Inhibition of growth of Pneumocystis carinii by lactoferrins alone and in combination with pyrimethamine, clarithromycin and minocycline. (1/765)

The in vitro activity of lactoferrins alone and in combination with clarithromycin, minocycline and pyrimethamine was investigated against three clinical isolates of Pneumocystis carinii. Susceptibility was tested by inoculating isolates on to cell monolayers and determining the parasite count after 72 h incubation at 37 degrees C. The culture medium was supplemented with serial dilutions of each agent. At 20 mg/L, bovine lactoferrin, the most active agent, suppressed the growth of cystic and trophic forms by >60%. Human lactoferrin, at the same concentration, suppressed the growth of cystic and trophic forms by >50%. Lactoferrins at 20 mg/L combined with clarithromycin 4 mg/L had high anti-P. carinii activity, with a >90% decrease in cystic and trophic form counts. Our study suggests that lactoferrins may inhibit P. carinii growth in vitro and act synergically with other clinically used compounds. These findings lend experimental support to the use of iron-chelating agents in the therapy of pneumocystis infections.  (+info)

Contribution of dithiol ligands to in vitro and in vivo trypanocidal activities of dithiaarsanes and investigation of ligand exchange in an aqueous solution. (2/765)

Twelve new dithiaarsanes were evaluated for their in vitro and in vivo trypanocidal properties in regard to their three parent molecules, 4-amino-phenylarsenoxide, melarsenoxide, and 4-dansylamino-phenylarsenoxide. The most potent dithiaarsane, compound 2b, had a minimum effective concentration of 1.5 nM after 48 h of incubation and at a dose of 0.39 micromol/kg of body weight (0.2 mg/kg) administered subcutaneously cured 100% of mice acutely infected with Trypanosoma brucei brucei CMP. With this model, the chemotherapeutic index of compound 2b was 512, compared to 256 for melarsamine dihydrochloride (Cymelarsan) under the same conditions. With a chronic infection produced by T. brucei brucei GVR, compound 2b cured 100% of mice after treatment at a dose of 25 micromol/kg (12.5 mg/kg) for 4 consecutive days, whereas melarsamine dihydrochloride and potassium melarsonyl (Trimelarsan) cured less than 50% mice at this dose. For both acute and late-stage infections, dithiaarsanes having a melaminophenyl ring exhibited the most-potent trypanocidal activity. Compound 2b is thus one of the most active organoarsenicals described in a mouse trypanosomiasis model. Considering that the main intracellular targets of organoarsenicals are thiol groups, we studied the possibility of ligand exchange between Cymelarsan and several dithiols. In aqueous solution, we observed a rapid exchange of cysteamine from melarsamine with free cysteamine and also with various dithiols always in favor of more stable cyclic derivatives. These ligand exchanges suggest the ability of trivalent organoarsenicals to react with targets such as trypanothione and dihydrolipoic acid. Among several ligands, a 1,3-dimercaptopropane moiety appeared the most suitable for trypanocidal activity.  (+info)

In vitro efficacy of nikkomycin Z against the human isolate of the microsporidian species Encephalitozoon hellem. (3/765)

Since 1985 microsporidia have been recognized as a cause of emerging infections in humans, mainly in immunocompromised human immunodeficiency virus-positive subjects. As chitin is a basic component of the microsporidian infective stage, the spore, we evaluated in vitro the susceptibility of a human-derived strain of Encephalitozoon hellem to nikkomycin Z, a peptide-nucleoside antibiotic known as a competitive inhibitor of chitin synthase enzymes. Transmission electron microscopy showed that this drug, at 25 microgram/ml, reduced the number of parasitic foci by about 35% +/- standard deviation after 7 days of culture (P < 0.0001) and induced cell damage of both mature and immature spores and also other sporogonic and merogonic stages. In particular, an irregular outline of the cell shape and an abnormally condensed cytoplasm in meronts and sporonts were documented. Also, the polar tubule and the polaroplast membranes appeared disarrayed in the sporoblast stage. The spore wall showed an enlarged endospore and delaminated exospore. Mature spores had a complete cytoplasmic disorganization and a swollen and delaminated cell wall. No ultrastructural cell damage was observed in uninfected control cultures treated with the drug.  (+info)

Flow cytometric detection of Leishmania parasites in human monocyte-derived macrophages: application to antileishmanial-drug testing. (4/765)

