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The ModA2 Phasevarion of nontypeable Haemophilus influenzae Regulates Resistance to Oxidative Stress and Killing by Human Neutrophils. Sci Rep 2017 06 09;7(1):3161 PMID: 28600561 PMCID: PMC5466613

Pubmed ID





Nontypeable Haemophilus influenzae (NTHI) is the causative agent of multiple respiratory tract infections. Several human pathogens, including NTHI, possess a novel genetic system, termed the phasevarion, which mediates a rapid and reversible change in the expression of many genes throughout the chromosome. This occurs by phase variation of a single gene (modA) that encodes a DNA methyltransferase and results in two phenotypically distinct subpopulations, ON and OFF. NTHI encounters many pressures within the various microenvironments of its human host as the disease course evolves from one of asymptomatic nasopharyngeal carriage to overt disease. These include oxidative stresses, which are present throughout the respiratory tract. To persist in the human nasopharynx and as a pathogen throughout the airways, NTHI must be able to mitigate toxic levels of oxidative stress. Here we show that expression of ModA2, modA2 ON status, resulted in increased sensitivity to oxidative stress. Furthermore, the modA2 ON status resulted in decreased resistance to neutrophil-mediated killing, which resulted in selection for the modA2 OFF subpopulation in an ex vivo survival assay. These findings highlight the importance of the ModA2 phasevarion in adaptation to innate host defences and reveal an additional microenvironmental pressure that selected for a specific ModA2 subpopulation.

Author List

Brockman KL, Branstool MT, Atack JM, Robledo-Avila F, Partida-Sanchez S, Jennings MP, Bakaletz LO


Kenneth Brockman PhD Assistant Professor in the Microbiology and Immunology department at Medical College of Wisconsin


2-s2.0-85020676207   6 Citations

MESH terms used to index this publication - Major topics in bold

Chromosomes, Bacterial
DNA (Cytosine-5-)-Methyltransferases
Gene Expression Regulation, Bacterial
Haemophilus Infections
Haemophilus influenzae
Host-Pathogen Interactions
Microbial Viability
Oxidative Stress
Primary Cell Culture
Reactive Oxygen Species
jenkins-FCD Prod-353 9ccd8489072cb19f5b9f808bb23ed672c582f41e