Publications by authors named "Sophia B Georghiou"

18 Publications

  • Page 1 of 1

Analytical performance of the Xpert MTB/XDR® assay for tuberculosis and expanded resistance detection.

Diagn Microbiol Infect Dis 2021 Sep 20;101(1):115397. Epub 2021 Apr 20.

FIND, Geneva, Switzerland; Division of Tropical Medicine, Center of Infectious Diseases, University Hospital of Heidelberg, Heidelberg, Germany.

In a manufacturer-independent laboratory validation study, the Xpert MTB/XDR® assay demonstrated equivalent limit of detection to Xpert MTB/RIF®, detected 100% of tested resistance mutations and showed some utility for resistance detection in strain mixtures. The Xpert MTB/XDR assay is a reliable, sensitive assay for tuberculosis and expanded resistance detection.
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http://dx.doi.org/10.1016/j.diagmicrobio.2021.115397DOI Listing
September 2021

On the Consequences of Poorly Defined Breakpoints for Rifampin Susceptibility Testing of Mycobacterium tuberculosis Complex.

J Clin Microbiol 2021 03 19;59(4). Epub 2021 Mar 19.

University of South Florida College of Public Health and Morsani College of Medicine, Tampa, Florida, USA

In a recent report of a systematic review of critical concentrations (CCs), the World Health Organization (WHO) lowered the rifampin (RIF) CC for antimicrobial susceptibility testing (AST) of the complex using Middlebrook 7H10 medium and the Bactec Mycobacterial Growth Indicator Tube (MGIT) 960 system from 1 to 0.5 μg/ml. The previous RIF CC for 7H10 had been in use for over half a century. Because it had served as the reference standard, it contributed to the endorsement of inappropriately high CCs for other AST methods, including the U.S. Food and Drug Administration (FDA)-approved MGIT system. Moreover, this resulted in confusion about the interpretation of seven borderline resistance mutations in (i.e., L430P, D435Y, H445L, H445N, H445S, L452P, and I491F). In this issue of the , Shea et al. (J Clin Microbiol 59:e01885-20, 2021, https://doi.org/10.1128/JCM.01885-20) provide evidence that the CC endorsed by the Clinical and Laboratory Standards Institute for the Sensititre MYCOTB system, which is not FDA approved but is CE-IVD marked in the European Union, is likely also too high. These findings underscore the importance of calibrating AST methods against a rigorously defined reference standard, as recently proposed by the European Committee on Antimicrobial Susceptibility Testing, as well as the value of routine next-generation sequencing for investigating discordant AST results.
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http://dx.doi.org/10.1128/JCM.02328-20DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8092724PMC
March 2021

Laboratory Evaluation of a Lateral-Flow Cell for Molecular Detection of First-Line and Second-Line Antituberculosis Drug Resistance.

J Clin Microbiol 2020 10 21;58(11). Epub 2020 Oct 21.

Department of Medicine, University of California, San Diego, La Jolla, California, USA.

Despite the WHO's call for universal drug susceptibility testing for all patients being evaluated for tuberculosis (TB), a lack of rapid diagnostic tests which can fully describe TB resistance patterns is a major challenge in ensuring that all persons diagnosed with drug-resistant TB are started on an appropriate treatment regime. We evaluated the accuracy of the Akonni Biosystems XDR-TB TruArray and lateral-flow cell (XDR-LFC), a novel multiplex assay to simultaneously detect mutations across seven genes that confer resistance to both first- and second-line anti-TB drugs. The XDR-LFC includes 271 discrete three-dimensional gel elements with target-specific probes for identifying mutations in , promoter, and promoter (isoniazid), (rifampin), (fluoroquinolones), and promoter (kanamycin), and (capreomycin and amikacin). We evaluated XDR-LFC performance with 87 phenotypically and genotypically characterized clinical isolates. The overall assay levels of accuracy for mutation detection in specific genes were 98.6% for promoter and 100.0% for the genes , promoter, promoter, , , and The sensitivity and specificity against phenotypic reference were 100% and 100% for isoniazid, 98.4% and 50% for rifampin (specificity increased to 100% once the strains with documented low-level resistance mutations in were excluded), 96.2% and 100% for fluoroquinolones, 92.6% and 100% for kanamycin, 93.9% and 97.4% for capreomycin, and 80% and 100% for amikacin. The XDR-LFC solution appears to be a promising new tool for accurate detection of resistance to both first- and second-line anti-TB drugs.
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http://dx.doi.org/10.1128/JCM.01417-20DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7587100PMC
October 2020

Guidance for Studies Evaluating the Accuracy of Rapid Tuberculosis Drug-Susceptibility Tests.