A flow cytometric technique was developed for detection of amastigotes of the protozoan Leishmania infantum in human nonadherent monocyte-derived macrophages. The cells were fixed and permeabilized with paraformaldehyde-ethanol, and intracellular amastigotes were labeled with Leishmania lipophosphoglycan-specific monoclonal antibody. Results showed that flow cytometry provided accurate quantification of the infection rates in human macrophages compared to the rates obtained by the conventional microscopic technique, with the advantage that a large number of cells could be analyzed rapidly. The results demonstrated, moreover, that labeling of intracellular amastigotes could reliably be used to evaluate the antileishmanial activities of conventional drugs such as meglumine antimoniate, amphotericin B, pentamidine, and allopurinol. They also established that various Leishmania species (L. mexicana, L. donovani) could be detected by this technique in other host-cell models such as mouse peritoneal macrophages and suggested that the flow cytometric method could be a valid alternative to the conventional method.  (+info)

Gametocytocidal activity and synergistic interactions of riboflavin with standard antimalarial drugs against growth of Plasmodium falciparum in vitro. (5/765)

Our previous studies have shown that riboflavin has activity against Plasmodium falciparum asexual-stage parasites in vitro. In the present study we examine the gametocytocidal activity of riboflavin and the interaction of riboflavin with some commonly used antimalarial drugs against the asexual forms of P. falciparum in vitro. The addition of riboflavin to P. falciparum cultures killed gametocytes at all stages, even those at late stages (III to V), which are not affected by many of the commonly used antimalarials. Combinations of riboflavin with mefloquine, pyrimethamine, and quinine showed a marked potentiation of the activities of these drugs against asexual-stage parasites in vitro. The combination of riboflavin with artemisinin was additive, while that with chloroquine was mildly antagonistic. High doses of riboflavin are used clinically to treat several inborn errors of metabolism with no adverse side effects. Its efficacy in combination with standard antimalarial drugs in treating and preventing the transmission of P. falciparum malaria can therefore be evaluated in humans.  (+info)

The changing in vitro susceptibility pattern to pyrimethamine/sulfadoxine in Plasmodium falciparum field isolates from Kilifi, Kenya. (6/765)

Two clinical trials that used Falcidin (Cosmos Ltd., Nairobi, Kenya), the antifolate combination of pyrimethamine/sulfadoxine (PM/SD), as treatment for non-severe falciparum malaria in children at Kilifi, Kenya in 1987-1988 and 1993-1995 have presented an opportunity to assess in vitro the susceptibility trend of Plasmodium falciparum to PM and SD over time on the Kenya coast. The first set of isolates was collected prior to the introduction of PM/SD into the Kenya Medical Research Institute/Wellcome Trust Research unit while the second set was taken soon after PM/SD was introduced in the study area as the first-line treatment drug for uncomplicated falciparum malaria. In the first trial, 69 isolates collected before and after treatment of malaria with PM/SD were tested directly in the field for susceptibility to PM and SD using the standard in vitro micro-test technique, with minimal levels of folate. In the second trial, 97 isolates similarly collected were adapted to culture, and tested as described elsewhere. In both studies, PM and SD susceptibility tests were done separately. There was a highly significant decrease (P < 0.01) in the in vitro sensitivity of P. falciparum isolates to PM and SD between the two trials. In the first trial, the isolates were either sensitive to both PM and SD or resistant to PM and sensitive to SD. During the second trial, isolates were either resistant to PM and sensitive to SD or resistant to both drugs. These results are important in estimating the useful therapeutic life (UTL) of PM/SD in this area and in identifying alternative antifolate drugs.  (+info)

Microbial and chemical conversion of antibiotic K41. II. Preparation of K41-DA1, -DA2 and -DA3 deamicetosyl derivatives of antibiotic K41. (7/765)

Antibiotic derivative K41-DA1, -DA2 and -DA3 (2 approximately 4), deamicetosyl derivatives of antibiotic K41 (1), were prepared by acidic degradation of K41 and following hydrogenation reaction. K41-DA2 (3) showed comparable antimicrobial activities to K41 in vitro but not in vivo.  (+info)

Plasmodium falciparum malaria in Laos: chloroquine treatment outcome and predictive value of molecular markers. (8/765)

A 28-day treatment trial was undertaken, to determine the efficacy of chloroquine in Laos and to assess the predictive value of molecular markers (cg2, pfmdr1, and pfcrt) that were previously linked to chloroquine resistance. In total, 522 febrile patients were screened for falciparum malaria by rapid diagnostic assays. Of 81 patients (15.5% prevalence) who were positive by the assays and microscopy, 48 were eligible to participate in the 28-day trial. Nine patients defaulted. Chloroquine cured 54% (95% confidence interval, 45.8-61.8) of falciparum-infected patients. Of 18 (46%) patients with treatment failure, 13 (72%) experienced high-grade resistance. Polymorphisms in cg2 and the N86Y mutation in PfMDR1 were not predictive of treatment outcome. A mutation in PfCRT (K76T) was perfectly associated with in vivo chloroquine resistance. However, K76T was also present in in vivo-sensitive isolates, which suggests that the presence of this mutation was necessary, but not sufficient, to predict in vivo outcome in this cohort.  (+info)