Asymptomatic Intestinal Colonization by Pathogenic Entamoeba histolytica in Amebic Liver Abscess: Prevalence, Response to Therapy, and Pathogenic Potential

Irusen, E M; Jackson, Terry; Simjee, A. E.

doi:10.1093/clinids/14.4.889

Cited by 92 publications

(41 citation statements)

References 24 publications

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“…However, the latter is more likely, as all patients were only treated with metronidazole and none of them received a luminal antiamebic agent such as diloxanide furoate or paromomycin. A 30% E. histolytica prevalence in previous ALA patients 3 to 9 months after metronidazole therapy would be fully consistent with previous findings, which indicated a cure rate of intestinal infection by metronidazole of about 50% (12,26).…”

Section: Discussionsupporting

confidence: 90%

Real-Time PCR for Detection and Differentiation ofEntamoeba histolyticaandEntamoeba disparin Fecal Samples

et al. 2002

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A closed-tube, real-time PCR assay was developed for sensitive and specific detection and differentiation of the two closely related intestinal protozoan parasites Entamoeba histolytica and Entamoeba dispar directly from human feces. The assay is performed with the LightCycler system using fluorescence-labeled detection probes and primers amplifying a 310-bp fragment from the high-copy-number, ribosomal DNA-containing ameba episome. The assay was able to detect as little as 0.1 parasite per g of feces. The two pairs of primers used were specific for the respective ameba species, and results were not influenced by the presence of other Entamoeba species even when present in exceeding amounts. PCR was evaluated using several hundred stool samples from areas of amebiasis endemicity in Vietnam and South Africa, and results were compared with those of microscopy and ameba culture. PCR was found to be significantly more sensitive than microscopy or culture, as all samples positive by microscopy and 22 out of 25 (88%) samples positive by culture were also positive by PCR, but PCR revealed a considerable number of additional E. histolytica-or E. dispar-positive samples. Compared to culture and subsequent ameba differentiation by isoenzyme analysis, PCR was 100% specific for each of the two Entamoeba species. Interestingly, the comparison with PCR revealed that culture, in particular, underestimates E. histolytica infections. Given the high sensitivity and specificity of the developed PCR assay, the inability of microscopy to distinguish between the two ameba species, and the time it takes to culture and subsequently differentiate entamoebae by isoenzyme analysis, this assay is more suitable than microscopy or culture to correctly diagnose intestinal E. histolytica or E. dispar infection.

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Section: Discussionsupporting

confidence: 90%

Real-Time PCR for Detection and Differentiation ofEntamoeba histolyticaandEntamoeba disparin Fecal Samples

et al. 2002

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“…10 The existence of asymptomatic carriers of E. histolytica, [34][35][36][37][38] has raised doubts about the proportion of individuals infected who are truly at risk of invasive amoebiasis, and questions the human host factors, that favors this apparently commensal-like relationship with E. histolytica.…”

Section: Discussionmentioning

confidence: 99%

Differentiation of entamoeba histolytica/entamoeba dispar by PCR and their correlation with humoral and cellular immunity in individuals with clinical variants of amoebiasis.

Sánchez-Guillén¹,

Pérez-Fuentes

Salgado-Rosas

et al. 2002

The American Journal of Tropical Medicine and Hygiene

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Abstract. To correlate a particular state of immunity with Entamoeba spp., we used colorimetric PCR to differentiate E. histolytica from E. dispar in individuals with amoebiasis and to associate its presence with the clinical profile, including humoral and cellular immune responses to E. histolytica. Our results showed high levels of antibody in acute amoebiasis and elevation of IL-4 production, a cytokine related to Th2 profile, associated with E. histolytica. In chronic amoebiasis, even with anti-E. histolytica seropositivity, intestinal symptoms were associated with E. dispar in all the cases, without differences in level of antibodies, BTI, CD4+/CD8+ ratio, INF-␥, and IL-4. Among asymptomatic carriers, E. dispar was more frequently found; however, identification of E. histolytica in two asymptomatic carriers associated with high levels of INF-␥, a cytokine related to Th1 profile, demonstrate the importance of making specific diagnosis of Entamoeba spp., to establish the clinical and epidemiological behavior in both intestinal and extra-intestinal amoebiasis.

