A study of the spore wall of Encephalitozoon hellem was performed on thin sections, freeze-fracture, and deep-etched samples to obtain information on spore wall organization and composition. Our observations demonstrate that the spore wall is formed by an inner 30-35 nm electron-lucent endospore and an outer 25-30 nm electron-dense exospore. The exospore is a complex of three layers: an outer spiny layer, an electron-lucent intermediate lamina and an inner fibrous layer. Freeze-fracture and deep-etching techniques reveal that the intermediate lamina and the inner fibrous layer result from the different spatial disposition of the same 4-nm thick fibrils. In thin sections the endospore reveals a scattered electron-dense material that appears in the form of trabecular structures when analyzed in deep-etched samples. The presence of chitin in the exospore is discussed.

To develop an alternative genotyping tool, the genetic diversity of Encephalitozoon hellem was examined at the polar tube protein (PTP) locus. Nucleotide sequence analysis of the PTP gene divided 24 E. hellem isolates into four genotypes, compared to two genotypes identified by analysis of the internal transcribed spacer of the rRNA gene. The four PTP genotypes differed from each other by the copy number of the 60-bp central repeat as well as by point mutations. A simple PCR test was developed to differentiate E. hellem genotypes based on the difference in the size of PTP PCR products, which should facilitate the genotyping of E. hellem in clinical samples.

Twenty-two Italian HIV-infected patients developed leishmaniasis, clinically manifested as visceral (13 cases), cutaneous (2 cases) and disseminated disease (7 cases). Twenty were males and two females (mean age: 32.8 years) with a mean CD4+ cell count of 46.8/microliter at diagnosis; risk factors were intravenous drug use (17 patients) and sexual behaviour (two bisexual, two homosexual, one heterosexual). All but one patient lived or travelled in hypoendemic Italian regions and other Mediterranean countries. Apart from the two patients with cutaneous leishmaniasis, the clinico-pathological and biological spectrum of the infection was often atypical, especially in patients with disseminated disease. The diagnosis was routinely made by direct recovery of parasites in biological specimens, mainly in bone marrow aspirate, whereas serology was negative or borderline in most of the patients. Among 17 in vitro isolates, Leishmania infantum was the only species involved with previously undescribed isoenzyme patterns in two cases. Treatment with antimonials and other drugs showed only temporary clinical improvement in some patients. Relapses were the rule. Leishmaniasis confirms itself as an opportunistic infection in HIV-positive persons. Secondary chemoprophylaxis should be considered in cases of relapsing disease.

Abstract. An epidemiologic field study was conducted in the village of Borbòn in Esmeraldas province in northern Ecuador to compare different parasitologic methods in the diagnosis of infection with the Entamoeba histolytica/ Entamoeba dispar complex. The results of two stool antigen detection assays (the Prospect™ Entamoeba histolytica microplate assay and the E. histolytica II™ assay) were compared with isoenzyme characterization of the amebic isolates. Nearly all (176 of 178, 98.9%) subjects were positive for intestinal parasites on direct microscopic examination, and cysts and/or vegetative forms morphologically consistent with the E. histolytica/E .dispar complex were recorded in 48 of 178 cases (27%). Culture in Robinson's medium was positive for amebic stocks in 89 (50%) of the 178 samples tested. Of the 37 isolates successfully stabilized, cloned, and characterized by zymodeme analysis, seven (18.9%) showed isoenzyme patterns of E. histolytica, whereas 26 (70.3%) showed patterns of E. dispar. The remaining four strains were identified as Entamoeba coli (three isolates; 8.1%) and Dientamoeba fragilis (one strain; 2.7%).The immunochromatographic tests showed different degrees of sensitivity and specificity when compared with isoenzyme characterization as the reference technique. The microplate assay, which does not discriminate between E. histolytica and E.dispar, showed a sensitivity of 54.5% and a specificity of 94% for both these amebic species. In contrast, the second-generation E. histolytica II test had a sensitivity of 14.3% and a specificity of 98.4% for E. histolytica sensu stricto. Our survey clearly demonstrated that more specific and sensitive diagnostic tests, such as stool antigen detection assays and isoenzyme analysis, are needed to establish the actual worldwide distribution of E. histolytica and E. dispar.

We report the first case of primary amebic meningoencephalitis in Italy, in a 9-year-old boy. Clinical course was fulminant, and diagnosis was made by identifying amebas in stained brain sections and by indirect immunofluorescence analysis. Naegleria fowleri was characterized as genotype I on the basis of polymerase chain reaction test results.

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Malaria is a common, life-threatening infection in endemic tropical areas and one that presents a diagnostic challenge to laboratories in most non-endemic countries. A rapid and accurate diagnosis is a prerequisite for effective treatment, especially for the potentially fatal cases of Plasmodium falciparum infection. In the present, multi-centre study, the performances of a rapid diagnostic test (NOW) Malaria) and several, commercial, PCR-based assays (AMS61, AMS42, AMS43, AMS4 and AMS45) were compared against the results of microscopical examination of bloodsmears (the current 'gold standard'). The subjects were either non-European immigrants (N=135) or international travellers (N=171). There was good concordance between the results of all the detection methods, with kappa values of >0.8. Although the NOW Malaria rapid test was both sensitive (100%) and specific (100%) in detecting P. falciparum infections, it was less specific (93.1%) and sensitive (90.7%) in identifying the other Plasmodium species. The results from the AMS61 assay, designed to detect any malarial infection, generally parallelled those of the microscopy (kappa = 0.89), giving a specificity of 98.2% and a sensitivity of 91.0%. Although the use of species-specific molecular primers to identify pure infections with P. falciparum and P. vivax gave results that were in good agreement with those of the microscopy, the subjects who had apparently pure infections with P. ovale or P. malariae were always found PCR-negative. Compared with the standard microscopy, both the NOW Malaria test and the PCR-based assays were therefore poor at identifying mixed infections. The NOW Malaria test and the PCR-based assays clearly need to be improved, particularly for the correct identification of infections with Plasmodium spp. other than P. falciparum, including mixed infections. For now, expert microscopy must remain the mainstay of the laboratory diagnosis of malaria.

Acanthamoeba keratitis is a severe ocular infection secondary to accidental macro- or microscopic trauma of the cornea. Starting in 1985, a dramatic increase of this infection was recorded along with the spread of contact lens use. This protozoal disease is difficult to treat because of the scarcity of efficacious topical and systemic drugs. We evaluated the in vitro effectiveness of povidone-iodine (PVP-I [Betadine]), an agent with broad antibacterial and antiviral activity, compared to that of chlorhexidine (CXD), a cationic antiseptic, on Acanthamoeba isolates from patients with amebic keratitis. The results showed that PVP-I solution from 0.5 to 2.5% has a better antiamebic activity both on trophic and cystic stages of Acanthamoeba spp. than does CXD.