The ecology of nasal colonization of Streptococcus pneumoniae, Haemophilus influenzae and Staphylococcus aureus: the role of competition and interactions with host's immune response

Margolis, E., Yates, A. and Levin, B. R. (2010) The ecology of nasal colonization of Streptococcus pneumoniae, Haemophilus influenzae and Staphylococcus aureus: the role of competition and interactions with host's immune response. BMC Microbiology, 10, p. 59. (doi: 10.1186/1471-2180-10-59)

Abstract

<b>Background</b> The first step in invasive disease caused by the normally commensal bacteria <i>Streptococcus pneumoniae, Staphylococcus aureus</i> and <i>Haemophilus influenzae</i> is their colonization of the nasal passages. For any population to colonize a new habitat it is necessary for it to be able to compete with the existing organisms and evade predation. In the case of colonization of these species the competition is between strains of the same and different species of bacteria and the predation is mediated by the host's immune response. Here, we use a neonatal rat model to explore these elements of the ecology of nasal colonization by these occasionally invasive bacteria.<p></p> <b>Results</b> When neonatal rats are colonized by any one of these species the density of bacteria in the nasal passage rapidly reaches a steady-state density that is species-specific but independent of inoculum size. When novel populations of <i>H. influenzae</i> and <i>S. pneumoniae</i> are introduced into the nasal passages of neonatal rats with established populations of the same species, residents and invaders coexisted. However, this was not the case for <i>S. aureus</i> - the established population inhibited invasion of new <i>S. aureus</i> populations. In mixed-species introductions, <i>S. aureus</i> or <i>S. pneumoniae</i> facilitated the invasion of another <i>H. influenzae</i> population; for other pairs the interaction was antagonistic and immune-mediated. For example, under some conditions <i>H. influenzae</i> promoted an immune response which limited the invasion of <i>S. pneumoniae</i> .<p></p> <b>Conclusions</b> Nasal colonization is a dynamic process with turnover of new strains and new species. These results suggest that multiple strains of either <i>H. influenzae</i> or <i>S. pneumoniae</i> can coexist; in contrast, <i>S. aureus</i> strains require a host to have no other <i>S. aureus</i> present to colonize. Levels of colonization (and hence the possible risk of invasive disease) by <i>H. influenzae</i> are increased in hosts pre-colonized with either <i>S. aureus</i> or <i>S. pneumoniae</i> .<p></p>

• Item Type: Articles
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: Yates, Professor Andrew
• Authors: Margolis, E., Yates, A., and Levin, B. R.
• College/School: College of Medical Veterinary and Life Sciences > School of Infection & Immunity
• Journal Name: BMC Microbiology
• Publisher: BioMed Central Ltd.
• ISSN: 1471-2180
• Copyright Holders: Copyright © 2010 The Authors
• First Published: First published in BMC Microbiology 10:59
• Publisher Policy: Reproduced under a Creative Commons License