Poster Presentation Australian Society for Microbiology Annual Scientific Meeting 2014

Investigating the interaction of commensal and invasive Haemophilus haemolyticus isolates with human respiratory epithelium (#322)

Janessa Pickering 1 , Amy Prosser 1 , Karli Corscadden 2 , Angela Fuery 2 , Celestine Aho 3 , Andrew Greenhill 4 , Deborah Lehmann 2 , Peter Richmond 1 2 , Ruth Thornton 1 2 , Lea-Ann Kirkham 1 2
  1. School of Paediatrics and Child Health, University of Western Australia, Perth, WA, Australia
  2. Telethon Kid's Institute, Perth, WA, Australia
  3. Papua New Guinea Institute for Medical Research, Goroka, Papua New Guinea
  4. School of Applied Sciences and Engineering, Federation University Gippsland Campus, Gippsland, Victoria, Australia

Haemophilus haemolyticus (Hh) resides in the upper respiratory tract. This species is closely related to nontypeable Haemophilus influenzae (NTHi) and molecular differentiation is required for accurate species identification. While NTHi is associated with otitis media, sinusitis, pneumonia and bacteraemia, Hh is considered a commensal with limited reports of causing disease. We have observed that Hh carriage is lower in populations with high NTHi carriage and disease rates (Australian Aboriginal and Papua New Guinean children). We are developing models to investigate whether Hh can prevent NTHi colonisation and ultimately disease. As part of this process it is important to investigate how Hh interacts with host epithelium.

We compared the ability of 10 clinical Hh isolates (9 nasopharyngeal and 1 blood) and the ATCC strain Hh33390 with 3 NTHi isolates (reference strain 86-028NP, 1 middle ear and 1 nasopharyngeal) to associate with and invade D562 nasopharyngeal and A549 bronchoalveolar epithelial cell lines. Despite inter-strain variability, the nasopharyngeal Hh strains were significantly less able to colonise and invade epithelial cells when compared with NTHi (P<0.001). In contrast, the invasive Hhstrain was indistinguishable from NTHi with high levels of epithelial attachment and invasion. Measurement of extracellular inflammatory cytokines at 3h post-challenge revealed that commensal Hh strains elicited high levels of pro-inflammatory cytokines IL-6 and IL-8 whereas detection of these cytokines was negligible following challenge with NTHi or the invasive Hh strain.

Gut commensals elicit a local inflammatory response to regulate colonisation. This regulation may be occurring with Hh in the respiratory tract and requires further investigation. NTHi can evade host immune responses and it appears that the invasive Hh strain also has this property. Genome sequencing of these strains is underway to determine the genetic requirements for colonisation or disease and to select strains for further assessment in our colonisation models.