Increased sampling reveals novel lineages of Entamoeba: consequences of genetic diversity and host specificity for taxonomy and molecular detection.

To expand the representation for phylogenetic analysis, ten additional complete Entamoeba small-subunit rRNA gene sequences were obtained from humans, non-human primates, cattle and a tortoise. For some novel sequences no corresponding morphological data were available, and we suggest that these organisms should be referred to as ribosomal lineages (RL) rather than being assigned species names at present. To investigate genetic diversity and host specificity of selected Entamoeba species, a total of 91 new partial small subunit rRNA gene sequences were obtained, including 49 from Entamoeba coli, 18 from Entamoeba polecki, and 17 from Entamoeba hartmanni. We propose a new nomenclature for significant variants within established Entamoeba species. Based on current data we propose that the uninucleated-cyst-producing Entamoeba infecting humans is called Entamoeba polecki and divided into four subtypes (ST1-ST4) and that Entamoeba coli is divided into two subtypes (ST1-ST2). New hosts for several species were detected and, while host specificity and genetic diversity of several species remain to be clarified, it is clear that previous reliance on cultivated material has given us a misleading and incomplete picture of variation within the genus Entamoeba

Clonación y análisis de la estructura primaria de quitina sintasas de entamoeba histolytica: perfil de expresión durante el enquistamiento

Entamoeba histolytica, parásito responsable de la amibiasis, presenta dos etapas en su ciclo de vida: trofozoíto y quiste. Los quistes (forma infectiva) poseen una pared compuesta principalmente por quitina, polímero de ß-(1→4)-N-acetil-Dglucosamina cuya síntesis es catalizada por quitina sintasas (CHS). Las CHS se han descrito en hongos, insectos y nemátodos, pero no en protozoarios como Entamoeba. Se clonaron y secuenciaron dos genes CHS de E. histolytica. Se determinó que ambas EhCHS contienen segmentos transmembranales en sus extremos, y que la mayor similitud está restringida a la «región catalítica»; los aminoácidos importantes para la actividad de CHS están completamente conservados en ambas EhCH

Experimental transmission of Zika virus by mosquitoes from central Europe

Mosquitoes collected in Germany in 2016, including Culex pipiens pipiens biotype pipiens, Culex torrentium and Aedes albopictus, as well as Culex pipiens pipiens biotype molestus (in colony since 2011) were experimentally infected with Zika virus (ZIKV) at 18 degrees C or 27 degrees C. None of the Culex taxa showed vector competence for ZIKV. In contrast, Aedes albopictus were susceptible for ZIKV but only at 27 degrees C, with transmission rates similar to an Aedes aegypti laboratory colony tested in parallel.Peer reviewe

Outbreak of cryptosporidium hominis following river flooding in the city of Halle (Saale), Germany, August 2013

Background: During weeks 32–33, 2013, 24 cases of cryptosporidiosis were notified in the city of Halle (annual mean 2008–2012: 9 cases). We investigated the outbreak to identify the source and recommend control measures, considering that between weeks 23–25 the river Saale which flows through the city centre overflowed the floodplain, parts of the city centre and damaged sewage systems. Methods: We defined a case as a resident of Halle with gastroenteritis, Cryptosporidium-positive stool and disease onset weeks 27 through 47. In a case–control study among kindergarten children, we compared cases and controls regarding environmental exposure, use of swimming pools, zoo visits and tap water consumption 14 days pre-onset or a corresponding 14-days-period (controls) and adjusted for residence. Stool specimens were tested by microscopy and PCR, and Cryptosporidium DNA was sequenced. Samples from public water system, swimming pools and river Saale were examined for Cryptosporidium oocysts (microscopy and PCR). Results: Overall, 167 cases were detected, 40/167 (24%) were classified as secondary cases. First disease onsets occurred during week 29, numbers peaked in week 34 and started to decrease in week 36. Median age was 8 years (range: 0–77). Compared to controls (n = 61), cases (n = 20) were more likely to report visits to previously flooded areas (OR: 4.9; 95%-CI: 1.4-18) and the zoo (OR: 2.6; 95%-CI: 0.9-7.6). In multivariable analysis visits to the floodplain remained the sole risk factor (OR: 5.5; 95%-CI: 1.4-22). Only C.hominis of a single genotype (IbA9G2) was detected in stools. Oocysts were detected in samples from the river, two local lakes and three public swimming pools by microscopy, but not in the public water supply. Conclusions: Evidence suggests that activities in the dried out floodplain led to infection among children. Secondary transmissions may be involved. Consequently, authorities recommended to avoid playing, swimming and having picnics in the flood-affected area. Health authorities should consider the potential health risks of long-term surviving parasites persisting on flooded grounds and in open waters even several weeks after the flooding and of bathing places close to sewage spill-overs. Preventive measures comprise water sampling (involving parasites), information of the public and prolonged closures of potentially contaminated sites

