In vitro Antiplasmodial Activity and Cytotoxicity of Vincadifformine and Its Semisynthetic Derivatives

An indole alkaloid with aspidospemane structure possessing a potential antiplasmodial activity, vincadifformine, has been isolated from Aspidosperma pyrifolium Mart. Moreover, 10 derivatives were prepared from the vincadifformine. The study was conducted to evaluate the in vitro antiplasmodial and cytotoxic activity of the vincadifformine and their semisynthetic derivatives. The in vitro antiplasmodial activity was evaluated on Plasmodium falciparum chloroquine-resistant (FcM29) and –sensitive (Nigerian) strains after 24-h and 72-h incubation, while cytotoxic activity was estimated on Hela cells and Cytotoxicity Index (CI = IC50  on HeLa cells/IC50 on FcM29  strain) was calculated to evaluate the safety of tested compounds. Experiment results showed that two compounds (4 and 8) exhibited good antiplasmodial activities in comparison with parent compound, vincadifformine and other tested compounds with IC50   ranging from 5.3 to 12.8 µM on FcM29   strain and 11.4 to 24.0 µM on Nigerian strain. In addition, the CI of two compounds were also lower after 24-h incubation (CI, 2.0 and 4.8) than that of after 72-h incubation (CI, 9.5 and 11.5). Further study will be conducted to evaluate quantitative structure-activity relationship (QSAR) in order to design new antimalarial drugs

In vitro Antiplasmodial Activity and Cytotoxicity of Vincadifformine and Its Semisynthetic Derivatives

An indole alkaloid with aspidospemane structure possessing a potential antiplasmodial activity,vincadifformine, has been isolated from Aspidosperma pyrifolium Mart. Moreover, 10 derivatives were preparedfrom the vincadifformine. The study was conducted to evaluate the in vitro antiplasmodial and cytotoxic activity ofthe vincadifformine and their semisynthetic derivatives. The in vitro antiplasmodial activity was evaluated onPlasmodium falciparum chloroquine-resistant (FcM ) and –sensitive (Nigerian) strains after 24-h and 72-h incubation, 29while cytotoxic activity was estimated on Hela cells and Cytotoxicity Index (CI = IC on HeLa cells/IC on FcM strain) 50 50 29was calculated to evaluate the safety of tested compounds. Experiment results showed that two compounds (4 and 8)exhibited good antiplasmodial activities in comparison with parent compound, vincadifformine and other testedcompounds with IC ranging from 5.3 to 12.8 μM on FcM strain and 11.4 to 24.0 μM on Nigerian strain. In addition, 50 29the CI of two compounds were also lower after 24-h incubation (CI, 2.0 and 4.8) than that of after 72-h incubation (CI,9.5 and 11.5). Further study will be conducted to evaluate quantitative structure-activity relationship (QSAR) in orderto design new antimalarial drugs.Keywords : vincadifformine - antiplasmodial – Plasmodium falciparum – cytotoxic - HeL

The yeast Candida albicans has a clonal mode of reproduction in a population of infected human immunodeficiency virus-positive patients

To ascertain the population structure of Candida albicans, we have carried out a multilocus enzyme electrophoresis study based on the analysis of 21 gene loci. We have thus characterized 55 strains isolated one each from 55 human immunodeficiency virus-positive patients. There is considerable polymorphism among the strains. A population-genetic analysis indicates that the two fundamental consequences of sexual reproduction (i.e., segregation and recombination) are apparently absent in this population of C. albicans. The population structure of C. albicans appears to be clonal, a state of affairs that has important medical and biological consequences

Genetic Multilocus Studies of Different Strains of Cryptococcus neoformans: Taxonomy and Genetic Structure

The genotypes of 107 strains of Cryptococcus isolated from the environment or from patients from various geographical areas were determined by multilocus enzyme electrophoresis (MLEE). We analyzed the relationships between genotype structure and serotype and between genotype structure and strain origin. Twelve of the 14 enzyme-encoding loci studied were polymorphic, giving rise to 48 electrophoretic types. The genotypes of C. neoformans and C. laurentii were very similar. MLEE could not distinguish between these two pathogenic species. A correlation between the genetic multilocus structure and the origin of the sample (from the environment or patients) existed. A second analysis detected a correlation between genotype distribution and serotype. The second analysis considered three serotype groups (B, C, and A plus D plus A/D), proving that serotypes A, D, and A/D are closely related. MLEE is a useful epidemiological tool for improving our understanding of the biology of this fungus

Genetic Structure of Candida glabrata Populations in AIDS and Non-AIDS Patients

The genotypes of 63 strains (11 reference strains and 52 strains from hospitalized patients) of the haploid yeast Candida glabrata were determined from 33 putative gene enzymatic loci. This enabled the characterization of 26 different multilocus genotypes. Genetic differentiation was found between distant hospitals (located in Montpellier and Paris, France) but not for other parameters (anatomic origins or human immunodeficiency virus-positive [HIV(+)] and HIV(−) patients). Strong nonrandom association between loci could be seen. Such statistical linkages were confirmed upon comparing the patterns of 14 RAPD [random(ly) amplified polymorphic DNA] primers from 20 of these strains to results obtained from multilocus enzyme electrophoresis analysis. This finding suggests a mainly clonal mode of reproduction of C. glabrata. The consequences of the clonality displayed by C. glabrata populations on the epidemiology of this yeast are also discussed

Interlaboratory Reproducibility of Etest Amphotericin B and Caspofungin Yeast Susceptibility Testing and Comparison with the CLSI Method

