Genotypic and phenotypic diversity of the noncapsulated Haemophilus influenzae: Adaptation and pathogenesis in the human airways

Junkal Garmendia, Pau Martí-Lliteras, Javier Moleres, Carmen Puig, Jose A. Bengoechea

Research output: Contribution to journalArticlepeer-review

20 Citations (Scopus)


The human respiratory tract contains a highly adapted microbiota including commensal and opportunistic pathogens. Noncapsulated or nontypable Haemophilus influenzae (NTHi) is a human-restricted member of the normal airway microbiota in healthy carriers and an opportunistic pathogen in immunocompromised individuals. The duality of NTHi as a colonizer and as a symptomatic infectious agent is closely related to its adaptation to the host, which in turn greatly relies on the genetic plasticity of the bacterium and is facilitated by its condition as a natural competent. The variable genotype of NTHi accounts for its heterogeneous gene expression and variable phenotype, leading to differential host-pathogen interplay among isolates. Here we review our current knowledge of NTHi diversity in terms of genotype, gene expression, antigenic variation, and the phenotypes associated with colonization and pathogenesis. The potential benefits of NTHi diversity studies discussed herein include the unraveling of pathogenicity clues, the generation of tools to predict virulence from genomic data, and the exploitation of a unique natural system for the continuous monitoring of long-term bacterial evolution in human airways exposed to noxious agents. Finally, we highlight the challenge of monitoring both the pathogen and the host in longitudinal studies, and of applying comparative genomics to clarify the meaning of the vast NTHi genetic diversity and its translation to virulence phenotypes.
Original languageEnglish
Pages (from-to)157-170
JournalInternational Microbiology
Issue number4
Publication statusPublished - Dec 2012

Bibliographical note

Copyright 2013 Elsevier B.V., All rights reserved.


  • Adaptation, Biological
  • Antigenic Variation
  • Gene Expression
  • Genetic Variation
  • Genotype
  • Haemophilus Infections
  • Haemophilus influenzae
  • Humans
  • Phenotype
  • Respiratory System
  • Respiratory Tract Infections
  • Virulence


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