J Infect Dis 2019 10;220(220 Suppl 3):S126-S135

FIND, Geneva, Switzerland.

The development and implementation of rapid molecular diagnostics for tuberculosis (TB) drug-susceptibility testing is critical to inform treatment of patients and to prevent the emergence and spread of resistance. Optimal trial planning for existing tests and those in development will be critical to rapidly gather the evidence necessary to inform World Health Organization review and to support potential policy recommendations. The evidence necessary includes an assessment of the performance for TB and resistance detection as well as an assessment of the operational characteristics of these platforms. The performance assessment should include analytical studies to confirm the limit of detection and assay ability to detect mutations conferring resistance across globally representative strains. The analytical evaluation is typically followed by multisite clinical evaluation studies to confirm diagnostic performance in sites and populations of intended use. This paper summarizes the considerations for the design of these analytical and clinical studies.
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http://dx.doi.org/10.1093/infdis/jiz106DOI Listing
October 2019

Impact of Fluoroquinolone Use on Mortality Among a Cohort of Patients With Suspected Drug-Resistant Tuberculosis.

Clin Infect Dis 2017 Sep;65(5):772-778

Department of Medicine, University of California, San Diego, La Jolla.

Background: Previous retrospective and in vitro studies suggest that use of later-generation fluoroquinolones may reduce mortality risk and improve treatment outcomes for drug-resistant tuberculosis (TB) patients, including individuals resistant to a fluoroquinolone. Meta-analysis results are mixed and few studies have examined this relationship prospectively.

Methods: As part of a comparative diagnostic study, we conducted a prospective cohort study with 834 Mycobacterium tuberculosis-infected patients from selected hospitals and clinics with high prevalence of drug-resistant TB in India, Moldova, and South Africa. We used Cox proportional hazards regression models to assess the association between later-generation fluoroquinolone (moxifloxacin or levofloxacin) use and patient mortality, adjusting for risk factors typically associated with poor treatment outcomes.

Results: After adjusting for phenotypic resistance profile, low body mass index (<18.5 kg/m2), human immunodeficiency virus status, and study site, participants treated with a later-generation fluoroquinolone had half the risk of mortality compared with participants either not treated with any fluoroquinolone or treated only with an earlier-generation fluoroquinolone (adjusted hazard ratio, 0.46 [95% confidence interval, .26-.80]) during follow-up.

Conclusions: Use of later-generation fluoroquinolones significantly reduced patient mortality risk in our cohort, suggesting that removal of a later-generation fluoroquinolone from a treatment regimen because of demonstrated resistance to an earlier-generation fluoroquinolone might increase mortality risk. Further studies should evaluate the effectiveness of later-generation fluoroquinolones among patients with and without resistance to early-generation fluoroquinolones.

Clinical Trials Registration: NCT02170441.
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http://dx.doi.org/10.1093/cid/cix422DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5848235PMC
September 2017

Increased Tuberculosis Patient Mortality Associated with Mycobacterium tuberculosis Mutations Conferring Resistance to Second-Line Antituberculous Drugs.

J Clin Microbiol 2017 06 12;55(6):1928-1937. Epub 2017 Apr 12.

Department of Medicine, University of California, San Diego, La Jolla, California, USA.

Rapid molecular diagnostics have great potential to limit the spread of multidrug-resistant tuberculosis (MDR-TB) and extensively drug-resistant tuberculosis (XDR-TB) (M/XDR-TB). These technologies detect mutations in the genome that confer phenotypic drug resistance. However, there have been few data published regarding the relationships between the detected resistance mutations and M/XDR-TB treatment outcomes, limiting our current ability to exploit the full potential of molecular diagnostics. We analyzed clinical, microbiological, and sequencing data for 451 patients and their clinical isolates collected in a multinational, observational cohort study to determine if there was an association between resistance mutations and patient mortality. The presence of an 1401G mutation was associated with significantly higher odds of patient mortality (adjusted odds ratio [OR] = 5.72; 95% confidence interval [CI], 1.65 to 19.84]) after adjusting for relevant patient clinical characteristics and all other resistance mutations. Further analysis of mutations, categorized by the associated resistance level, indicated that the detection of mutations associated with high-level fluoroquinolone (OR, 3.99 [95% CI, 1.10 to 14.40]) and kanamycin (OR, 5.47 [95% CI, 1.64 to 18.24]) resistance was also significantly associated with higher odds of patient mortality, even after accounting for clinical site, patient age, reported smoking history, body mass index (BMI), diabetes, HIV, and all other resistance mutations. Specific and resistance mutations, associated with high-level resistance, were associated with patient mortality as identified in clinical isolates from a diverse M/XDR-TB patient population at three high-burden clinical sites. These results have important implications for the interpretation of molecular diagnostics, including identifying patients at increased risk for mortality during treatment. (This study has been registered at ClinicalTrials.gov under registration no. NCT02170441.).
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http://dx.doi.org/10.1128/JCM.00152-17DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5442550PMC
June 2017

