The organism most frequently related to mediastina fibrosis is
Fibrosing mediastinitis or mediastinal fibrosis is the least common,but the most severe ,late complication of histoplasmosis.It is due to an abnormal immunological response to antigens released by the soil based fungus Histoplasma capsulatum.It is characterised by invasive calcified fibrosis centered at locations of lymph nodes,which occludes major vessels & airways.
Actinomycosis
Histoplasma
Hansen's bacillus
Staphylococcus
Cardio thoracic surgery  