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Infect Immun. 2016 Jan 4;84(3):765-74. doi: 10.1128/IAI.01185-15.

Comparative Analyses of the Lipooligosaccharides from Nontypeable Haemophilus influenzae and Haemophilus haemolyticus Show Differences in Sialic Acid and Phosphorylcholine Modifications.

Author information

1
Buck Institute for Research on Aging, Novato, California, USA.
2
Department of Microbiology, The University of Iowa, Iowa City, Iowa, USA.
3
The Center for Microbial Pathogenesis at the Research Institute at Nationwide Children's Hospital and the Center for Microbial Interface Biology and Department of Pediatrics, The Ohio State University, Columbus, Ohio, USA.
4
Bioinformatics Facility, The University of Iowa, Iowa City, Iowa, USA.
5
Department of Medicine, University at Buffalo, State University of New York, Buffalo, New York, USA.
6
Department of Biostatistics, College of Public Health, The University of Iowa, Iowa City, Iowa, USA.
7
Buck Institute for Research on Aging, Novato, California, USA Department of Pharmaceutical Chemistry, University of California, San Francisco, San Francisco, California, USA.
8
Department of Microbiology, The University of Iowa, Iowa City, Iowa, USA michael-apicella@uiowa.edu.

Abstract

Haemophilus haemolyticus and nontypeable Haemophilus influenzae (NTHi) are closely related upper airway commensal bacteria that are difficult to distinguish phenotypically. NTHi causes upper and lower airway tract infections in individuals with compromised airways, while H. haemolyticus rarely causes such infections. The lipooligosaccharide (LOS) is an outer membrane component of both species and plays a role in NTHi pathogenesis. In this study, comparative analyses of the LOS structures and corresponding biosynthesis genes were performed. Mass spectrometric and immunochemical analyses showed that NTHi LOS contained terminal sialic acid more frequently and to a higher extent than H. haemolyticus LOS did. Genomic analyses of 10 strains demonstrated that H. haemolyticus lacked the sialyltransferase genes lic3A and lic3B (9/10) and siaA (10/10), but all strains contained the sialic acid uptake genes siaP and siaT (10/10). However, isothermal titration calorimetry analyses of SiaP from two H. haemolyticus strains showed a 3.4- to 7.3-fold lower affinity for sialic acid compared to that of NTHi SiaP. Additionally, mass spectrometric and immunochemical analyses showed that the LOS from H. haemolyticus contained phosphorylcholine (ChoP) less frequently than the LOS from NTHi strains. These differences observed in the levels of sialic acid and ChoP incorporation in the LOS structures from H. haemolyticus and NTHi may explain some of the differences in their propensities to cause disease.

PMID:
26729761
PMCID:
PMC4771351
DOI:
10.1128/IAI.01185-15
[Indexed for MEDLINE]
Free PMC Article

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