Related Experiment Video
Updated: Aug 12, 2026
A Rat Model of Compound Acne
Published on: November 1, 2024
Acne-like chronic inflammatory activity of Propionibacterium acnes preparations in an animal model: correlation with
Abstract:
The ability of strains and fractions of killed propionibacteria suspensions to produce chronic rat ear inflammation after intradermal injection of 70-micrograms aliquots was highly correlated with production of splenomegaly in the mouse after i.p. injection of 1.4 mg Propionibacterium acnes strains CN 6134, VPI 0009, ATCC 11828, and UCLA SC and N1 produced a 2- to 3-fold increase in rat ear thickness and a 5- to 7-fold increase in mouse spleen weight 15 days post injection. In contrast P. granulosum CN 5888, P. acnes UCLA 6S and periodated, acetylated, or 12-h cultures of VPI 0009 were inactive or weakly active as stimulators of chronic ear inflammation and splenomegaly. Active strains produced in the rat ear a transepidermal elimination response characterized by follicular encapsulation and the formation of secondary comedones. These effects correlated with persistence of phagocytized bacteria within macrophages. Furthermore, when rats were first immunized and then challenged with active strains of P. acnes, an increased sensitivity to low doses of P. acnes and a chronic exacerbation of inflammation was observed.
Insights
Certain Propionibacterium acnes strains induce chronic inflammation and enlarged spleens in animal models. Bacterial persistence within macrophages is key to these inflammatory responses.
Area of Science:
- Immunology
- Microbiology
- Dermatology
Background:
- Propionibacteria are known to modulate immune responses.
- The specific strains and mechanisms driving inflammation are not fully elucidated.
Purpose of the Study:
- To investigate the correlation between Propionibacterium acnes strains and the induction of chronic inflammation and splenomegaly.
- To identify active P. acnes strains and characterize their inflammatory effects.
Main Methods:
- Intradermal injection of killed propionibacteria suspensions in rats.
- Intraperitoneal injection of P. acnes strains in mice.
- Assessment of rat ear thickness and mouse spleen weight.
- Histopathological examination of rat ear tissue.
Main Results:
- Specific P. acnes strains (CN 6134, VPI 0009, ATCC 11828, UCLA SC, N1) significantly increased rat ear thickness and mouse spleen weight.
- Other strains (P. granulosum CN 5888, P. acnes UCLA 6S) and modified cultures showed minimal activity.
- Active strains induced transepidermal elimination, follicular encapsulation, and secondary comedones in rat ears.
- Bacterial persistence within macrophages correlated with observed inflammatory effects.
- Prior immunization with active P. acnes strains led to heightened sensitivity and exacerbated inflammation upon challenge.
Conclusions:
- The inflammatory potential of P. acnes is strain-dependent.
- Bacterial persistence and macrophage interaction are crucial for P. acnes-induced inflammation.
- These findings provide insights into the pathogenesis of P. acnes-related inflammatory conditions.
