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In vitro inflammatory responses elicited by isolates of Alloiococcus otitidis obtained from children with otitis
Christopher Ashhurst-Smith1, Sharron T Hall, Christine J Burns
11Hunter Area Pathology Service Microbiology, The University of Newcastle, Newcastle, New South Wales, Australia.
Abstract:
Alloiococcus otitidis is usually detected in children with otitis media (OM) by PCR as it is not often detected by routine culture. Our improved method for its isolation obtained A. otitidis from nearly 50% of 78 children with OM with effusion. The role of A. otitidis in pathogenesis of OM is unclear. This study tested two hypothesis: (1) that fresh isolates of A. otitidis would elicit pro-inflammatory cytokines from THP-1 monocytic cells equivalent to those induced by Streptococcus pneumoniae; (2) priming THP-1 cells with interferon-gamma (IFN-γ) a surrogate for virus infection, would enhance pro-inflammatory responses. Recent clinical isolates of A. otitidis, S. pneumoniae (ATCC 49619) and a blood culture isolate of S. pneumoniae (SP2) were used in the assays. Cytokines were quantified by BioRad bead assay and Luminex 200. IFN-γ priming enhanced cytokine responses. S. pneumoniae ATCC 49619 induced lower responses than SP2 for IL-1β, IL-6, TNF-α. A. otitidis LW 27 elicited higher IL-1β and TNF-α responses than either pneumococcal isolate. Small green colony types of A. otitidis induced higher responses than large white colony types for IL-8 and IL-1β. The hypothesis that A. otitidis elicits cytokines observed in middle ear effusions was supported; the need to use recent clinical isolates in studies of pathogenesis was highlighted.
Insights
Alloiococcus otitidis, often found in children with otitis media (OM), can trigger inflammatory responses similar to Streptococcus pneumoniae. Priming immune cells with interferon-gamma (IFN-γ) amplified these cytokine reactions.
Area of Science:
- Microbiology
- Immunology
- Otolaryngology
Background:
- Alloiococcus otitidis is frequently detected in pediatric otitis media (OM) via PCR, but rarely by standard culture.
- Its precise role in OM pathogenesis remains largely undetermined.
- This study aimed to investigate the pro-inflammatory potential of A. otitidis.
Purpose of the Study:
- To determine if fresh isolates of A. otitidis induce pro-inflammatory cytokines comparable to Streptococcus pneumoniae in THP-1 monocytic cells.
- To assess if priming THP-1 cells with interferon-gamma (IFN-γ) enhances these pro-inflammatory responses.
Main Methods:
- Utilized recent clinical isolates of A. otitidis and Streptococcus pneumoniae (ATCC 49619, SP2) for assays.
- Quantified cytokine levels using BioRad bead assay and Luminex 200 technology.
- Employed THP-1 monocytic cells, primed with IFN-γ, to model immune responses.
Main Results:
- IFN-γ priming significantly enhanced overall cytokine production.
- A. otitidis LW 27 elicited higher levels of IL-1β and TNF-α compared to both pneumococcal isolates.
- Specific colony types of A. otitidis (small green) showed increased IL-8 and IL-1β responses over others (large white).
Conclusions:
- The findings support the hypothesis that A. otitidis can elicit cytokines found in middle ear effusions.
- Recent clinical isolates are crucial for accurate pathogenesis studies.
- This research highlights A. otitidis as a potential contributor to otitis media inflammation.
