Cryptosporidiosis in persons with HIV infection

Specific and genotypic identification of Cryptosporidium from a broad range of host species by nonisotopic SSCP analysis of nuclear ribosomal DNA

The accurate identification of Cryptosporidium (Protozoa: Apicomplexa) species and genotypes is central to the understanding of the transmission and to the diagnosis and control of cryptosporidiosis. In this study, we demonstrate the effectiveness of nonisotopic SSCP analysis of a approximately 300 bp region of the small subunit (pSSU) of ribosomal DNA for the specific identification of and delineation among 18 different Cryptosporidium species and genotypes from a wide range of hosts. This mutation scanning approach allowed the rapid and reliable differentiation between species/genotypes differing by as little as 1.3% in the pSSU sequence, with the capacity to detect point mutations. The present findings confirm the usefulness of this tool for the rapid genetic screening of Cryptosporidium samples from any host species, providing a foundation for detailed systematic, epidemiological and ecological studies. Although applied herein to pSSU, this low cost approach should be applicable to a wide range of genetic loci for population genetic investigations of Cryptosporidium.

Batch solar disinfection inactivates oocysts of Cryptosporidium parvum and cysts of Giardia muris in drinking water

AIM

To determine whether batch solar disinfection (SODIS) can be used to inactivate oocysts of Cryptosporidium parvum and cysts of Giardia muris in experimentally contaminated water.

METHODS AND RESULTS

Suspensions of oocysts and cysts were exposed to simulated global solar irradiation of 830 W m(-2) for different exposure times at a constant temperature of 40 degrees C. Infectivity tests were carried out using CD-1 suckling mice in the Cryptosporidium experiments and newly weaned CD-1 mice in the Giardia experiments. Exposure times of > or =10 h (total optical dose c. 30 kJ) rendered C. parvum oocysts noninfective. Giardia muris cysts were rendered completely noninfective within 4 h (total optical dose >12 kJ). Scanning electron microscopy and viability (4',6-diamidino-2-phenylindole/propidium iodide fluorogenic dyes and excystation) studies on oocysts of C. parvum suggest that inactivation is caused by damage to the oocyst wall.

CONCLUSIONS

Results show that cysts of G. muris and oocysts of C. parvum are rendered completely noninfective after batch SODIS exposures of 4 and 10 h (respectively) and is also likely to be effective against waterborne cysts of Giardia lamblia.

SIGNIFICANCE AND IMPACT OF THE STUDY

These results demonstrate that SODIS is an appropriate household water treatment technology for use as an emergency intervention in aftermath of natural or man-made disasters against not only bacterial but also protozoan pathogens.

Enzymatic hydrolysis of diloxanide furoate in the presence of β-cyclodextrin and its methylated derivatives

In this study, we investigated the susceptibility to enzymatic and alkaline hydrolysis of diloxanide furoate (DF) and its cyclodextrin inclusion complexes, in aqueous solution. The cyclodextrins (CDs) utilized were beta-cyclodextrin (beta-CD), (2,6-di-O-methyl)-beta-cyclodextrin (DM-beta-CD) and (2,3,6-tri-O-methyl)-beta-cyclodextrin (TM-beta-CD). All cyclodextrins studied provided a stabilizing effect to diloxanide furoate hydrolysis. In alkaline hydrolysis (pH 10.75), without the enzyme, beta-CD and TM-beta-CD provided similar effect on the stability of DF, with an inhibition factor in the order of 2.0. The DM-beta-CD, on the other hand, provided more pronounced stabilization effect than the other two CDs, with an inhibition factor around of 8. The maximum activity of the enzyme occured around pH 7.0. In the presence of enzyme, all cyclodextrins produced similar effect, with a DF hydrolysis inhibition factor in the order of 10. However, the plot of rate of hydrolysis versus [CD] fit with a equation based in a model that considers the association of the enzyme with the CDs. Therefore, it is concluded that the stabilization of DF is not only due to its cyclodextrin complex but also due to enzyme inhibition by cyclodextrin complexation.

New insights into human cryptosporidiosis

Cryptosporidium parvum is an important cause of diarrhea worldwide. Cryptosporidium causes a potentially life-threatening disease in people with AIDS and contributes significantly to morbidity among children in developing countries. In immunocompetent adults, Cryptosporidium is often associated with waterborne outbreaks of acute diarrheal illness. Recent studies with human volunteers have indicated that Cryptosporidium is highly infectious. Diagnosis of infection with this parasite has relied on identification of acid-fast oocysts in stool; however, new immunoassays or PCR-based assays may increase the sensitivity of detection. Although the mechanism by which Cryptosporidium causes diarrhea is still poorly understood, the parasite and the immune response to it probably combine to impair absorption and enhance secretion within the intestinal tract. Important genetic studies suggest that humans can be infected by at least two genetically distinct types of Cryptosporidium, which may vary in virulence. This may, in part, explain the clinical variability seen in patients with cryptosporidiosis.