International audiencee This study aimed to assess the interlaboratory reproducibility at four university hospital laboratories in the southeast region of France of the Etest technique for the determination of caspofungin (CAS) and amphotericin B (AMB) MICs and to compare it to the CLSI broth microdilution reference method. Consecutive clinical yeast isolates (n ‫؍‬ 198) were included in the study. AMB and CAS MICs were read at 24 and 48 h. Interlaboratory reproducibility was estimated by using (i) an intraclass correlation coefficient (ICC), (ii) essential agreement (EA), and (iii) categorical agreement (CA). For Etest interlaboratory reproducibility for CAS, ICCs were 0.80 (95% confidence interval [CI], 0.76 to 0.84) and 0.81 (95% CI, 0.77 to 0.85) at 24 and 48 h, respectively. For AMB, the ICCs were 0.51 (95% CI, 0.43 to 0.58) and 0.69 (95% CI, 0.63 to 0.74) at 24 and 48 h, respectively. At 48 h, the between-center EAs ranged from 94.4 to 99.0% for both antifungals. For the comparison of the CLSI method and the Etest, the between-technique ICCs were 0.69 (95% CI, 0.63 to 0.74) and 0.62 (95% CI, 0.55 to 0.68) for CAS and AMB, respectively. The EAs ranged from 76.5 to 98.5% for CAS and from 90.3 to 97.4% for AMB according to the centers. CAs ranged from 87.9% to 91.4%, with four very major errors for 2 strains (1 Candida albicans strain and 1 Candida krusei strain), for CAS and from 97.5 to 99.5%, with four major errors, for AMB. In conclusion, the Etest showed a good interlaboratory reproducibility and a good correlation with the CLSI technique. It is well suited for the routine clinical laboratory and can thus be used to monitor clinical yeast iso-lates' in vitro susceptibilities in this setting. S ince the 1990s, knowledge about the diversity of yeast species involved in human infections, the incidence of drug-resistant isolates, and antifungal drug resistance mechanisms has significantly increase (6, 10, 16, 24). In vitro susceptibility tests are based on the measurement of growth with different drug concentrations so as to determine the MIC for the population of a given isolate, an in vitro-determined value that helps predict therapeutic efficacy (1). This has been achieved with some degree of confidence by using in vivo models to determine clinical breakpoints in invasive yeast infections, providing a useful indicator to guide therapeutic choices (20). The reference tests for susceptibility testing are the broth microdilution assays devised by the Clinical and Laboratory Standards Institute (CLSI) and by the European Committee on Antibiotic Susceptibility Testing (EUCAST) (5, 23). These reference methods are robust and reproducible; however, they remain time-consuming and poorly suited for the routine clinical laboratory setting. Moreover, the MIC values for amphotericin B are tightly clustered, and these methods rarely detect MIC values above 1 mg/liter (2). To overcome these limitations, many commercially available methods, such as the Etest, Sensititre Yeast-One, or disk diffusion methods, that are easy to use in the routine setting have been developed. These methods have been recently incorporated into routine clinical laboratory practice and thus generate a considerable amount of antifungal MIC data from clinical fungal isolates. Presently, the monitoring of antifungal drug susceptibility is usually restricted to national reference laboratories that use broth microdilution assays to test clinical isolates referred from collaborating clinical laboratories. These laboratories thus collect invaluable data for the monitoring of susceptibility trends on national and international scales. However, there is a need to develop antifungal susceptibility monitoring at a local or regional scale. This complementary approach to the national reference centers could also improve patient care and generate significant cost reductions given the prevalence of yeast infections, their morbidity, and the costly protracted treatments required. As a first step toward setting up a regional survey of in vitro antifungal susceptibility in the southeast region of France, the primary aim of the present study was to assess the interlaboratory reproducibility of MICs determined with the commercially available and routinely used Etest method for yeast isolated in first-line clinical mycology laboratories of the four regional teaching hospitals. The secondary aims were to validate the correlation of the MICs of amphotericin B and caspofungin obtained with the Etest and CLSI assays at 24 h and 48 h

Cryptoccocal meningitis in Yaoundé (Cameroon) HIV infected patients: Diagnosis, frequency and Cryptococcus neoformans isolates susceptibility study to fluconazole

International audienceCryptococcal meningitis is a mycosis encountered especially in patients with Acquired Immunodeficiency Syndrome and is fatal in the absence of treatment. Information on epidemiology, diagnosis and susceptibility profile to antifungal drugs, are scarce in Cameroon. Authors evaluated the diagnosis possibilities of the cryptococcal meningitis in Cameroon, and studied the antifungal susceptibility of isolated strains to fluconazole, used as first line treatment of the disease in Cameroon. Between December 2009 and July 2011, 146 cerebrospinal fluids obtained from HIV patients with suspicion of meningitis were analysed. The diagnosis procedure involved macroscopic and cyto-chemical analysis, India ink test, culture on Sabouraud chloramphenicol medium and antigen latex agglutination test. Antifungal susceptibility testing of isolated strains to fluconazole was done by the E-test(®) method. The diagnosis of cryptococcal meningitis gave 28.08% positive cases. Among these patients, 80% were at stages III and IV and 20% at stage I of the HIV infection, according to the WHO previous classification. Cyto-chemical analysis showed current findings in the case of cryptococcal meningitis. India ink test and latex agglutination test exhibited very high sensitivity and specificity (>94%). Fluconazole antifungal susceptibility testing gave MICs lower than 32μg/mL to 92.7% of isolated strains and MICs greater than this value to 7.3% of isolates. These results showed that cryptococcal meningitis remains a real problem among HIV infected patients in Yaoundé. The emergence of fluconazole reduced susceptibility strains is worrying. Nevertheless, efficacy of rapid detection tests is interesting because this will help in rapid diagnosis and treatment of patients