Comparative accuracy of the REBA MTB MDR and Hain MTBDRplus line probe assays for the detection of multidrug-resistant tuberculosis: A multicenter, non-inferiority study.

PLoS One 2017 24;12(3):e0173804. Epub 2017 Mar 24.

Foundation for Innovative New Diagnostics, Geneva, Switzerland.

Introduction: Despite recent diagnostic advances, the majority of multidrug-resistant tuberculosis (MDR-TB) cases remain undiagnosed. Line probes assays (LiPAs) hold great promise to curb the spread of MDR-TB as they can rapidly detect MDR-TB even when laboratory infrastructure is limited, yet few of these assays are currently widely available or supported by World Health Organization (WHO) policy.

Methods: The aim of this prospective, blinded, non-inferiority study was to compare the performance of YD Diagnostics REBA MTB MDR LiPA (YD) to the WHO-endorsed Hain MTBDRplus V1 LiPA (Hain V1) for the detection of rifampicin and isoniazid resistance. In phase 1, YD and Hain V1 diagnostic performance was assessed with selected culture isolates and results were compared to phenotypic drug susceptibility testing (DST) results and targeted sequencing data. In phase 2, both assays were tested on processed sputum samples and results were compared to phenotypic DST results.

Results: In phase 1, YD did not achieve non-inferiority to Hain V1. For isoniazid resistance detection, Hain V1 had a sensitivity of 89% (95%CI 83.8-93%) and specificity of 99.4% (95%CI 96.9-100%). While YD had a similar sensitivity of 92% (95%CI 87.3-95.4%), the specificity was inferior at 92.6% (95%CI 87.6-96%). For rifampicin resistance detection, Hain V1 had a sensitivity of 90.2% (95%CI 84.8-94.2%) and specificity of 98.5% (95%CI 95.7-99.7%) while YD had an inferior sensitivity of 72.4% (95%CI 65.1-78.9%) and a comparable specificity of 98% (95%CI 95-99.5%). Similar results were observed in phase 2. For MDR-TB detection, the sensitivity and specificity of Hain V1 was 93.4% (95%CI 88.2-96.2%) and 96.2% (95%CI 88.2-96.8%), respectively, compared to 75.7% (95%CI 68-82.2%) and 92% (95%CI 88.2-94.9%) for YD.

Conclusions: YD did not achieve non-inferiority with Hain V1. Further improvements and repeat evaluation of YD is necessary prior to recommending its use for clinical settings.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0173804PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5365104PMC
August 2017

Shedding light on the performance of a pyrosequencing assay for drug-resistant tuberculosis diagnosis.

BMC Infect Dis 2016 08 31;16:458. Epub 2016 Aug 31.

Department of Medicine, University of California San Diego, La Jolla, CA, USA.

Background: Rapid molecular diagnostics, with their ability to quickly identify genetic mutations associated with drug resistance in Mycobacterium tuberculosis clinical specimens, have great potential as tools to control multi- and extensively drug-resistant tuberculosis (M/XDR-TB). The Qiagen PyroMark Q96 ID system is a commercially available pyrosequencing (PSQ) platform that has been validated for rapid M/XDR-TB diagnosis. However, the details of the assay's diagnostic and technical performance have yet to be thoroughly investigated in diverse clinical environments.

Methods: This study evaluates the diagnostic performance of the PSQ assay for 1128 clinical specimens from patients from three areas of high TB burden. We report on the diagnostic performance of the PSQ assay between the three sites and identify variables associated with poor PSQ technical performance.

Results: In India, the sensitivity of the PSQ assay ranged from 89 to 98 % for the detection of phenotypic resistance to isoniazid, rifampicin, fluoroquinolones, and the injectables. In Moldova, assay sensitivity ranged from 7 to 94 %, and in South Africa, assay sensitivity ranged from 71 to 92 %. Specificity was high (94-100 %) across all sites. The addition of eis promoter sequencing information greatly improved the sensitivity of kanamycin resistance detection in Moldova (7 % to 79 %). Nearly all (89.4 %) sequencing reactions conducted on smear-positive, culture-positive specimens and most (70.8 %) reactions conducted on smear-negative, culture-positive specimens yielded valid PSQ reads. An investigation into the variables influencing sequencing failures indicated smear negativity, culture negativity, site (Moldova), and sequencing of the rpoB, gyrA, and rrs genes were highly associated with poor PSQ technical performance (adj. OR > 2.0).