Host tissue destruction by Entamoeba histolytica: molecules mediating adhesion, cytolysis, and proteolysis

Entamoeba histolytica, the protozoan parasite causing human amoebisis, has recently been found to comprise two genetically distinct forms, potentially pathogenic and constitutively nonpathogenic ones. Host tissue destruction by pathogenic forms is belived to result from cell functions mediaed by a lectin-type adherence receptor, a pore-forming peptide involved in host cell lysis, and abundant expression of cysteine proteinase(s). Isolation and molecular cloning of these amoeba products have provided the tools for structural analyses and manipulations of cell functions including comparisons between pathogenic and nonpathogenic forms

Absence of Erythrocyte Sequestration and Lack of Multicopy Gene Family Expression in Plasmodium falciparum from a Splenectomized Malaria Patient

BACKGROUND:To avoid spleen-dependent killing mechanisms parasite-infected erythrocytes (IE) of Plasmodium falciparum malaria patients have the capacity to bind to endothelial receptors. This binding also known as sequestration, is mediated by parasite proteins, which are targeted to the erythrocyte surface. Candidate proteins are those encoded by P. falciparum multicopy gene families, such as var, rif, stevor or PfMC-2TM. However, a direct in vivo proof of IE sequestration and expression of multicopy gene families is still lacking. Here, we report on the analysis of IE from a black African immigrant, who received the diagnosis of a malignant lymphoproliferative disorder and subsequently underwent splenectomy. Three weeks after surgery, the patient experienced clinical falciparum malaria with high parasitemia and circulating developmental parasite stages usually sequestered to the vascular endothelium such as late trophozoites, schizonts or immature gametocytes. METHODOLOGY/PRINCIPAL FINDINGS:Initially, when isolated from the patient, the infected erythrocytes were incapable to bind to various endothelial receptors in vitro. Moreover, the parasites failed to express the multicopy gene families var, A-type rif and stevor but expression of B-type rif and PfMC-2TM genes were detected. In the course of in vitro cultivation, the parasites started to express all investigated multicopy gene families and concomitantly developed the ability to adhere to endothelial receptors such as CD36 and ICAM-1, respectively. CONCLUSION/SIGNIFICANCE:This case strongly supports the hypothesis that parasite surface proteins such as PfEMP1, A-type RIFIN or STEVOR are involved in interactions of infected erythrocytes with endothelial receptors mediating sequestration of mature asexual and immature sexual stages of P. falciparum. In contrast, multicopy gene families coding for B-type RIFIN and PfMC-2TM proteins may not be involved in sequestration, as these genes were transcribed in infected but not sequestered erythrocytes

Differences in the transcriptome signatures of two genetically related Entamoeba histolytica cell lines derived from the same isolate with different pathogenic properties

<p>Abstract</p> <p>Background</p> <p>The availability of two genetically very similar cell lines (A and B) derived from the laboratory isolate <it>Entamoeba histolytica </it>HM-1:IMSS, which differ in their virulence properties, provides a powerful tool for identifying pathogenicity factors of the causative agent of human amoebiasis. Cell line A is incapable inducing liver abscesses in gerbils, whereas interaction with cell line B leads to considerable abscess formation. Phenotypic characterization of both cell lines revealed that trophozoites from the pathogenic cell line B have a larger cell size, an increased growth rate <it>in vitro</it>, an increased cysteine peptidase activity and higher resistance to nitric oxide stress. To find proteins that may serve as virulence factors, the proteomes of both cell lines were previously studied, resulting in the identification of a limited number of differentially synthesized proteins. This study aims to identify additional genes, serving as virulence factors, or virulence markers.</p> <p>Results</p> <p>To obtain a comprehensive picture of the differences between the cell lines, we compared their transcriptomes using an oligonucleotide-based microarray and confirmed findings with quantitative real-time PCR. Out of 6242 genes represented on the array, 87 are differentially transcribed (≥two-fold) in the two cell lines. Approximately 50% code for hypothetical proteins. Interestingly, only 19 genes show a five-fold or higher differential expression. These include three <it>rab7 GTPases</it>, which were found with a higher abundance in the non-pathogenic cell line A. The <it>aig1-like GTPases</it>are of special interest because the majority of them show higher levels of transcription in the pathogenic cell line B. Only two molecules were found to be differentially expressed between the two cell lines in both this study and our previous proteomic approach.</p> <p>Conclusions</p> <p>In this study we have identified a defined set of genes that are differentially transcribed between the non-pathogenic cell line A and the pathogenic cell line B of <it>E. histolytica</it>. The identification of transcription profiles unique for amoebic cell lines with pathogenic phenotypes may help to elucidate the transcriptional framework of <it>E. histolytica </it>pathogenicity and serve as a basis for identifying transcriptional markers and virulence factors.</p