DNA of Dientamoeba fragilis detected within surface-sterilized eggs of Enterobius vermicularis

With no evidence of a cyst stage, the mode of transmission of Dientamoeba fragilis, an intestinal protozoon of common occurrence and suggested pathogenicity, is incompletely known. Numerous studies have suggested that eggs of intestinal nematodes, primarily Enterobius vermicularis (pinworm), can serve as vectors for D. fragilis, although attempts to culture D. fragilis from pinworm eggs have been unsuccessful and data from epidemiological studies on D. fragilis/pinworm co-infection have been conflicting.The aim of this study was to investigate whether we could detect D. fragilis DNA from pinworm eggs collected from routine diagnostic samples (cellophane tape) and surface-sterilised by hypochlorite. DNA was extracted from individual eggs and tested by PCR using D. fragilis- and E. vermicularis-specific primers; amplicons were sequenced for confirmation.In cellophane tape samples from 64 patients with unknown D. fragilis status we detected D. fragilis DNA in 12/238 (5%) eggs, and in a patient known to harbour D. fragilis we detected D. fragilis DNA in 39/99 (39%) eggs.The finding of D. fragilis DNA within eggs of E. vermicularis strongly supports the hypothesis of D. fragilis-transmission by pinworm and has implications for antimicrobial intervention as well as control and public health measures.

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► Eggs of Enterobius vermicularis were surface-sterilized using hypochlorite.
► DNA was extracted from individual eggs.
► Dientamoeba fragilis and E. vermicularis PCR was performed on DNA extracts.
► Sequencing of PCR amplicons showed evidence of D. fragilis-specific DNA.
► Results support hypothesis of D. fragilis transmission by E. vermicularis.