Abstract
BackgroundChagas disease is caused by Trypanosoma cruzi, which is transmitted by triatomine vectors. The northeastern region of Brazil is endemic for Chagas disease and has the largest diversity of triatomine species. T. cruzi development in its triatomine vector depends on diverse factors, including the composition of bacterial gut microbiota.MethodsWe characterized the triatomines captured in the municipality of Russas (Ceará) by sequencing the cytochrome c oxidase subunit I (COI) gene. The composition of the bacterial community in the gut of peridomestic Triatoma brasiliensis and Triatoma pseudomaculata was investigated using culture independent methods based on the amplification of the 16S rRNA gene by polymerase chain reaction (PCR), denaturing gradient gel electrophoresis (DGGE), DNA fragment cloning, Sanger sequencing and 454 pyrosequencing. Additionally, we identified TcI and TcII types of T. cruzi by sequencing amplicons from the gut metagenomic DNA with primers for the mini-exon gene.ResultsTriatomines collected in the peridomestic ecotopes were diagnosed as T. pseudomaculata and T. brasiliensis by comparing their COI sequence with GenBank. The rate of infection by T. cruzi in adult triatomines reached 80% for T. pseudomaculata and 90% for T. brasiliensis. According to the DNA sequences from the DGGE bands, the triatomine gut microbiota was primarily composed of Proteobacteria and Actinobacteria. However, Firmicutes and Bacteroidetes were also detected, although in much lower proportions. Serratia was the main genus, as it was encountered in all samples analyzed by DGGE and 454 pyrosequencing. Members of Corynebacterinae, a suborder of the Actinomycetales, formed the next most important group. The cloning and sequencing of full-length 16S rRNA genes confirmed the presence of Serratia marcescens, Dietzia sp., Gordonia terrae, Corynebacterium stationis and Corynebacterium glutamicum.ConclusionsThe study of the bacterial microbiota in the triatomine gut has gained increased attention because of the possible role it may play in the epidemiology of Chagas disease by competing with T. cruzi. Culture independent methods have shown that the bacterial composition of the microbiota in the guts of peridomestic triatomines is made up by only few bacterial species.Electronic supplementary materialThe online version of this article (doi:10.1186/s13071-015-0836-z) contains supplementary material, which is available to authorized users.
Highlights
Chagas disease is caused by Trypanosoma cruzi, which is transmitted by triatomine vectors
Triatoma species with similar morphological features are endemic in Russas, which motivated the molecular approach based on c oxidase subunit I (COI) sequencing for unequivocal species identification
Overall, we demonstrate that the different culture independent analyses used here yielded similar albeit not identical results concerning the microbiota of T. brasiliensis and T. pseudomaculata
Summary
Chagas disease is caused by Trypanosoma cruzi, which is transmitted by triatomine vectors. Triatoma brasiliensis and Triatoma pseudomaculata are two species of triatomines mainly found in the northeastern region of Brazil, which is considered the epicenter of their dispersion [2,3] and is ranked as the largest region in triatomine diversity [4] These two vector species show eclectic behavior in relation to the ecotopes where they are found (sylvatic, domestic and peridomestic), raising the question of their respective epidemiological importance in the transmission of T. cruzi to humans [5]. The coexistence of dogs in these rural areas serves as alternative reservoir with close contact to humans, making peridomestic habitats an interface with specific features compared to the habitats in the wild and domestic areas Because of these specificities, triatomine vectors in peridomestic habitats may house microbiota different from the wild habitat, which may have epidemiological consequences for Chagas disease [8]
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