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Purified streptococcal cell wall (PG-APS) causes experimental otitis media
1Department of Microbiology and Immunology, School of Medicine, East Carolina University, Greenville, NC 27858, USA.
Abstract:
Purified peptidoglycan-polysaccharide from Group A Streptococcus pyogenes cell wall (PG-APS) was prepared under sterile, pyrogen-free conditions and injected percutaneously into the middle ear cavities (MEC) of groups of gerbils. Each group was observed otoscopically at 1, 2, 5, 7, 9, 12 and 14 days. Histologic specimens were obtained from each group at 2, 5, 7, 9 and 14 days. Histologically, PG-APS produced mild, acute inflammation during the first 3 days and mild to moderate inflammation with features of both acute and chronic pathology from days 5 through 9. An early response by plasma cells and macrophages was seen. Most animals had recovered with minor sequelae by day 14. Challenge intraperitoneally with 20 micrograms of PG-APS at 14 days following MEC injection of PG-APS did not exacerbate the middle ear inflammation. Five chinchillas, tested for comparison, responded similarly to PG-APS.
Insights
Group A Streptococcus pyogenes peptidoglycan-polysaccharide (PG-APS) caused mild middle ear inflammation in gerbils, with most recovering within 14 days. Subsequent PG-APS challenge did not worsen inflammation.
Area of Science:
- Microbiology
- Immunology
- Otolaryngology
Background:
- Group A Streptococcus pyogenes is a significant human pathogen.
- Understanding the host response to bacterial components is crucial for developing effective treatments.
Purpose of the Study:
- To investigate the inflammatory response in the middle ear cavity (MEC) to purified peptidoglycan-polysaccharide (PG-APS) from Group A Streptococcus pyogenes.
- To assess the resolution of inflammation and potential for exacerbation upon re-challenge.
Main Methods:
- Sterile, pyrogen-free PG-APS was percutaneously injected into the MEC of gerbils.
- Animals were monitored otoscopically and histologically at various time points (1-14 days).
- A subset of animals received an intraperitoneal PG-APS challenge 14 days post-MEC injection.
Main Results:
- PG-APS induced mild acute inflammation in the early stages (first 3 days).
- Mild to moderate inflammation with acute and chronic features was observed from days 5-9, with plasma cell and macrophage infiltration.
- Most gerbils showed recovery with minor sequelae by day 14.
- Intraperitoneal PG-APS challenge did not exacerbate middle ear inflammation.
Conclusions:
- PG-APS from Group A Streptococcus pyogenes elicits a transient inflammatory response in the gerbil middle ear.
- The middle ear appears to resolve PG-APS-induced inflammation effectively within 14 days.
- The study suggests a limited capacity for immune priming or potentiation of inflammation by PG-APS in this model.