The interactions between intestinal microbiota, immune system, and pathogens describe the human gut as a complex ecosystem, where all components play a relevant role in modulating each other and in the maintenance of homeostasis. The balance among the gut microbiota and the human body appear to be crucial for health maintenance. Intestinal parasites, both protozoans and helminths, interact with the microbial community modifying the balance between host and commensal microbiota. On the other hand, gut microbiota represents a relevant factor that may strongly interfere with the pathophysiology of the infections. In addition to the function that gut commensal microbiota may have in the processes that determine the survival and the outcome of many parasitic infections, including the production of nutritive macromolecules, also probiotics can play an important role in reducing the pathogenicity of many parasites. On these bases, there is a growing interest in explaining the rationale on the possible interactions between the microbiota, immune response, inflammatory processes, and intestinal parasites.

Blastocystis sp. is the most common eukaryotic parasite in the intestinal tract of humans. Due to its potential impact in public health, we determined the Blastocystis sp. subtypes (STs) and their relative frequency in symptomatic patients living in or in the vicinity of two Italian cities (Rome and Sassari). A total of 34 Blastocystis sp. isolates corresponding to 26 single and 4 mixed infections were subtyped using partial small subunit ribosomal RNA gene sequencing. From this molecular approach, the ST distribution in the present Italian population was as follows: ST3 (47.1%), ST2 (20.6%), ST4 (17.7%), ST1 (8.8%), and ST7, and ST8 (2.9%). As in almost all countries worldwide, ST3 was the most common ST reinforcing the hypothesis of its human origin. Together with a previous preliminary report, a total of seven STs (with the addition of ST5) have been found in Italian symptomatic patients. The wide range of STs identified in the Italian population suggest that Blastocystis sp. infection is not associated with specific STs even if some STs (ST1-ST4) are predominant as reported in all other countries. Since most of the STs identified in Italian patients are zoonotic, our data raise crucial questions concerning the identification of animal reservoirs for Blastocystis sp. and the potential risks of transmission to humans.

Introduction: Literature data provide little information about protozoa infections and gut microbiota compositional shifts in humans. This preliminary study aimed to describe the fecal bacterial community composition of people from Côte d'Ivoire harboring Giardia duodenalis, Entamoeba spp., and Blastocystis hominis, in trying to discover possible alterations in their fecal microbiota structure related to the presence of such parasites. Methodology: Twenty fecal samples were collected from people inhabiting three different localities of Côte d'Ivoire for copromicroscopic analysis and molecular identification of G. duodenalis, Entamoeba spp., and B. hominis. Temporal temperature gradient gel electrophoresis (TTGE) was used to obtain a fingerprint of the overall bacterial community; quantitative polymerase chain reaction (qPCR) was used to define the relative abundances of selected bacterial species/group, and multivariate statistical analyses were employed to correlate all data. Results: Cluster analysis revealed a significant separation of TTGE profiles into four clusters (p < 0.0001), with a marked difference for G. duodenalis-positive samples in relation to the others (p = 5.4×10 -6 ). Interestingly, qPCR data showed how G. duodenalis-positive samples were related to a dysbiotic condition that favors potentially harmful species (such as Escherichia coli), while Entamoeba spp./B. hominis-positive subjects were linked to a eubiotic condition, as shown by a significantly higher Faecalibacterium prausnitzii-Escherichia coli ratio. Conclusions: This preliminary investigation demonstrates a differential fecal microbiota structure in subjects infected with G. duodenalis or Entamoeba spp./B. hominis, paving the way for using further next-generation DNA technologies to better understand host-parasite-bacteria interactions, aimed at identifying potential indicators of microbiota changes.

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In order to investigate the genotypes of Giardia duodenalis from domestic and farm animals in Italy, 21 Giardia isolates, 17 from dogs, 1 from cat and 3 from dairy calves, were genetically characterised by SSU-rRNA gene sequencing. Among dogs, 76.5% of isolates showed the dog-specific genotypes (Assemblages C, D and C/D mixed Assemblage) and 23.5% exhibit potential zoonotic genotypes (Assemblage A and A/C mixed Assemblages). The cat isolate belonged to assemblage A, whereas the sequences among the isolates from calves were found to correspond to hoofed-livestock genotype, namely Assemblage E. These findings suggest that infection of humans by zoonotic genotypes from domestic animals could be of low epidemiological significance, although possible. The present study represents the first contribute to the knowledge of G. duodenalis genotypes in domestic and farm animals from Italy.