RESUMO
Babesia spp. are obligate protozoan parasites of red blood cells. Transmission to humans occurs through bites from infected ticks or blood transfusion. Infections with B. microti account for the majority of the reported cases of human babesiosis in the USA. A lower incidence is caused by the more recently described species B. duncani. The current gold standard for detection of Babesia is microscopic examination of blood smears. Recent PCR-based assays, including real-time PCR, have been developed for B. microti. On the other hand, molecular assays that detect and distinguish between B. microti and B. duncani infections are lacking. Closely related species of Babesia can be differentiated due to sequence variation within the internal transcribed spacer (ITS) regions of nuclear ribosomal RNAs. In the present study, we targeted the ITS regions of B. microti and B. duncani to develop sensitive and species-specific droplet digital PCR (ddPCR) assays. The assays were shown to discriminate B. microti from B. duncani and resulted in limits of detection of ~10 gene copies. Moreover, ddPCR for these species were useful in DNA extracted from blood of experimentally infected hamsters, detecting infections of low parasitemia that were negative by microscopic examination. In summary, we have developed sensitive and specific quantitative ddPCR assays for the detection of B. microti and B. duncani in blood. Our methods could be used as sensitive approaches to monitor the progression of parasitemia in rodent models of infection as well as serve as suitable molecular tests in blood screening.
Assuntos
Babesia/isolamento & purificação , Reação em Cadeia da Polimerase/métodos , Animais , Babesia/classificação , Babesia/genética , Babesia microti/classificação , Babesia microti/genética , Babesia microti/isolamento & purificação , Sequência de Bases , Cricetinae , DNA Intergênico/química , DNA de Protozoário/sangue , DNA Ribossômico/química , Mesocricetus , Dados de Sequência Molecular , RNA Ribossômico 18S/genética , RNA Ribossômico 28S/genética , RNA Ribossômico 5,8S/genética , Reação em Cadeia da Polimerase em Tempo Real , Sensibilidade e EspecificidadeRESUMO
We describe the isolation of a mycobacterium from Acanthamoeba castellanii strain Ma (ATCC(®) 50370(™)). The mycobacterium resides within vacuoles of A. castellanii, can be cultured by routine methodologies, and is a member of the Mycobacterium avium complex. Previously unrecognized mycobacterial endosymbionts are likely common among strains of Acanthamoeba housed at culture collections.