Phosphorylcholine Decreases Early Inflammation and Promotes the Establishment of Stable Biofilm Communities of Nontypeable Haemophilus influenzae Strain 86-028NP in a Chinchilla Model of Otitis Media

Abstract

Haemophilus influenzae is a gram-negative pleiomorphic bacterium that is a common commensal/mutualist within the human airways (30). Encapsulated H. influenzae strains are overt pathogens causing invasive disease (3) and have largely been contained by a vaccine effective against the predominant capsular serotype b strains (32). In contrast, the so-called nontypeable H. influenzae (NTHi) strains lacking capsular polysaccharides remain predominant in asymptomatic carriage and localized airway infections (14, 29). These infections are mostly opportunistic in nature and include bronchiopneumonia, sinusitis, and otitis media (OM). OM is among the most common pediatric infections, causing an estimated ϳ$5 billion in costs of treatment and parents' missed work days per year (20). OM infections include chronic OM that is difficult to resolve with antibiotic therapy, and it has long been postulated that chronic OM involves the formation of bacterial biofilm communities (5, 35). In support of that hypothesis, biofilms have been visualized in tympanostomy drain tubes removed from patients with OM and on middle ear tissue from experimentally infected chinchillas (7,18,33). More recent evidence shows that NTHi and other bacterial agents are present within biofilms on tissue specimens obtained from patients with chronic and recurrent OM (13).The H. influenzae surface is covered with lipooligosaccharide (LOS) endotoxins that lack a repeating O side chain. Instead, the H. influenzae LOS features a diverse collection of LOS glycoforms that differ in the length, content, and nature of the chemical linkages found in the oligosaccharide portion. These LOS oligosaccharides include structures that are antigenically similar to host cell-surface glycolipids and may also contain the host membrane constituents sialic acid (NeuAc) and phosphorylcholine (PCho) (41). LOS confers resistance to host killing (8,9,37) and is also the primary target of the Toll-like receptor 4 pathway that mediates protection against H. influenzae in the airways (47). It has been established that NTHi strains that express NeuAc-LOS forms comprise a greater proportion of biofilm communities than of planktonic cultures, and that mutations eliminating these forms decrease biofilm formation and bacterial persistence in animal models of OM (4,12,18,43). More recently, we showed that LOS purified from biofilms has decreased potency as an inflammatory agonist, which correlated with an increase in PCho ϩ LOS forms that were present within biofilms (55). In this study, we compared the virulence

Decoration ofPasteurella multocidaLipopolysaccharide with Phosphocholine Is Important for Virulence

“…In H. influenzae, PCho is found on LPS and has been shown to be important for colonization and persistence at the mucosal surface (15,38). Conversely, PCho decoration of LPS has also been shown to increase susceptibility to complement-mediated killing in serum by the direct binding of C-reactive protein to PCho (9,21,38).…”

Adenoid Reservoir for Pathogenic Biofilm Bacteria

“…3D structures encased in an extracellular matrix and associated with the epithelia indicate that a carbohydrate matrix bound by the lectin probes is produced by bacteria. Although the biofilm matrix is structurally complex (29,34,36), demonstration of the matrix with carbohydrate probes gave the most unambiguous results of intracellular biofilms. Furthermore, ex vivo incubation of the adenoid epithelium with antibiotics demonstrated that biofilm bacteria were recalcitrant to antibiotic killing.…”

Comprehensive Proteomic and Metabolomic Signatures of Nontypeable Haemophilus influenzae-Induced Acute Otitis Media Reveal Bacterial Aerobic Respiration in an Immunosuppressed Environment

“…ChoP modification is important for NTHI colonization and persistence in AOM because of roles in biofilm formation, adherence to cells through the PAF receptor, survival of complement-mediated lysis, as well as resistance to antimicrobial peptides (121)(122)(123)(124)(125)(126)(127). The significant reduction of PC derivatives could be because of decreases in biosynthesis or use as a preferential substrate for glycan modification by NTHI.…”