Amoebae are single-celled parasites frequently colonizing human gut. However, few molecular tools are available for accurate identification. Here, we evaluated a panel of polymerase chain reactions (PCRs) targeting Entamoeba histolytica, Entamoeba dispar, Entamoeba coli, Entamoeba hartmanni, Entamoeba polecki, Endolimax nana and Iodamoeba bütschlii. Thirty-six faecal samples (18 containing at least one amoeba species by microscopy and 18 microscopy negative for amoebae) were tested. Real-time PCRs were used for detection and differentiation of E. histolytica and E. dispar. Conventional PCR with Sanger sequencing were applied for detection and differentiation of E. coli, E. hartmanni, E. polecki, E. nana and I. bütschlii. All microscopy results were confirmed by DNA-based methods. However, more samples were positive for single and mixed amoebic species by DNA-based assays than by microscopy (22 vs 18 and 7 vs 1, respectively). DNA sequencing allowed identification of E. coli subtypes (ST1 and ST2), showed low intra-specific variation within E. hartmanni, identified two phylogenetically distinct groups within E. nana, and identified Iodamoeba at the ribosomal lineage level. Taking into account the high intra-genetic diversity within some of the species at the small subunit (SSU) rRNA gene level, amplification of SSU rRNA genes with subsequent sequencing represents a useful method for detecting, differentiating and subtyping intestinal amoebae.

The human oro-gastrointestinal (GI) tract is a complex system, consisting of oral cavity, pharynx, oesophagus, stomach, small intestine, large intestine, rectum and anus, which all together with the accessory digestive organs constitute the digestive system. The function of the digestive system is to break down dietary constituents into small molecules and then absorb these for subsequent distribution throughout the body. Besides digestion and carbohydrate metabolism, the indigenous microbiota has an important influence on host physiological, nutritional and immunological processes, and commensal bacteria are able to modulate the expression of host genes that regulate diverse and fundamental physiological functions. The main external factors that can affect the composition of the microbial community in generally healthy adults include major dietary changes and antibiotic therapy. Changes in some selected bacterial groups have been observed due to controlled changes to the normal diet e.g. high-protein diet, high-fat diet, prebiotics, probiotics and polyphenols. More specifically, changes in the type and quantity of non-digestible carbohydrates in the human diet influence both the metabolic products formed in the lower regions of the GI tract and the bacterial populations detected in faeces. The interactions between dietary factors, gut microbiota and host metabolism are increasingly demonstrated to be important for maintaining homeostasis and health. Therefore the aim of this review is to summarise the effect of diet, and especially dietary interventions, on the human gut microbiota. Furthermore, the most important confounding factors (methodologies used and intrinsic human factors) in relation to gut microbiota analyses are elucidated.