Prozone in malaria rapid diagnostics tests: how many cases are missed?

<p>Abstract</p> <p>Background</p> <p>Prozone means false-negative or false-low results in antigen-antibody reactions, due to an excess of either antigen or antibody. The present study prospectively assessed its frequency for malaria rapid diagnostic tests (RDTs) and <it>Plasmodium falciparum </it>samples in an endemic field setting.</p> <p>Methods</p> <p>From January to April 2010, blood samples with <it>P. falciparum </it>high parasitaemia (≥ 4% red blood cells infected) were obtained from patients presenting at the Provincial Hospital of Tete (Mozambique). Samples were tested undiluted and 10-fold diluted in saline with a panel of RDTs and results were scored for line intensity (no line visible, faint, weak, medium and strong). Prozone was defined as a sample which showed no visible test line or a faint or weak test line when tested undiluted, and a visible test line of higher intensity when tested 10-fold diluted, as observed by two blinded observers and upon duplicate testing.</p> <p>Results</p> <p>A total of 873/7,543 (11.6%) samples showed <it>P. falciparum</it>, 92 (10.5%) had high parasitaemia and 76 were available for prozone testing. None of the two Pf-pLDH RDTs, but all six HRP-2 RDTs showed prozone, at frequencies between 6.7% and 38.2%. Negative and faint HRP-2 lines accounted for four (3.8%) and 15 (14.4%) of the 104 prozone results in two RDT brands. For the most affected brand, the proportions of prozone with no visible or faint HRP-2 lines were 10.9% (CI: 5.34-19.08), 1.2% (CI: 0.55-2.10) and 0.1% (CI: 0.06-0.24) among samples with high parasitaemia, all positive samples and all submitted samples respectively. Prozone occurred mainly, but not exclusively, among young children.</p> <p>Conclusion</p> <p>Prozone occurs at different frequency and intensity in HRP-2 RDTs and may decrease diagnostic accuracy in the most affected RDTs.</p

Sugar Levels Determine Fermentation Dynamics during Yeast Pastry Making and Its Impact on Dough and Product Characteristics

Fermented pastry products are produced by fermenting and baking multi-layered dough. Increasing our knowledge of the impact of the fermentation process during pastry making could offer opportunities for improving the production process or end-product quality, whereas increasing our knowledge on the sugar release and consumption dynamics by yeast could help to design sugar reduction strategies. Therefore, this study investigates the impact of yeast fermentation and different sugar concentrations on pastry dough properties and product quality characteristics. First, yeasted pastry samples were made with 8% yeast and 14% sucrose on a wheat flour dry matter base and compared to non-yeasted samples. Analysis of saccharide concentrations revealed that sucrose was almost entirely degraded by invertase in yeasted samples after mixing. Fructans were also degraded extensively, but more slowly. At least 23.6 ± 2.6% of the released glucose was consumed during fermentation. CO2 production during fermentation contributed more to product height development than water and ethanol evaporation during baking. Yeast metabolites weakened the gluten network, causing a reduction in dough strength and extensibility. However, fermentation time had a more significant impact on dough rheology parameters than the presence of yeast. In balance, yeast fermentation did not significantly affect the calculated sweetness factor of the pastry product with 14% added sucrose. Increasing the sugar content (21%) led to higher osmotic stress, resulting in reduced sugar consumption, reduced CO2 and ethanol production and a lower product volume. A darker colour and a higher sweetness factor were obtained. Reducing the sugar content (7%) had the opposite effect. Eliminating sucrose from the recipe (0%) resulted in a shortened productive fermentation time due to sugar depletion. Dough rheology was affected to a limited extent by changes in sucrose addition, although no sucrose addition or a very high sucrose level (21%) reduced the maximum dough strength. Based on the insights obtained in this study, yeast-based strategies can be developed to improve the production and quality of fermented pastry

Evaluation of the rapid diagnostic test CareStart pLDH Malaria (Pf-pLDH/pan-pLDH) for the diagnosis of malaria in a reference setting

