Reduced severity of middle ear infection caused by nontypeable Haemophilus influenzae lacking the hemoglobin/hemoglobin–haptoglobin binding proteins (Hgp) in a chinchilla model of otitis media

• Published in: Microbial pathogenesis Vol. 36; no. 1; pp. 25 - 33
• Main Authors: Morton, Daniel J, Bakaletz, Lauren O, Jurcisek, Joseph A, VanWagoner, Timothy M, Seale, Thomas W, Whitby, Paul W, Stull, Terrence L
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier India Pvt Ltd 2004; Elsevier
• Subjects: Animals; Bacterial Proteins - genetics; Bacterial Proteins - metabolism; Bacteriology; Biological and medical sciences; Carrier Proteins - genetics; Carrier Proteins - metabolism; Chinchilla; Chinchilla model; Fundamental and applied biological sciences. Psychology; Genes, Bacterial; Haemophilus Infections - etiology; Haemophilus Infections - metabolism; Haemophilus Infections - microbiology; Haemophilus influenzae; Haemophilus influenzae - genetics; Haemophilus influenzae - growth & development; Haemophilus influenzae - metabolism; Haptoglobins - metabolism; Heme; Hemoglobins - metabolism; Hemoglobin–haptoglobin; Microbiology; Miscellaneous; Mutation; Otitis media; Otitis Media - etiology; Otitis Media - metabolism; Otitis Media - microbiology; Pathogenesis; Chinchilla model; Hemoglobin–haptoglobin; Otitis media; Pathogenesis; Haemophilus influenzae; Heme; Microbiology; Middle ear disease; Rodentia; Chinchilla; Pasteurellaceae; Binding protein; Vertebrata; Mammalia; Haptoglobin; Hemoglobin; Bacteria; ENT disease; Models
• ISSN: 0882-4010; 1096-1208
• DOI: 10.1016/j.micpath.2003.08.007

Since Haemophilus influenzae lacks enzymes necessary for synthesis of the porphyrin ring, it has an absolute growth requirement for a porphyrin source. This requirement can be satisfied in vitro by hemoglobin and hemoglobin complexed to haptoglobin. The products of the hgp genes mediate the utilization of heme from hemoglobin–haptoglobin. These genes are also involved in the use of heme from hemoglobin, although additional gene products independently mediate the acquisition of heme from this substrate. Different strains of H. influenzae possess one to four hgp genes. A nontypeable H. influenzae mutant lacking all the hgp genes was constructed and compared to the wild-type strain in a chinchilla ( Chinchilla lanigera) model of otitis media. Compared to the wild-type strain, the hgp-deficient mutant exhibited a significantly delayed onset of detectable middle ear infection and significantly reduced duration of infection as assessed by both video otoscopy and tympanometry and as evidenced by viable bacterial counts in middle ear effusions. In addition, the maximum bacterial load in the middle ears of chinchillas infected with the mutant strain was significantly reduced when compared to the parent. These data indicate that the hemoglobin/hemoglobin–haptoglobin binding proteins are required for bacterial proliferation during H. influenzae-induced otitis media in chinchillas.