Cryptosporidium can cause diarrhea and diagnosis classically relies on the presence of acid-fast cysts in the stool.
Cryptosporidium can cause diarrhea in both the immunocompromised and the immunocompetent. In immunocompromised patients, it can cause a severe diarrhea which may result in losses of 3-17 L of stool per day. In immunocompetent individuals, it causes a milder diarrhea. Transmission is fecal-oral. In immunocompetent individuals, the disease is self-limiting, but in immunocompromised individuals it is difficult to treat. For treatment, physicians may try nitazoxanide, paromomycin,or azithromycin.
Juckett et al. discuss the diagnosis of Cryptosporidium diarrhea. Cryptosporidium (as well as Giardia) are easily missed on routine ova and parasite stool exams. Stool acid-fast staining readily identifies Cryptosporidium in the hands of a skilled microscopist.
Agnamey et al. further review diagnosis of Cryptosporidium diarrhea. The authors performed an RCT comparing different antigen tests for Cryptosporidium. The authors report that despite good specificity for the antigen tests, sensitivity was low, particularly for species of Cryptosporidium other than C. parvum or C. hominis. However, the authors conclude that the antigen test is still useful in settings where no skilled microscopist is available.
Figure A shows an acid-fast stool stain of Cryptosporidium, which was instrumental to the diagnosis here. Illustration A shows the microscopic appearance of Giardia. While Giardia may cause a similar presentation, the microscopic exam in this case is diagnostic of Cryptosporidium.
Answer 1: While Giardia can cause a similar presentation, the microscopic exam showing acid-fast oocysts is characteristic of Cryptosporidium.
Answer 3: E. coli is a very common cause of traveler's diarrhea; however, the microscopic exam showing acid-fast oocysts is characteristic of Cryptosporidium.
Answers 4-5: S. aureus and B. cereus can cause food poisoning, which may present with diarrhea, usually along with vomiting. Moreover, the microscopic exam showing acid-fast oocysts is characteristic of Cryptosporidium.
Juckett G1, Trivedi R. Evaluation of chronic diarrhea. Am Fam Physician. 2011 Nov 15;84(10):1119-26.
PMID:22085666 (Link to Abstract)
Agnamey P, Sarfati C, Pinel C, Rabodoniriina M, Kapel N, Dutoit E, Garnaud C, Diouf M, Garin JF, Totet A, Derouin F; ANOFEL Cryptosporidium National Network. Evaluation of four commercial rapid immunochromatographic assays for detection of Cryptosporidium antigens in stool samples: a blind multicenter trial. J Clin Microbiol. 2011 Apr;49(4):1605-7. doi: 10.1128/JCM.02074-10. Epub 2011 Feb 2.
PMID:21289154 (Link to Abstract)