BACKGROUND: The present study evaluated CareStart pLDH Malaria, a three-band rapid diagnostic test detecting Plasmodium falciparum-specific parasite lactate dehydrogenase (Pf-pLDH) and pan Plasmodium-specific pLDH (pan-pLDH) in a reference setting. METHODS: CareStart pLDH was retrospectively and prospectively assessed with a panel of stored (n = 498) and fresh (n = 77) blood samples obtained in international travelers suspected of malaria. Both panels comprised all four Plasmodium species; the retrospective panel comprised also Plasmodium negative samples. The reference method was microscopy corrected by PCR. The prospective panel was run side-to-side with OptiMAL (Pf-pLDH/pan-pLDH) and SDFK60 (histidine-rich protein-2 (HRP-2)/pan-pLDH). RESULTS: In the retrospective evaluation, overall sensitivity for P. falciparum samples (n = 247) was 94.7%, reaching 98.7% for parasite densities > 1,000/mul. Most false negative results occurred among samples with pure gametocytaemia (2/12, 16.7%) and at parasite densities [less than or equal to] 100/ul (7/12, 58.3%). None of the Plasmodium negative samples (n = 96) showed visible test lines. Sensitivities for Plasmodium vivax (n = 70), Plasmodium ovale (n = 69) and Plasmodium malariae (n = 16) were 74.3%, 31.9% and 25.0% respectively. Wrong species identification occurred in 10 (2.5%) samples and was mainly due to P. vivax samples reacting with the Pf-pLDH test line. Overall, Pf-pLDH test lines showed higher line intensities compared to the pan-pLDH lines (67.9% and 23.0% medium and strong line intensities for P. falciparum). In the prospective panel (77 Plasmodium-positive samples), CareStart pLDH showed higher sensitivities for P. falciparum compared to OptiMAL (p = 0.008), lower sensitivities for P. falciparum as compare to SDFK60 (although not reaching statistical significance, p = 0.08) and higher sensitivities for P. ovale compared to both OptiMAL (p = 0.03) and SDFK60 (p = 0.01). Inter-observer and test reproducibility were good to excellent. CONCLUSION: CareStart pLDH performed excellent for the detection of P. falciparum, well for P. vivax, but poor for P. ovale and P. malariae

EFFECT OF CONCHING ON PROCYANIDINS AND FUNCTIONAL PROPERTIES OF CHOCOLATE

Chocolate is a highly processed cocoa product known to be rich in flavonoids, compounds which have been long associated to both healthy and sensory properties. A multi-step process involving cocoa beans fermentation, drying, roasting, nib-grinding and refining, conching and tempering is implied in the production of chocolate.To our knowledge, scarce attention has been paid to the effect of conching on the procyanidins profile, on their polymerisation from monomers up to oligomers and polymers, as well as on the in vitro functional properties such as antiradical activity and reducing power. Two conching processes, characterized by different time/temperature combinations, a Long Time Conching (LTC) and a Short Time Conching (STC), were thus taken studied and the effect on flavan-3-ols monomers, on the degree of polymerization and on the in vitro functional properties of dark chocolates was studied. Procyanidin content was determined by HPLC analysis, while the total polyphenol index (TPI), the antiradical activity as well as the reducing power were evaluated by the reaction with the Folin–Ciocalteu reagent, the decolorization assays of the ABTS radical (TEAC) and the Ferric Reducing Antioxidant Power (FRAP) methods, respectively.The procyanidins content and profile were deeply affected by the different processing conditions: at the end of conching the STC-samples were characterized by a higher amount of monomers, compared to the LTC-ones which, in turn, resulted more polymerised as confirmed by the presence of P10 polymers. Both STC- and LTC conched products presented comparable TPI and FRAP values but products collected at different steps during the conching process, and in particular during LTC, showed a significant improvement of the radical scavenging properties. This result suggest the possibility to modulate the conching process in terms of time and temperature combination in order to improve the antioxidant activity of the final products.[...

Use of microbial communities for human and animal health

The present invention relates to a mixture of bacteria belonging to at least 6 or 7 different and specific bacterial species preferably for use to prevent or treat gastro-intestinal disorders. Preferably, said mixture of bacteria are grown together in a fermenter prior to administering said mixture to a subject in order to prevent or treat said disorder