<prompt> The common causative agent in diarrhea in AIDS patients is:ToxoplasmaCryptosporidiumSalmonellaeMycobacteria  <response>: Cryptosporidium 589-A 7th Cryptosporidium has assumed great importance as a frequent cause of intractable diarrhoea in AIDS patients. It can lead to acute self limited diarrhoea in previously healthy persons and chronic life threatening diarrhoea in immunocompromised. 