Objective: Cryptosporidium parvum is associated with persistent diarrhoea and malnutrition in children, with large waterborne outbreaks and with the diarrhoea-wasting syndrome in AIDS. However, pathophysiology of infection remains to be defined and the reasons for the variability of clinical features are uncertain. The polymerase chain reaction (PCR) is valuable for the analysis of infections with non-culturable organisms because of its high sensitivity, so we compared PCR and microscopy as tools for the analysis of the distribution of infection.
Design: PCR was compared with light microscopy (LM) and electron microscopy (EM) in duodenal biopsies from a well characterized series of 75 Zambian AIDS patients. PCR and LM were then used to define the distribution of infection in biopsies from duodenum, ileum, right colon and left colon in eight South African patients with persistent AIDS-related cryptosporidiosis.
Results: PCR specifically detected 10 fg of genomic C. parvum DNA. When applied to duodenal biopsies from 75 Zambian AIDS patients, infection was detected in all seven cases of duodenal cryptosporidiosis that were identified by LM or EM and in six additional cases which appeared to be negative by microscopy. Distribution of infection was defined in six of eight South African AIDS patients. Two had pan-enteric infection, three had small bowel infection and one had purely ileo-colonic infection. In two cases infection could not be localized despite using PCR, suggesting that infection was confined to the inaccessible mid-small intestine.
Conclusions: PCR detection of C. parvum DNA demonstrated that infection is highly variable in distribution, which must be taken into account when designing and interpreting studies of pathophysiology.