Dados do Trabalho

Título

Taxonomy of Cryptosporidium parvum and Cryptosporidium hominis: still many steps to be taken

Introdução

Cryptosporidium spp. are gastrointestinal protozoan parasites that infect a wide range of hosts, including humans and animals. They are a major contributor to moderate-to-severe diarrheal disease in developing countries, particularly in young children and immunocompromised patients. Despite efforts in an attempt to unravel the inter- and intra-specific diversity, the taxonomy of these parasites remains confused and challenges still persist when trying to genotype clinical isolates.

Objetivo (s)

A computational species delimitation analysis was performed in an attempt to understand the inter- and intra-specific genetic diversity of C. parvum and C. hominis available in molecular databases.

Material e Métodos

The gp60 locus was used as molecular target and maximum likelihood algorithm was used to phylogeny inferences. The Evolutionary Significant Units (ESUs) were defined using Poisson Tree Processes (PTP) and multi-rate PTP (mPTP) approaches.

Resultados e Conclusão

Our dataset contains 3,346 sequences (~325bp), in which 3,183 were identified to the species level (C. parvum or C. hominis) and 163 were identified to the genus level (Cryptosporidium sp. or Cryptosporidium “environmental”). Both algorithms present a higher number of ESUs when compared to classical taxonomy, suggesting the existence of cryptic species in C. parvum and C. hominis. The PTP approach identified 2,185 ESUs, has proved to be more splitter profile with 2,110 ESUs inferred and no match profiles. The mPTP approach demonstrated only 16 different ESUs, with both splitter and lumper with six ESUs each. No match profiles were identified by mPTP approach as well. The lack of matches indicates that the current taxonomy is not covering the high genetic divergence of Cryptosporidium species, which may explain the high amount of different ESUs found. Furthermore, our results demonstrated 139 and 71 taxonomically unidentified sequences by mPTP and PTP, respectively. We highlight the need to revise the taxonomic classification of the species C. parvum and C. hominis.

Palavras-chave

computational species delimitation; single-locus; molecular phylogeny

Agradecimentos

This work was supported by Faculdade de Farmácia UFJF and Programa de Pós-graduação em Ciências Farmacêuticas UFJF.