In an immunocompromised patient, which pathogen is most likely to cause diarrhea?

In an immunocompromised patient, Cryptosporidium is particularly notable as a pathogen that can lead to diarrhea. This protozoan parasite is known to cause gastrointestinal illness, especially in individuals with weakened immune systems, such as those living with HIV/AIDS or undergoing chemotherapy. In these patients, the ability to fight off infections is compromised, allowing opportunistic pathogens like Cryptosporidium to thrive and cause significant illness. The diarrhea associated with Cryptosporidium can be prolonged and severe, contributing to dehydration and further complications.

While the other pathogens listed can cause gastrointestinal symptoms, they are not as directly associated with diarrhea in immunocompromised patients. For instance, E. coli strains may cause diarrhea, but they are more commonly associated with immunocompetent individuals or specific outbreaks. Helminths can lead to gastrointestinal symptoms as well, but they generally cause more chronic or subtle symptoms rather than acute diarrhea. Clostridium difficile is another important pathogen, especially in patients who have received antibiotics; however, it is less specifically associated with immunocompromised states compared to Cryptosporidium.