Molecular assays to diagnose Entamoeba histolytica and Entamoeba dispar infections in a non-endemic area (Parma, Italy).

Objectives: The detection of Entamoeba histolytica (Eh), causative agent of amoebiasis, is an important goal of the clinical parasitology laboratory. The identification of E. dispar (Ed) as a morphologically identical but non-pathogenic species has highlighted the need for non-microscopic detection methods able to differentiate the 2 species. Moreover, a reassessment of the worldwide prevalence of amoebic infection based on discriminatory methods has been strongly recommended by WHO. The area in which our laboratory is located has seen in recent years an increase of people travelling through and a significant flow of immigration from tropical countries which has led to a parallel increase in imported infections. Thus, the aim of this study was to promptly diagnose and discriminate Eh and Ed infections and to assess their occurrence among patients with suspected intestinal parasitosis presenting to the University Hospital of Parma. Methods: The specimens analysed in this study were selected from the whole of the clinical samples sent to our laboratory with the suspicion of intestinal parasitosis during 2003–2007 and subjected to standard procedures (microscopic examination) for the detection of intestinal parasites. In particular, 730 samples (715 faeces, 7 liver abscess samples, 8 intestinal biopsies) belonging to 407 patients were analysed. The samples were subjected to culture for intestinal protozoa and molecular assays (conventional or Real-Time PCR) able to distinguish Eh from Ed DNA. Results: Eight patients (1.96%) proved to be infected by Eh (3 with extraintestinal and 5 with intestinal amoebiasis; 5 with imported amoebiasis and 3 with the disease acquired in Italy) and 36 by Ed (8.84%). In particular, in 4 of the 8 patients with Eh infection, only molecular methods were able to detect the presence of the parasite. Conclusion: Our results underline that traditional methods underestimate the prevalence of amoebic infection and highlight the important diagnostic role that PCR can play. Species differentiation by PCR becomes an important tool for clinicians as it permits them to focus on Eh infections and to avoid treatment when non-pathogenic Ed is present. The relatively high prevalence of Ed infections observed in this study versus the more rare Eh infections, is indicative of the existence in the community of a faecal-oral route of agents with an exclusively inter-human circulation and calls for the activation of adequate control measures.