Conclusions: This study has important implications for the global implementation of PSQ as a molecular TB diagnostic, as it demonstrates how regional factors may impact PSQ diagnostic performance, while underscoring potential gene targets for optimization to improve overall PSQ assay technical performance.

Trial Registration: ClinicalTrials.gov ( #NCT02170441 ). Registered 12 June 2014.
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http://dx.doi.org/10.1186/s12879-016-1781-yDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5006534PMC
August 2016

Rapid Drug Susceptibility Testing of Drug-Resistant Mycobacterium tuberculosis Isolates Directly from Clinical Samples by Use of Amplicon Sequencing: a Proof-of-Concept Study.

J Clin Microbiol 2016 08 25;54(8):2058-67. Epub 2016 May 25.

Pathogen Genomics, Translational Genomics Research Institute, Flagstaff, Arizona, USA.

Increasingly complex drug-resistant tuberculosis (DR-TB) is a major global health concern and one of the primary reasons why TB is now the leading infectious cause of death worldwide. Rapid characterization of a DR-TB patient's complete drug resistance profile would facilitate individualized treatment in place of empirical treatment, improve treatment outcomes, prevent amplification of resistance, and reduce the transmission of DR-TB. The use of targeted next-generation sequencing (NGS) to obtain drug resistance profiles directly from patient sputum samples has the potential to enable comprehensive evidence-based treatment plans to be implemented quickly, rather than in weeks to months, which is currently needed for phenotypic drug susceptibility testing (DST) results. In this pilot study, we evaluated the performance of amplicon sequencing of Mycobacterium tuberculosis DNA from patient sputum samples using a tabletop NGS technology and automated data analysis to provide a rapid DST solution (the Next Gen-RDST assay). One hundred sixty-six out of 176 (94.3%) sputum samples from the Republic of Moldova yielded complete Next Gen-RDST assay profiles for 7 drugs of interest. We found a high level of concordance of our Next Gen-RDST assay results with phenotypic DST (97.0%) and pyrosequencing (97.8%) results from the same clinical samples. Our Next Gen-RDST assay was also able to estimate the proportion of resistant-to-wild-type alleles down to mixtures of ≤1%, which demonstrates the ability to detect very low levels of resistant variants not detected by pyrosequencing and possibly below the threshold for phenotypic growth methods. The assay as described here could be used as a clinical or surveillance tool.
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http://dx.doi.org/10.1128/JCM.00535-16DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4963505PMC
August 2016

Correlating rrs and eis promoter mutations in clinical isolates of Mycobacterium tuberculosis with phenotypic susceptibility levels to the second-line injectables.

Int J Mycobacteriol 2016 Mar 1;5(1):1-6. Epub 2015 Oct 1.

Microbiology Section, Department of Laboratory Medicine, P. D. Hinduja Hospital & Medical Research Centre, Mumbai, India. Electronic address:

Objective/background: The in vitro drug-susceptibility testing of Mycobacterium tuberculosis reports isolates as resistant or susceptible on the basis of single critical concentrations. It is evident that drug resistance in M. tuberculosis is quite heterogeneous, and involves low level, moderate level, and high level of drug-resistant phenotypes. Thus, the aim of our study was to correlate rrs (X52917) and eis (AF144099) promoter mutations, found in M. tuberculosis isolates, with corresponding minimum inhibitory concentrations of amikacin, kanamycin, and capreomycin.

Methods: Ninety M. tuberculosis clinical isolates were analyzed in this study. The minimum inhibitory concentrations were determined by MGIT 960 for 59 isolates with resistance-associated mutations in the rrs and eis promoter gene regions, and 31 isolates with wild-type sequences, as determined by the GenoType MTBDRsl (version 1) assay.

Results: The rrs A1401G mutation was identified in 48 isolates resistant to the second-line injectables. The eis promoter mutations C-14T (n=3), G-10C (n=3), G-10A (n=3), and C-12T (n=2) were found within 11 isolates with various resistance profiles to the second-line injectables. Thirty-one isolates had wild-type sequences for the rrs and eis promoter gene regions of interest, one of which was amikacin, kanamycin, and capreomycin resistant. The isolates with the rrs A1401G mutation had amikacin, kanamycin, and capreomycin minimum inhibitory concentrations of >40mg/L, >20mg/L, and 5-15mg/L, respectively. The isolates with eis promoter mutations had amikacin, kanamycin, and capreomycin minimum inhibitory concentrations of 0.25-1.0mg/L, 0.625-10mg/L, and 0.625-2.5mg/L, respectively.

