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Drug Susceptibility (drug + susceptibility)
Selected AbstractsResampling-Based Multiple Testing Methods with Covariate Adjustment: Application to Investigation of Antiretroviral Drug SusceptibilityBIOMETRICS, Issue 2 2008Yang Yang Summary Identifying genetic mutations that cause clinical resistance to antiretroviral drugs requires adjustment for potential confounders, such as the number of active drugs in a HIV-infected patient's regimen other than the one of interest. Motivated by this problem, we investigated resampling-based methods to test equal mean response across multiple groups defined by HIV genotype, after adjustment for covariates. We consider construction of test statistics and their null distributions under two types of model: parametric and semiparametric. The covariate function is explicitly specified in the parametric but not in the semiparametric approach. The parametric approach is more precise when models are correctly specified, but suffer from bias when they are not; the semiparametric approach is more robust to model misspecification, but may be less efficient. To help preserve type I error while also improving power in both approaches, we propose resampling approaches based on matching of observations with similar covariate values. Matching reduces the impact of model misspecification as well as imprecision in estimation. These methods are evaluated via simulation studies and applied to a data set that combines results from a variety of clinical studies of salvage regimens. Our focus is on relating HIV genotype to viral susceptibility to abacavir after adjustment for the number of active antiretroviral drugs (excluding abacavir) in the patient's regimen. [source] Efficacies of caspofungin and a combination of caspofungin and meropenem in the treatment of murine disseminated candidiasis,APMIS, Issue 12 2006SEMA KECELI OZCAN Disseminated candidiasis is relatively common in immunocompromised patients. The treatment protocol of these patients usually includes broad-spectrum antibiotics and also emprical antifungals initiated due to unresponsiveness to antibiotics. In this study the efficacies of caspofungin and meropenem , separately and together , in mice with disseminated candidiasis were studied. Immunocompetent mice were infected intravenously with 2×106 CFU of Candida albicans. At 24 h postinfection, intraperitoneal therapy was initiated and was continued for 7 days. Therapy groups included those given caspofungin (0.5, 1.25, 5 mg/kg/day), meropenem (20 mg/kg/day), and a combination of the two drugs. The outcome of therapy was evaluated by kidney tissue burden studies and histologic examination. In vitro, drug susceptibilities were tested by checkerboard analysis. Kidney CFU counts showed that mice that had received both drugs had lower residual burdens. Caspofungin was effective at doses of 0.5, 1.25, 5 mg/kg compared to infected untreated controls. In vitro, MICs of caspofungin and meropenem were <0.075 ,g/ml and >64 ,g/ml, respectively. Synergism was observed with the combination. Histopathology showed that the degree of inflammation was 25% less and tubular necrosis was more restricted in combined therapy than monotherapy. The results indicate that concurrent caspofungin and meropenem therapy may be beneficial [source] Etiologic spectrum and pattern of antimicrobial drug susceptibility in bacterial meningitis in Sokoto, NigeriaACTA PAEDIATRICA, Issue 8 2000FE EmeleArticle first published online: 2 JAN 200 Etiologic agents of meningitis were prospectively investigated among patients admitted to Usman Danfodio University Teaching Hospital, Sokoto. Of 1097 cerebrospinal fluid (CSF) samples submitted to the microbiology laboratory from various wards of the hospital, 289 (26%) were microscopically, culturally and/or serologically proven to be bacterial meningitis. The etiologic spectrum was as follows: Neisseria meningitidis (61%), Streptococcus pneumoniae (18%), Haemophilus influenzae (10%), Staphylococcus aureus (6%), Coliform bacilli (3%), Escherichia coli (0.7%), Mycobacterium tuberculosis (0.7%), Listeria monocytogenes (0.4%), Flavobacterium meningosepticum (0.4%) and Pseudomonas putrifasciens (0.4%). Bacterial meningitis was most prevalent (195 or 68%) among children aged 1-9 y, while adults and neonates were least affected. Coliform bacilli caused five of eight neonatal cases. Males were more frequently affected than females (x2=12.50;p < 0.05). Culture and microscopy were comparatively less efficient than the search for bacterial antigens, especially in the diagnosis of Haemophilus meningitis. Antimicrobial susceptibility of N. meningitidis to ampicillin and benzyl penicillin reduced progressively over the years (F = 406.98;p < 0.001). Nineteen (11%) of the isolates (5 Meningococci, 7 Staph. aureus, 1 Haem. influenza and 6 others) showed simultaneous resistance to chloramphenicol, ampicillin and benzyl penicillin. [source] Role of the Slt2 mitogen-activated protein kinase pathway in cell wall integrity and virulence in Candida glabrataFEMS YEAST RESEARCH, Issue 3 2010Taiga Miyazaki Abstract The Slt2 mitogen-activated protein kinase pathway plays a major role in maintaining fungal cell wall integrity. In this study, we investigated the effects of SLT2 deletion and overexpression on drug susceptibility and virulence in the opportunistic fungal pathogen Candida glabrata. While the ,slt2 strain showed decreased tolerance to elevated temperature and cell wall-damaging agents, the SLT2 -overexpressing strain exhibited increased tolerance to these stresses. A mutant lacking Rlm1, a transcription factor downstream of Slt2, displayed a cell wall-associated phenotype intermediate to that of the ,slt2 strain. When RLM1 was overexpressed, micafungin tolerance was increased in the wild-type strain and partial restoration of the drug tolerance was observed in the ,slt2 background. It was also demonstrated that echinocandin-class antifungals were more effective against C. glabrata under acidic conditions or when used concurrently with the chitin synthesis inhibitor nikkomycin Z. Finally, in a mouse model of disseminated candidiasis, the deletion and overexpression of