Acute otitis media results from a complex interplay of host defenses, environmental factors, and virulence characteristics of bacteria. Previous studies suggest that non-typeable Haemophilus influenza (NTHi), an important cause of acute otitis media in children, possess unique genes important in the pathogenesis of this infection. In this project, we will identify potential NTHi factors associated with otitis media using an epidemiologic approach that takes advantage of natural biologic selection. Because NTHi isolated from the middle ears of children with otitis media appear to possess specific genes offering increased bacterial fitness in the middle ear that are not required for NTHi colonization of the pharynx, we will use prevalence analysis, as performed on a whole bacterial genomic DNA microarray, to identify NTHi genes retained by otitis media strains compared to NTHi commensal strains in the pharynges of children.
The Specific Aims of this project are to: I. Identify potential NTHi otitis media-associated genes by prevalence analysis, focusing on known Hi virulence genes, genes identified through in silico subtraction analysis of middle ear and throat strains, and genes within Hi genetic island 7. II. Identify polymorphisms in NTHi virulence genes that predict otitis media by testing the prevalences of the major gene alleles among ear and throat strains. III. Investigate the role of iron metabolism genes in NTHi otitis media by prevalence analysis and by exploration of the function of these genes in iron dependent NTHi growth and in NTHi iron acquisition. IV. Identify by classification tree analysis otitis media pathotypes consisting of clusters of NTHi genes that discriminate acute otitis media strains from throat strains. V. Test for virulence of NTHi lacking otitis media-associated genes in a chinchilla model as proof-of- principle that the gene discovery strategy identifies otitis media virulence genes. Identification of unique NTHi otitis media-associated factors and virulence pathways will facilitate the development of novel approaches to the prevention and treatment of NTHi otitis media that may preserve the unique ecology of NTHi in the pharynges.

Public Health Relevance

The results of this gene discovery project will identify NTHi genes that are more prevalent among otitis media NTHi strains than among commensal throat strains, and thus likely to be important in NTHi survival in the middle ear and to be associated with the disease otitis media. Proteins encoded by these genes will be attractive candidates for a multi-component NTHi vaccine, as targeting otitis media-associated antigens would be expected to reduce otitis media without greatly disturbing the ecology of NTHi in the pharynx.

Agency
National Institute of Health (NIH)
Institute
National Institute on Deafness and Other Communication Disorders (NIDCD)
Type
Research Project (R01)
Project #
5R01DC005840-07
Application #
7619008
Study Section
Clinical Research and Field Studies of Infectious Diseases Study Section (CRFS)
Program Officer
Watson, Bracie
Project Start
2002-09-20
Project End
2011-05-31
Budget Start
2009-06-01
Budget End
2010-05-31
Support Year
7
Fiscal Year
2009
Total Cost
$409,350
Indirect Cost
Name
University of Michigan Ann Arbor
Department
Pediatrics
Type
Schools of Medicine
DUNS #
073133571
City
Ann Arbor
State
MI
Country
United States
Zip Code
48109
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LaCross, Nathan C; Marrs, Carl F; Gilsdorf, Janet R (2014) Otitis media associated polymorphisms in the hemin receptor HemR of nontypeable Haemophilus influenzae. Infect Genet Evol 26:47-57
Davis, Gregg S; Patel, May; Hammond, James et al. (2014) Prevalence, distribution, and sequence diversity of hmwA among commensal and otitis media non-typeable Haemophilus influenzae. Infect Genet Evol 28:223-32
Zhang, Lixin; Patel, Mayuri; Xie, Jingping et al. (2013) Urease operon and urease activity in commensal and disease-causing nontypeable Haemophilus influenzae. J Clin Microbiol 51:653-5
LaCross, Nathan C; Marrs, Carl F; Gilsdorf, Janet R (2013) Population structure in nontypeable Haemophilus influenzae. Infect Genet Evol 14:125-36
Zhang, Lixin; Xie, Jingping; Patel, Mayuri et al. (2012) Nontypeable Haemophilus influenzae genetic islands associated with chronic pulmonary infection. PLoS One 7:e44730
Davis, Gregg S; Sandstedt, Sara A; Patel, Mayuri et al. (2011) Use of bexB to detect the capsule locus in Haemophilus influenzae. J Clin Microbiol 49:2594-601
Nakamura, Shigeki; Shchepetov, Mikhail; Dalia, Ankur B et al. (2011) Molecular basis of increased serum resistance among pulmonary isolates of non-typeable Haemophilus influenzae. PLoS Pathog 7:e1001247
McCrea, Kirk W; Wang, Myron L; Xie, Jingping et al. (2010) Prevalence of the sodC gene in nontypeable Haemophilus influenzae and Haemophilus haemolyticus by microarray-based hybridization. J Clin Microbiol 48:714-9
Sandstedt, Sara A; Marrs, Carl F; Patel, Mayuri et al. (2010) Prevalence of Haemophilus influenzae type b genetic islands among clinical and commensal H. influenzae and H. haemolyticus isolates. J Clin Microbiol 48:2565-8

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