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Detection of fungal infections using radiolabeled antifungal agents
No full textThe outcome of antifungal therapy depends on the progression of the infection at the start of therapy. Unfortunately, most patients are diagnosed once the fungal infection has progressed considerably as a result of the non-specific clinical signs of fungal infections in immunocompromised patients and the poor sensitivity of current mycological diagnostic tests. This review will highlight current fungal diagnostic techniques and will focus on scintigraphic methods for the specific detection of fungal infections in mice. For this purpose, antifungal components (e.g. fluconazole and antifungal peptides) are radiolabeled e.g. with technetium-99m ((99m)Tc) and their in vivo distribution is monitored in infected mice. It has been demonstrated that (99m)Tc-fluconazole is an excellent tracer to detect Candida albicans infections in mice as it distinguishes these infections from bacterial infections and sterile inflammations. However, this radiopharmaceutical only poorly detects infections with Aspergillus fumigatus in mice. (99m)Tc-peptides derived from antifungal peptides/proteins, such as human ubiquicidin and lactoferrin, can distinguish C. albicans and A. fumigatus infections from sterile inflammations, but not from bacterial infections, in mice. Furthermore, the efficacy of fluconazole in C. albicans-infected mice could be successfully monitored using (99m)Tc-ubiquicidin. In conclusion, neither (99m)Tc-fluconazole nor the (99m)Tc-peptides tested are optimal tracers for fungal infections. Nonetheless, since early initiation of antifungal therapy for candidemia reduces its high mortality rate, a positive result with (99m)Tc-fluconazole scintigraphy is of clinical relevance. Finally, the possibility that other (radiolabeled) antifungal agents, e.g. voriconazole, caspofungin, antifungal plant or insect defensins, can be useful for detection of fungal infections should be considered
Radiochemical characteristics and biological testing of technetium-99m labelled antimicrobial cationic peptides for infection detection.
No full textRelease of calcium from intracellular stores and subsequent uptake by mitochondria are essential for the candidacidal activity of an N-terminal peptide of human lactoferrin
No full textOBJECTIVES:
Earlier studies showed that mitochondrial damage is a hallmark of the candidacidal activity of an N-terminal peptide of human lactoferrin, further referred to as hLF(1-11). Since uptake of Ca(2+) by mitochondria may be essential for their activation, the aim of this study was to define the role of Ca(2+) in killing of Candida albicans by the hLF(1-11) peptide.
METHODS:
The effect of compounds interfering with Ca(2+) homeostasis on the hLF(1-11)-induced candidacidal activity, changes in mitochondrial membrane potential, and reactive oxygen species production were evaluated using a killing assay, rhodamine 123 staining, and 2',7'-dichlorofluorescein diacetate, respectively. The increase in cellular Ca(2+) content was measured using (45)Ca(2+).
RESULTS:
Our results revealed that Ruthenium Red, which inhibits the mitochondrial Ca(2+)-uniporter and the voltage-sensitive Ca(2+) release from internal stores, blocked (P<0.05) the hLF(1-11)-induced candidacidal activity as well as changes in the membrane potential of mitochondria, and reactive oxygen species production. Oxalate, which precipitates Ca(2+) in intracellular organelles, decreased (P<0.05) the peptide-induced changes in the membrane potential of mitochondria, reactive oxygen species production, and candidacidal activity. Furthermore, the Ca(2+) ionophore ionomycin combined with high CaCl(2) concentrations enhanced the hLF(1-11)-induced candidacidal activity. Moreover, hLF(1-11) caused an influx of Ca(2+) from the extracellular medium into C. albicans reaching a three-fold increase at 2 h, whereas no increase was found in unexposed cells. In agreement, the Ca(2+)-chelator EGTA blocked the peptide-induced candidacidal activity.
