Specific and quantitative detection and identification of Cryptosporidium hominis and C. parvum in clinical and environmental samples.

Cryptosporidium is an enteric protozoan parasite that is resistant to inactivation by commonly used drinking water disinfectants. Between 2004 and 2010, it was responsible for 60% of all waterborne protozoan parasitic outbreaks reported worldwide. Most sporadic infections in humans and almost all outbreaks are caused by Cryptosporidium parvum and Cryptosporidium hominis. We report the development and validation of a quantitative qPCR assay using minor groove binder (MGB)-probes targeting a unique Cryptosporidium specific protein-coding gene, that directly detects, quantitates and identifies C. hominis and C. parvum in environmental and faecal samples. An internal amplification control (IAC) was also developed and included in this assay. The qPCR assay was compared with an 18S nested PCR assay for sensitivity and specificity. The analytical sensitivity for the qPCR assay was 1 oocyst and 1-10 oocysts for the 18S assay. Evaluation of analytical specificity of the qPCR assay revealed no cross-reactions with other genera and detected all C. parvum and C. hominis isolates correctly. The diagnostic sensitivity and specificity of the qPCR was 100% compared to 96.9% and 98.4%, respectively for the 18S assay. The qPCR assay was also highly reproducible with RSD (relative standard deviation) values of 1.4-9.4%, when the assay was performed by four different technicians. When tested on water samples, the qPCR assay was more sensitive than the 18S assay, detecting positives in 37 of 138 water samples compared to 35 for the 18S locus. This qPCR assay should be a valuable tool for the detection and differentiation of C. hominis and C. parvum in both clinical and environmental samples.

Complete development and multiplication of Cryptosporidium hominis in cell-free culture.

The present study reports for the first time the completion of the life cycle of Cryptosporidium hominis in cell-free culture and multiplication of the parasite via qPCR. Individual life-cycle stages were characterised using Cryptosporidium-specific antibody staining (Sporo-Glo) and fluorescent in situ hybridisation (FISH) staining on cultures inoculated with excysted oocysts and purified sporozoites. In both cultures, C. hominis successfully proliferated and completed its life cycle, however development in cultures inoculated with purified sporozoites lagged behind cultures inoculated with excysted oocysts. Some novel findings of the study include the visualisation of pairing and multiple associations between various developmental stages in a process similar to syzygy and the formation of Cryptosporidium stages (trophozoites and meronts) inside the oocysts without excystation. qPCR analysis revealed a 5-6-fold amplification of parasite DNA. Future studies are required to improve the amplification of the parasite. The present study confirms the suitability of this culturing model to support the growth and proliferation of C. hominis (which unlike C. parvum, cannot be readily cultured in small animal models) and will greatly assist in our understanding of the developmental biology of Cryptosporidium, its position within the Apicomplexa and its relationship to gregarine protozoa.

Echinococcus granulosus cattle strain identification in an autochthonous case of cystic echinococcosis in central Mexico.

Echinococcosis is a frequent hepatic parasitic disease in several countries but it is practically absent in Mexico. A cattle strain of Echinococcus granulosus was identified by RAPD, PCR-RFLP and mitochondrial CO1 gene analysis in an autochthonous case. The parasite was obtained after a laparoscopic excision of a liver cyst from a patient that was symptomatic for 6 years but mis-diagnosed before hospitalization.