Multisite Evaluation of Phenotypic Mycobacterium tuberculosis Drug Susceptibility Testing Methods Público
Whitesell, Amy (Spring 2018)
Abstract
Drug susceptibility testing (DST) of Mycobacterium tuberculosis (MTB) is crucial in rapidly detecting and eliminating drug resistance. However, phenotypic DST methods have proven difficult to standardize, and previous studies have shown that discordant DST results may occur between and within laboratories based on multiple factors including method, drug, concentration, and genetic mutation(s) present in the isolate. To further investigate this discordance, an expanded Model Performance Evaluation Program (MPEP) study was conducted by the Centers for Disease Control and Prevention (CDC) Division of Tuberculosis Elimination, Laboratory Branch and the Association of Public Health Laboratories (APHL). Thirty MTB isolates previously characterized by CDC DST methods were available, including 8 sets of duplicates. These were sent to a total of 12 public health and clinical laboratories where phenotypic DST was performed by three different methods: indirect agar proportion method, BACTEC™ mycobacterial growth indicator tubes (MGIT) 960™, and Sensititre™ Mycobacterium tuberculosis MIC plate. Molecular detection of drug resistance (MDDR) was also performed by sequencing target loci to detect mutations associated with drug resistance. Site-specific agreement with a growth-based, expected result as well as agreement with a composite result incorporating resistance-conferring mutations was assessed. A Fleiss kappa estimate was calculated in order to measure interlaboratory agreement independent of previous characterization. Agreement was found to vary by site, method, drug, and concentration. Interlaboratory agreement and agreement to the expected, growth-based result was highest for amikacin and kanamycin (range: 0.90 [95% CI: 0.71, 1.00], 1.00 [95% CI: 1.00, 1.00]) and lowest for ethambutol and para-aminosalicylic acid. Agreement with the composite result was worse for rifampin and rifabutin compared to agreement with the expected results, and improved for capreomycin. Many findings were consistent with previously described patterns of discordance, and further supported evidence that discordant results can be observed across multiple methods, drugs, and strains.
Table of Contents
Chapter I: Background ………………………………………………… 1
Chapter II: Manuscript
Introduction ……………………………………………………………… 19
Materials and Methods …………………………………………………. 21
Results …………………………………………………………………………… 28
Discussion ……………………………………………………………… 39
References ……………………………………………………………… 54
Tables …………………………………………………………………………… 65-71
Figures & Figure Legends ……………………………………… 72-80
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