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© Research
Publication : International journal of medical microbiology : IJMM

Serum resistance and phase variation of a nasopharyngeal non-typeable Haemophilus influenzae isolate.

Scientific Fields
Diseases
Organisms
Applications
Technique

Published in International journal of medical microbiology : IJMM - 01 Feb 2017

Lichtenegger S, Bina I, Durakovic S, Glaser P, Tutz S, Schild S, Reidl J,

Link to Pubmed [PMID] – 28179078

Link to DOI – S1438-4221(16)30175-810.1016/j.ijmm.2017.01.005

Int J Med Microbiol 2017 Feb; 307(2): 139-146

Haemophilus influenzae harbours a complex array of factors to resist human complement attack. As non-typeable H. influenzae (NTHi) strains do not possess a capsule, their serum resistance mainly depends on other mechanisms including LOS decoration. In this report, we describe the identification of a highly serum resistant, nasopharyngeal isolate (NTHi23) by screening a collection of 77 clinical isolates. For NTHi23, we defined the MLST sequence type 1133, which matches the profile of a previously published invasive NTHi isolate. A detailed genetic analysis revealed that NTHi23 shares several complement evading mechanisms with invasive disease isolates. These mechanisms include the functional expression of a retrograde phospholipid trafficking system and the presumable decoration of the LOS structure with sialic acid. By screening the NTHi23 population for spontaneous decreased serum resistance, we identified a clone, which was about 103-fold more sensitive to complement-mediated killing. Genome-wide analysis of this isolate revealed a phase variation in the N’-terminal region of lpsA, leading to a truncated version of the glycosyltransferase (LpsA). We further showed that a NTHi23 lpsA mutant exhibits a decreased invasion rate into human alveolar basal epithelial cells. Since only a small proportion of the NTHi23 population expressed the serum sensitive phenotype, resulting from lpsA phase-off, we conclude that the nasopharyngeal environment selected for a population expressing the intact and functional glycosyltransferase.

https://pubmed.ncbi.nlm.nih.gov/28179078