CONCLUSIONS:
Ca(2+) release from intracellular stores, probably through subsequent mitochondrial Ca(2+) uptake, is essential for the hLF(1-11)-induced candidacidal activity
Infection detection in mice using 99mTc-labeled HYNIC and N2S2 chelate conjugated to the antimicrobial peptide UBI 29-41
No full textEarlier we reported that UBI 29-41, a synthetic peptide corresponding to residues 29-41 of human ubiquicidin, directly labeled with technetium-99m ((99m)Tc-UBI 29-41) distinguishes bacterial and fungal infections from sterile inflammations in animals. This study was undertaken to evaluate the radiochemical and biological characteristics of (99m)Tc-UBI 29-41 labeled through the intermediacy of a HYNIC or N(2)S(2) moiety, which were introduced at the N-terminus of UBI 29-41 during solid phase synthesis, with (99m)Tc-UBI 29-41. Methods were as follows: UBI 29-41 and HYNIC- or N(2)S(2)-conjugated peptide were labeled with technetium-99m. Preparations of these radiolabeled UBI 29-41 were purified by HPLC and Sep-Pak. Next, the stability of these tracers in human serum was challenged for 24 hours and their in vitro binding to bacteria assessed. Using scintigraphy up to 2 hours after injection of the tracer and ex vivo countings at the last interval we evaluated the ability of the three tracers to detect bacterial infections in mice inoculated with 2 x 10(7) viable Staphylococcus aureus or Klebsiella pneumoniae as well as their biodistribution. We observed the following results: HPLC analysis of purified (99m)Tc-HYNIC-UBI 29-41, (99m)Tc-UBI 29-41 and (99m)Tc-N(2)S(2)-UBI 29-41 revealed that within 60 minutes >90% of the radioactivity was associated with the peptide. In addition, the stability of these radiolabeled UBI 29-41 peptides in human serum was excellent. All three tracers bound equally well to bacteria in vitro. After intravenous injection into mice with an experimental bacterial infection (99m)Tc-HYNIC-UBI 29-41 and (99m)Tc-UBI 29-41 were rapidly removed from the circulation mainly by renal clearance (at t = 120 minutes approximately 60% of the injected dose/gram tissue; % ID/g). In contrast, (99m)Tc-N(2)S(2)-UBI 29-41 was removed mainly by the liver (t = 120 minutes; 52% ID/g) showing deposits in the intestines (t = 120 minutes; 31% ID/g) and to a lesser extent by renal clearance (19% ID/g). All three tracers rapidly detected bacterial infections in mice and highest accumulation (target-to-nontarget ratios between 3.2 and 3.6 and between 2.9 and 4.4 for infections with S. aureus and K. pneumoniae, respectively) was found at 2 hours after injection of the tracer. In conclusion, purified (99m)Tc-HYNIC-UBI 29-41 and (99m)Tc-N(2)S(2)-UBI 29-41 were as effective as (99m)Tc-UBI 29-41 in detecting infections in mice injected intramuscularly with bacteria. However, (99m)Tc-N(2)S(2)-UBI 29-41 should not be advised for the imaging of abdominal infections as this tracer, in contrast to the other tracers, is cleared via the liver and intestines
Imaging of fungal infections with 99mTc-labelled fluconazole and antimicrobial peptides.
No full textAntifungal effect of the antimicrobial peptide hLF(1-11) on invasive infections with Candida albicans.
No full textSaponin promotes rapid identification and antimicrobial susceptibility profiling of Gram-positive and Gram-negative bacteria in blood cultures with the Vitek 2 system
No full textThe rapid identification and antimicrobial susceptibility testing (AST) of bacteria in clinical blood cultures is crucial to optimise antimicrobial therapy. A previous study involving small sample numbers revealed that the addition of saponin to blood cultures, further referred to as the new method, shortened considerably the turn-around time for the identification and AST of Gram-positive cocci as compared to the current method involving an overnight subculture. Here, we extend previous results and compare the identification and AST of blood cultures containing Gram-negative bacilli by the new and current methods. The identification and AST of 121 Gram-positive and 109 Gram-negative bacteria in clinical monomicrobial blood cultures by the new and current methods and, in the case of Gram-negative bacilli, by direct (no additions) inoculation into an automated system (rapid method) was assessed using the Vitek 2 system. Discrepancies between the results obtained with the different methods were solved by manual methods. The new method correctly identified 88 % of Gram-positive and 98 % of Gram-negative bacteria, and the rapid method correctly identified 94 % of Gram-negative bacteria. The AST for all antimicrobials by the new method were concordant with the current method for 55 % and correct for an additional 9 % of Gram-positive bacteria, and concordant with the current method for 62 % and correct for an additional 21 % of Gram-negative bacilli. The AST by the rapid method was concordant with the current method for 62 % and correct for an additional 12 % of Gram-negative bacilli. Together, saponin-treated monomicrobial blood cultures allow rapid and reliable identification and AST of Gram-positive and Gram-negative bacteria
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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