Dientamoeba fragilis: Técnicas moleculares para dilucidar su modo de transmisión <span class="so-article-trans-title" dir="auto"> Translated title: Dientamoeba fragilis: MOLECULAR BIOLOGY TECHNIQUES FOR THE ELUCIDATION OF ITS MODE OF TRANSMISSION </span>

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Abstract

Dientamoeba fragilis es un protozoario intestinal humano. Su prevalencia mundial oscila aproximadamente entre 1,4% y 19%. Muy poco se sabe actualmente sobre su virulencia, patogenicidad, modo de transmisión; y no se ha identificado aún un estadio quístico. Un amplio espectro de síntomas gastrointestinales ha sido descrito en un gran número de pacientes infectados: diarrea, flatulencia, cólicos, y pérdida de peso, entre otros. La asociación simultánea entre las infecciones causadas por D. fragilis y Enterobius vermicularis llevó a Burrows y Swerdlow en 1956 a especular sobre el probable rol de los huevos de E. vermicularis en la transmisión. Este trabajo es la primera tentativa para detectar la presencia del DNA de D. fragilis en los huevos de E. vermicularis. Para ello se realizó un ensayo con DNasa y posterior verificación de la identidad mediante un análisis de restricción enzimática de los productos de PCR con HinfI, en infecciones simultáneas con ambos parásitos. A nivel mundial, la enterobiosis es muy frecuente. En los pacientes pediátricos con evidencia directa de infección por E. vermicularis, deberá intensificarse la búsqueda de D. fragilis en materia fecal

Translated abstract

Dientamoeba fragilis is a human intestinal protozoon. Its worldwide prevalence ranges mostly between 1.4% and 19%. Very little is known to date about its virulence, pathogenicity, and mode of transmission; and no cyst stage has been identified yet. A wide spectrum of gastrointestinal symptoms has been described in a great number of infected patients: diarrhoea, flatulence, colic, and weight loss, amongst others. The simultaneous association between infections with D. fragilis and those caused by Enterobius vermicularis lead Burrows and Swerdlow in 1956 to speculate about the probable role of pinworm eggs in transmission. This work is the first attempt to detect the presence of D. fragilis DNA on the outer shell of E. vermicularis eggs, by means of a DNase assay and posterior identity verification by means of a restriction digest analysis of PCR products with HinfI, in co-infections with both parasites. Enterobiosis is extremely prevalent in human beings worldwide. In paediatric patients with direct evidence of pinworm infection, the search for D. fragilis should be enhanced

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Emerging from obscurity: biological, clinical, and diagnostic aspects of Dientamoeba fragilis.

Mark H. Johnson, Jimmy Windsor, Kaitlin C Clark (2004)

Ever since its first description in 1918, Dientamoeba fragilis has struggled to gain recognition as a significant pathogen. There is little justification for this neglect, however, since there exists a growing body of case reports from numerous countries around the world that have linked this protozoal parasite to clinical manifestations such as diarrhea, abdominal pain, flatulence, and anorexia. A number of studies have even incriminated D. fragilis as a cause of irritable bowel syndrome, allergic colitis, and diarrhea in human immunodeficiency virus patients. Although D. fragilis is most commonly identified using permanently stained fecal smears, recent advances in culturing techniques are simplifying as well as improving the ability of investigators to detect this organism. However, there are limitations in the use of cultures since they cannot be performed on fecal samples that have been fixed. Significant progress has been made in the biological classification of this organism, which originally was described as an ameba. Analyses of small-subunit rRNA gene sequences have clearly demonstrated its close relationship to Histomonas, and it is now known to be a trichomonad. How the organism is transmitted remains a mystery, although there is some evidence that D. fragilis might be transmitted via the ova of the pinworm, Enterobius vermicularis. Also, it remains to be answered whether the two distinct genotypes of D. fragilis recently identified represent organisms with differing virulence.

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Development and laboratory evaluation of a polymerase chain reaction for monitoring Schistosoma mansoni infestation of water.

Reda M. R. Ramzy, J Hamburger, A Ruppel … (1998)

A sensitive and specific detection of cercariae of human schistosomes is required for better definition of risk of infection. In the present study, we have developed a polymerase chain reaction (PCR) assay for the detection of cercariae of Schistosoma mansoni in water. A simple DNA preparation was adapted for this purpose, and PCR primers were designed based on the 121-basepair highly repeated sequence we previously identified in the genome of S. mansoni. The PCR assay detected as little as 10(-6) ng of S. mansoni DNA, and the high sensitivity enabled the detection of a single cercaria. For trapping of cercariae we adapted a filtration apparatus previously used for separating schistosome eggs from turbid enzymatic digests of tissues. A single cercaria could be detected in repeated tests of water filtrates. Since the target DNA is tandemly arranged, a ladder pattern of the PCR products was demonstrated. A direct relationship was demonstrated between the number of ladder bands of the amplification products, and DNA concentration or number of cercariae. The feasibility of semiquantitation of schistosome larvae in natural water was thus suggested. The potential of the procedures described here for epidemiologic studies is discussed.