the bacteria to resist the bactericidal effects of host defenses or to modulate host immune cells. Such mechanisms include phase variation of lipooligosaccharide (LOS), modification of LOS with sialic acid and phosphorylcholine (4), apoptosis of endothelial cells and neutrophils with disruption of intercellular junctions (5), and biofilm formation (6). Furthermore, the bacteria secrete a fibrillar and surface-associated immunoglobulin binding protein (IbpA), the N-terminal region of which is capable of binding immunoglobulins through their Fc component and may also contribute to the adherence of the bacteria to host cells (7).…”