MixedCryptosporidiumInfections and HIV

Mixed Cryptosporidium infections were detected in 7 of 21 patients with a diagnosis of rare Cryptosporidium canis or C. felis infections; 6 patients were infected with 2 Cryptosporidium spp.and 1 patient with 3 species.Mixed infections may occur more frequently than previously believed and should be considered when assessing cryptosporidiosis.C ryptosporidium spp.infect humans and other verte- brate animals.Persons with compromised immune systems can suffer life-threatening chronic diarrhea, especially when their CD4+ lymphocyte counts fall <200 cells/µL.At least 7 Cryptosporidium spp.have been detected in immunocompromised patients (1).Nonetheless, the role of concurrent or mixed infections in the pathogenesis and transmission of Cryptosporidium spp. is unclear.Mixed infections of Cryptosporidium hominis and C. parvum have been reported in several patients from Switzerland and England (2,3).Additional studies from the United Kingdom reported simultaneous infections with these 2 species: 4 cases in 2 waterborne outbreaks and 2 cases of sporadic infections from 1995 to 1999 (4).In a more recent study, 12% of 135 clinical specimens from Aberdeenshire, Scotland, had concurrent C. parvum and C. hominis infections (5).Mixed C. hominis-C.parvum infections were also seen in 2 of 38 archived human specimens in a study conducted in the United States (6).These observations suggest that mixed Cryptosporidium infections are not uncommon.Mixed infections may not be readily identified by commonly used molecular diagnostic tools because of preferential polymerase chain reaction (PCR) amplification of the predominant genotypes or the specificity of molecular tools (6).For example, PCR-restriction fragment length polymorphism (RFLP) tools based on the small subunit (SSU) rRNA gene are frequently used in genotyping Cryptosporidium spp.because they have higher sensitivity