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Neurotropic response of Spiroplasma mirum following peripheral inoculation in the rat
F O Bastian1, R A Jennings, C J Hoff
1Department of Pathology, University of South Alabama College of Medicine, Mobile 36617.
Abstract:
Spiroplasma mirum experimentally produces a persistent brain infection in suckling rats when administered intracerebrally. In order to examine spiroplasma infection induced by a more natural route, suckling rats were inoculated both intraperitoneally and subcutaneously with strain GT-48. No mortality was recorded over a 50-day study period. Rats developed localized alopecia and showed a significant reduction in body weight. Minimal pathological alterations were observed in brain tissues, in addition to cataracts, retinal degeneration and panophthalmitis. Spiroplasmas were recovered from brain and spleen on day 2 following peripheral inoculation with highest titres in the spleen. Spleen titres significantly declined (p less than 0.022) during the 50-day study period. On day 50, brain titres exceeded those in the spleen. The attraction of spiroplasma to central nervous system tissues may be related to its nutritional dependence on sterols.
Insights
Spiroplasma mirum infection in rats via peripheral routes caused reduced body weight and eye damage, with spiroplasmas accumulating in the brain over time. This suggests a potential neurotropic pathway for Spiroplasma mirum.
Area of Science:
- Microbiology
- Infectious Diseases
- Neuroscience
Background:
- Spiroplasma mirum is known to cause persistent brain infections in rats after intracerebral administration.
- Understanding infection routes beyond direct brain inoculation is crucial for assessing Spiroplasma mirum's pathogenic potential.
Purpose of the Study:
- To investigate Spiroplasma mirum infection in suckling rats using more natural peripheral inoculation routes (intraperitoneal and subcutaneous).
- To characterize the clinical signs, pathological alterations, and spiroplasma distribution in rats following peripheral inoculation.
Main Methods:
- Suckling rats were inoculated intraperitoneally and subcutaneously with Spiroplasma mirum strain GT-48.
- Animals were monitored for 50 days for mortality, body weight changes, and clinical signs.
- Spiroplasma recovery and quantification were performed in brain and spleen tissues at various time points.
Main Results:
- No mortality was observed, but rats exhibited localized alopecia and significant body weight reduction.
- Ocular pathologies including cataracts, retinal degeneration, and panophthalmitis were noted.
- Spiroplasmas were recovered from the brain and spleen, with initial high titers in the spleen that declined over time, while brain titers increased, eventually exceeding spleen titers by day 50.
Conclusions:
- Peripheral inoculation of Spiroplasma mirum in rats leads to systemic infection with notable ocular and neurological manifestations.
- The observed increase in brain spiroplasma titers over the study period suggests a potential tropism for central nervous system tissues.
- Sterol nutritional dependence may influence Spiroplasma mirum's attraction to the central nervous system.