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“…This statement has support from a study of 36 patients with amoebic liver abscess for whom the hepatic lesions were cleared; but 20 were recolonized in the intestine, 16 asymptomatically. This was ascribed to the pharmacokinetics of metronidazole cycling in the liver and the action of metronidazole against trophozoites but not invariable eradication of cysts, creating E. histolytica carrier states (90,93). These figures are considerably higher than generally published, although no single treatment has claims of 100% efficacy; 90% success after 5 to 10 days of metronidazole treatment is regarded as adequate by some workers.…”

Section: Entamoeba Drug Treatment and Resistancementioning

confidence: 99%

Drug Targets and Mechanisms of Resistance in the Anaerobic Protozoa

2001

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The anaerobic protozoa Giardia duodenalis, Trichomonas vaginalis, and Entamoeba histolytica infect up to a billion people each year. G. duodenalis and E. histolytica are primarily pathogens of the intestinal tract, although E. histolytica can form abscesses and invade other organs, where it can be fatal if left untreated. T. vaginalis infection is a sexually transmitted infection causing vaginitis and acute inflammatory disease of the genital mucosa. T. vaginalis has also been reported in the urinary tract, fallopian tubes, and pelvis and can cause pneumonia, bronchitis, and oral lesions. Respiratory infections can be acquired perinatally. T. vaginalis infections have been associated with preterm delivery, low birth weight, and increased mortality as well as predisposing to human immunodeficiency virus infection, AIDS, and cervical cancer. All three organisms lack mitochondria and are susceptible to the nitroimidazole metronidazole because of similar low-redox-potential anaerobic metabolic pathways. Resistance to metronidazole and other drugs has been observed clinically and in the laboratory. Laboratory studies have identified the enzyme that activates metronidazole, pyruvate:ferredoxin oxidoreductase, to its nitroso form and distinct mechanisms of decreasing drug susceptibility that are induced in each organism. Although the nitroimidazoles have been the drug family of choice for treating the anaerobic protozoa, G. duodenalis is less susceptible to other antiparasitic drugs, such as furazolidone, albendazole, and quinacrine. Resistance has been demonstrated for each agent, and the mechanism of resistance has been investigated. Metronidazole resistance in T. vaginalis is well documented, and the principal mechanisms have been defined. Bypass metabolism, such as alternative oxidoreductases, have been discovered in both organisms. Aerobic versus anaerobic resistance in T. vaginalis is discussed. Mechanisms of metronidazole resistance in E. histolytica have recently been investigated using laboratory-induced resistant isolates. Instead of downregulation of the pyruvate:ferredoxin oxidoreductase and ferredoxin pathway as seen in G. duodenalis and T. vaginalis, E. histolytica induces oxidative stress mechanisms, including superoxide dismutase and peroxiredoxin. The review examines the value of investigating both clinical and laboratory-induced syngeneic drug-resistant isolates and dissection of the complementary data obtained. Comparison of resistance mechanisms in anaerobic bacteria and the parasitic protozoa is discussed as well as the value of studies of the epidemiology of resistance

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Asymptomatic Intestinal Colonization by Pathogenic Entamoeba histolytica in Amebic Liver Abscess: Prevalence, Response to Therapy, and Pathogenic Potential

Cited by 92 publications

References 24 publications

Real-Time PCR for Detection and Differentiation ofEntamoeba histolyticaandEntamoeba disparin Fecal Samples

Real-Time PCR for Detection and Differentiation ofEntamoeba histolyticaandEntamoeba disparin Fecal Samples

Differentiation of entamoeba histolytica/entamoeba dispar by PCR and their correlation with humoral and cellular immunity in individuals with clinical variants of amoebiasis.

Drug Targets and Mechanisms of Resistance in the Anaerobic Protozoa

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