Poster Presentation Australian Society for Microbiology Annual Scientific Meeting 2013

The Multispecies H. influenzae/ S. pneumoniae Biofilm as a Stress Response and Means of Successful Colonization (#335)

Alexandra Tikhomirova 1 , Stephen Kidd 1
  1. University of Adelaide, Adelaide, SA, Australia

Streptococcus pneumoniae and Haemophilus influenzae are commensal bacteria that inhabit the human nasopharynx. Both species can migrate from this anatomical niche and in doing so, cause various diseases. Both S. pneumoniae and H. influenzae were present in middle ear tissues of chronic OM patients1. However, the study of the interplay between these pathogens is a  recent field of study, and there is controversy in the current literature about the patterns of competition or cooperation between these pathogens2,3,4,5 . This study investigates the interactions between H. influenzae and S. pneumoniae in both the planktonic and biofilm state in co-culture conditions. To date, we have determined that S. pneumoniae is able to predominate over H. influenzae in both the planktonic and biofilm state in co-culture growth studies, dramatically reducing H. influenzae viability. This effect held true for the laboratory strains and various clinical isolates of both species. These initial experiments were in batch culture and the competitive interaction was observed to occur after 24hrs in co-culture, but not after 6hrs, suggesting the competitive effect is time-specific or growth phase dependent. No extracellular component of S. pneumoniae seemed to be the damaging agent; it was not a bacteriocin or hydrogen peroxide derived from S. pneumoniae6 . The effect of pH however was shown to be important in these competitive interactions; the competitive advantage of S. pneumonaie was not observed at an alkaline pH (pH 8.0), but did occur at neutral (pH 7.4) or acidic pH (pH 6.8). An important aspect of this study is to analyse the gene expression patterns occurring between these pathogens that allow for them to co-exist. We also aim to determine the molecular pathways that vary under changes in pH and thereby alter the interaction between these bacteria. These aspects of the study will provide a systems perspective of the molecular pathways that enable these pathogens to co-exist under select conditions.

  1. Hall-Stoodley L, H.F.G.A. and et al. (2006) DIrect detection of bacterial biofilms on the middle-ear mucosa of children with chronic otitis media. JAMA: The Journal of the American Medical Association 296, 202-211
  2. Lysenko, E.S., et al. (2005) The Role of Innate Immune Responses in the Outcome of Interspecies Competition for Colonization of Mucosal Surfaces. PLoS Pathog 1, e1
  3. Margolis, E., et al. (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, 59
  4. Weimer, K.E.D., et al. (2010) Coinfection with Haemophilus influenzae Promotes Pneumococcal Biofilm Formation during Experimental Otitis Media and Impedes the Progression of Pneumococcal Disease. Journal of Infectious Diseases 202, 1068-1075
  5. Cope, E.K., et al. (2011) Regulation of Virulence Gene Expression Resulting from Streptococcus pneumoniae and Nontypeable Haemophilus influenzae Interactions in Chronic Disease. PLoS ONE 6, e28523
  6. Pericone, C.D., et al. (2000) Inhibitory and Bactericidal Effects of Hydrogen Peroxide Production by Streptococcus pneumoniae on Other Inhabitants of the Upper Respiratory Tract. Infection and Immunity 68, 3990-3997