C. glabrata SLT2 resulted in mild decreases and increases, respectively, in the CFUs from murine organs compared with the wild-type strain. These fundamental data will help in further understanding the mechanisms of cell wall stress response in C. glabrata and developing more effective treatments using echinocandin antifungals in clinical settings. [source] A new strategy for studying In Vitro the drug susceptibility of clinical isolates of human hepatitis B virusHEPATOLOGY, Issue 4 2004David Durantel Resistance of hepatitis B virus (HBV) to antivirals has become a major clinical problem. Our objective was to develop a new method for the cloning of naturally occurring HBV genomes and a phenotypic assay capable of assessing HBV drug susceptibility and DNA synthesis capacity in vitro. Viral DNA was extracted from sera and was amplified by polymerase chain reaction, and amplicons were cloned into vectors that enable, after cell transfection, the initiation of the intracellular HBV replication cycle. Single or multiple clones were used to transfect Huh7 cells. The viral DNA synthesis capacity and drug susceptibility were determined by measuring the level of intracellular DNA intermediate, synthesized in absence or presence of antiviral, using Southern blot analysis. We have developed, calibrated, then used this phenotypic assay to determine the drug susceptibility of HBV quasispecies isolated throughout the course of therapy from patients selected according to their mutation profile. A multiclonal and longitudinal analysis enabled us to measure the variation of drug susceptibility of different viral quasispecies by comparison of IC50/IC90s with standards. The presence of famciclovir- or lamivudine-induced mutations in the viral population caused a change in viral DNA synthesis capacity and drug susceptibility in vitro, demonstrating the clinical relevance of the assay. In conclusion, our phenotypic assay enables the in vitro characterization of DNA synthesis capacity and drug susceptibility of HBV quasispecies isolated from patients. This assay should allow a better monitoring of patients undergoing antiviral therapy, as well as the screening of novel drugs on emerging resistant strains. (Hepatology 2004;40:855,864). [source] A comparison of HIV-1 drug susceptibility as provided by conventional phenotyping and by a phenotype prediction tool based on viral genotypeJOURNAL OF MEDICAL VIROLOGY, Issue 10 2009Margriet Van Houtte Abstract Concordance between the conventional HIV-1 phenotypic drug resistance assay, PhenoSenseÔ (PS), and virco®TYPE HIV-1 (vT), a drug resistance assay based on prediction of the phenotype, was investigated in a data set from the Stanford HIV Resistance database (hivdb). Depending on the drug, between 287 and 902 genotype,phenotype data pairs were available for comparisons. Test results (fold-change values) in the two assays were highly correlated, with an overall mean correlation coefficient of 0.90 using single PS measurements. This coefficient rose to 0.94 when the vT results were compared to the mean of repeat PS measurements. These results are comparable with the corresponding correlation coefficients of 0.87 and 0.95, calculated using single measurements, and the mean of repeat measurements, respectively, as obtained in the Antivirogram® assay, the conventional HIV-1 phenotypic drug resistance test on which vT is based. The proportion of resistance calls resulting in a "major" discordance (fully susceptible or maximal response by one assay but fully resistant or minimal response by the other) ranged from 0% to 8.1% for drugs for which two clinical test cut-offs were available in both assays (didanosine, abacavir, tenofovir, saquinavir/r, fosamprenavir/r, and lopinavir/r), from 2.4% to 8.1% for the drugs for which two clinical test cut-offs were available in the vT assay and one clinical test cut-off in the PS assay (lamivudine, stavudine, indinavir/r, and atazanavir/r) and from 3.1% to 10.3% for drugs for which biological test cut-offs were used (zidovudine, nevirapine, delavirdine, efavirenz, indinavir, ritonavir, nelfinavir, saquinavir, and fosamprenavir). Our analyses suggest that these assays provide comparable resistance information, which will be of value to physicians who may be presented with either or both types of test report in their practice. J. Med. Virol. 81:1702,1709, 2009. © 2009 Wiley-Liss, Inc. [source] A new strategy based on recombinant viruses as a tool for assessing drug susceptibility of human immunodeficiency virus type 1JOURNAL OF MEDICAL VIROLOGY, Issue 2 2007J. Garcia-Perez Abstract The emergence of drug-resistant variants during antiretroviral therapy is a serious obstacle to sustained suppression of the human immunodeficiency virus type 1 (HIV-1). For that reason, resistance assays are essential to guide clinicians in the selection of optimal treatment regimens. Genotypic assays are less expensive and results are available faster than phenotypic assays. However, in heavily experienced patients with multiple treatment failures interpretation of complex mutation patterns remains difficult, and in these cases phenotypic assays are recommended. This report describes a novel recombinant virus assay where protease (PR) and reverse transcriptase (RT) sequences derived from the plasma isolated from patients are introduced into the back-bone of an HIV molecular clone that expresses Renilla luciferase protein in the place of nef gene. All drug resistance profiles analyzed correlate with previously reported data and showed high reproducibility. This assay, in addition to a fast (completed in 10 days), precise, reproducible and automated method, presents several advantages as compared to other phenotypic assays. The system described below allows the generation of recombinant viruses with multiples cycles of replication carrying a reporter gene in their genomes. These features increase the sensitivity of the test, an important aspect to be considered in the evaluation of less fit viral isolates. In conclusion, the assay permits the quantitation of the level of resistance of clinical HIV-1 isolates to PR and RT inhibitors. J. Med. Virol. 79:127,137, 2007. © 2006 Wiley-Liss, Inc. [source] | |||||||||||||