Immunohistochemical observations on pneumonic lesions caused by Rhodococcus equi in foals.

The study investigates how Rhodococcus equi bacteria affects pneumonia in foals using immunohistochemical analysis. The findings suggest that this bacteria has protective attributes that defend it against the immune response.

Methodology

• An immunohistochemical test was carried out on ten foals suffering from pneumonia caused by Rhodococcus equi.
• The research utilized the biotin-streptavidin system to assess how effectively R. equi was detected. This was compared to the effectiveness of Gram’s stain, a method commonly used to distinguish bacterial species.
• The team also explored how well this bacterium responded to anti-BCG serum, a tuberculosis vaccine.

Observations

• In the affected foals, R. equi was detectable in macrophages, a type of white blood cell, along with lysozyme and alpha 1-antitrypsin.
• An intense staining was observed in response to these intracellular (within the cell) bacteria, suggesting a strong reaction.
• The team also recognized a low reaction for alpha 1-antichymotrypsin when compared to lysozyme and alpha 1-antitrypsin. Nonetheless, it was also visible in the macrophages.

Conclusion

• The researchers found that the bacteria appeared almost unharmed when examined under an electron microscope. This led them to surmise that certain surface components of the R.equi bacteria may defend it against the intracellular degradation efforts of the macrophages.
• The team observed that the cells containing intracytoplasmic immunoglobulins IgM, IgG, or IgA were few and dispersed mainly around the pneumonia site. This led them to speculate that the ability of these immunoglobulins to kill bacteria may be weaker than the phagocytosis ability of macrophages.