title: Host-derived sialic acid is incorporated into Haemophilus influenzae lipopolysaccharide and is a major virulence factor in experimental otitis media.
abstract: Otitis media, a common and often recurrent bacterial infection of childhood, is a major reason for physician visits and the prescription of antimicrobials. Haemophilus influenzae is the cause of approximately 20% of episodes of bacterial otitis media, but most strains lack the capsule, a factor known to play a critical role in the virulence of strains causing invasive H. influenzae disease. Here we show that in capsule-deficient (nontypeable) strains, sialic acid, a terminal residue of the core sugars of H. influenzae lipopolysaccharide (LPS), is a critical virulence factor in the pathogenesis of experimental otitis media in chinchillas. We used five epidemiologically distinct H. influenzae isolates, representative of the genetic diversity of strains causing otitis media, to inoculate the middle ear of chinchillas. All animals developed acute bacterial otitis media that persisted for up to 3 wk, whereas isogenic sialic acid-deficient mutants (disrupted sialyltransferase or CMP-acetylneuraminic acid synthetase genes) were profoundly attenuated. MS analysis indicated that WT bacteria used to inoculate animals lacked any sialylated LPS glycoforms. In contrast, LPS of ex vivo organisms recovered from chinchilla middle ear exudates was sialylated. We conclude that sialylated LPS glycoforms play a key role in pathogenicity of nontypeable H. influenzae and depend on scavenging the essential precursors from the host during the infection.
authors.affiliation: Maxwell Finland Laboratory for Infectious Diseases, Division of Pediatric Infectious Diseases, Boston University School of Medicine, Boston Medical Center, 774 Albany Street, Boston, MA 02118, USA.
authors.forename: Valérie
authors.initials: V
authors.lastname: Bouchet
authors.forename: Derek W
authors.initials: DW
authors.lastname: Hood
authors.forename: Jianjun
authors.initials: J
authors.lastname: Li
authors.forename: Jean-Robert
authors.initials: JR
authors.lastname: Brisson
authors.forename: Gaynor A
authors.initials: GA
authors.lastname: Randle
authors.forename: Adèle
authors.initials: A
authors.lastname: Martin
authors.forename: Zhong
authors.initials: Z
authors.lastname: Li
authors.forename: Richard
authors.initials: R
authors.lastname: Goldstein
authors.forename: Elke K H
authors.initials: EK
authors.lastname: Schweda
authors.forename: Stephen I
authors.initials: SI
authors.lastname: Pelton
authors.forename: James C
authors.initials: JC
authors.lastname: Richards
authors.forename: E Richard
authors.initials: ER
authors.lastname: Moxon
mesh_terms: D000818:Animals; D001483:Base Sequence; D002240:Carbohydrate Sequence; D002682:Chinchilla; D004269:DNA, Bacterial / Q000235:genetics; D004195:Disease Models, Animal; D006192:Haemophilus Infections / Q000209:etiology* / Q000382:microbiology; D006193:Haemophilus influenzae / Q000235:genetics / Q000378:metabolism* / Q000472:pathogenicity*; D006801:Humans; D008070:Lipopolysaccharides / Q000737:chemistry / Q000378:metabolism* / Q000633:toxicity; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009154:Mutation; D019158:N-Acetylneuraminic Acid / Q000378:metabolism*; D010033:Otitis Media / Q000209:etiology* / Q000382:microbiology; D010802:Phylogeny; D021241:Spectrometry, Mass, Electrospray Ionization; D014774:Virulence
chemical_list: D004269:DNA, Bacterial; D008070:Lipopolysaccharides; D019158:N-Acetylneuraminic Acid