104 Inhibition of bacterial cysteine proteases have been tested by cystatins C, SN, S and chicken cystatin and they are generaly inactive against bacterial cysteine proteases. [105] [106] [107] In contrast to bacterial cysteine proteases, they are more efficient against cysteine proteases from parasits; for example, cystatins SA and SN are inhibitors of trypanosome cruzain 108 , chicken cystatin inhibits congopain from Trypanosoma congolense 109 and cruzipain, the major cysteine proteinase of the protozoan parasite Trypanosoma cruzi.