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Detection of cryptosporidia by means of molecular methods in clinical samples:infection or the transit of oocyst through the host gastrointestinal tract?
MUNZAROVÁ, Lucie
Representatives of the Cryptosporidium family are, from a medical and veterinary aspect, designated as important unicellular parasitic protozoa infecting all classes of vertebrates including humans. Their development cycle is monoxene, which means that its life cycle is completed uniquely in one host. Their exogenous stages of infection development ? oocysts ? are mostly secreted in faeces causing a parasitic disease called Cryptosporidiosis. Generally, it is assumed that isolated cryptosporidia from one class of vertebrates are not contagious for other hosts from different classes, and also, that the majority of cryptosporidia types and genotypes have low host specifity. However, there are many cases where the presence of oocysts was proved, or the presence of specific cryptosporidium DNA in faeces of atypical hosts. With regard to the fact that the majority of genotypes and their potential hosts were described only on the basis of the presence of the specific cryptosporidium DNA in faeces, the question arises as to whether the aforementioned hosts are in all cases perceptive to the given infection, or it was only contamination in a sample or the transit of oocysts through the host gastrointestinal tract. This issue is also characterised as being the main objective of this thesis. The study gives an appropriate answer to this question by a series of experiments. Different isolations of cryptosporidia were used for experimental infection of rodents which were per orally infected and put down after reaching the specified patent period. By means of the combination of standard parasitological and molecular methods, the presence of oocysts and specific DNA of cryptosporidia in faeces and in mucous membrane of the gastrointestinal tract of infected hosts was observed. The results of this study prove that the transit of oocysts through the gastrointestinal tract can be detected in the interval between 6 and 24 hours after infection, yet not in every case. On the basis of this finding, the first hypothesis which stated that it is not possible to qualify explicitly by detection of a specific cryptosporidium DNA in faeces whether the infection has begun in the host or it is the transit of oocysts through the host gastrointestinal tract, was thus partially proved. On the other hand the second hypothesis stating that the specific cryptosporidium DNA in clinical samples of faeces can be detected only in cases of the host´s successful infection, was rejected.
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