Conclusion: This study provides a preliminary basis for the prediction of phenotypic-resistance levels to the second-line injectables based upon the presence of genetic mutations associated with amikacin, kanamycin, and capreomycin resistance. The results suggest that isolates with eis promoter mutations have consistently lower resistance levels to amikacin, kanamycin, and capreomycin than isolates with the rrs A1401G mutation.
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http://dx.doi.org/10.1016/j.ijmyco.2015.09.001DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4863938PMC
March 2016

MTBDRplus and MTBDRsl Assays: Absence of Wild-Type Probe Hybridization and Implications for Detection of Drug-Resistant Tuberculosis.

J Clin Microbiol 2016 Apr 13;54(4):912-8. Epub 2016 Jan 13.

University of California, San Diego, California, USA.

Accurate identification of drug-resistantMycobacterium tuberculosisis imperative for effective treatment and subsequent reduction in disease transmission. Line probe assays rapidly detect mutations associated with resistance and wild-type sequences associated with susceptibility. Examination of molecular-level performance is necessary for improved assay result interpretation and for continued diagnostic development. Using data collected from a large, multisite diagnostic study, probe hybridization results from line probe assays, MTBDRplusand MTBDRsl, were compared to those of sequencing, and the diagnostic performance of each individual mutation and wild-type probe was assessed. Line probe assay results classified as resistant due to the absence of wild-type probe hybridization were compared to those of sequencing to determine if novel mutations were inhibiting wild-type probe hybridization. The contribution of absent wild-type probe hybridization to the detection of drug resistance was assessed via comparison to a phenotypic reference standard. In our study, mutation probes demonstrated significantly higher specificities than wild-type probes and wild-type probes demonstrated marginally higher sensitivities than mutation probes, an ideal combination for detecting the presence of resistance conferring mutations while yielding the fewest number of false-positive results. The absence of wild-type probe hybridization without mutation probe hybridization was determined to be primarily the result of failure of mutation probe hybridization and not the result of novel or rare mutations. Compared to phenotypic culture-based drug susceptibility testing, the absence of wild-type probe hybridization without mutation probe hybridization significantly contributed to the detection of phenotypic rifampin and fluoroquinolone resistance with negligible increases in false-positive results.
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http://dx.doi.org/10.1128/JCM.02505-15DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4809938PMC
April 2016

Performance Comparison of Three Rapid Tests for the Diagnosis of Drug-Resistant Tuberculosis.

PLoS One 2015 31;10(8):e0136861. Epub 2015 Aug 31.

University of Arkansas, Little Rock, Arkansas, United States of America.

Background: The aim of this study was to compare the performance of several recently developed assays for the detection of multi- and extensively drug-resistant tuberculosis (M/XDR-TB) in a large, multinational field trial.

Methods: Samples from 1,128 M/XDR-TB suspects were examined by Line Probe Assay (LPA), Pyrosequencing (PSQ), and Microscopic Observation of Drug Susceptibility (MODS) and compared to the BACTEC MGIT960 reference standard to detect M/XDR-TB directly from patient sputum samples collected at TB clinics in India, Moldova, and South Africa.

Results: Specificity for all three assays was excellent: 97-100% for isoniazid (INH), rifampin (RIF), moxifloxacin (MOX) and ofloxacin (OFX) and 99-100% for amikacin (AMK), capreomycin (CAP) and kanamycin (KAN) resistance. Sensitivities were lower, but still very good: 94-100% for INH, RIF, MOX and OFX, and 84-90% for AMK and CAP, but only 48-62% for KAN. In terms of agreement, statistically significant differences were only found for detection of RIF (MODS outperformed PSQ) and KAN (MODS outperformed LPA and PSQ) resistance. Mean time-to-result was 1.1 days for LPA and PSQ, 14.3 days for MODS, and 24.7 days for MGIT.

Conclusions: All three rapid assays evaluated provide clinicians with timely detection of resistance to the drugs tested; with molecular results available one day following laboratory receipt of samples. In particular, the very high specificity seen for detection of drug resistance means that clinicians can use the results of these rapid tests to avoid the use of toxic drugs to which the infecting organism is resistant and develop treatment regiments that have a higher likelihood of yielding a successful outcome.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0136861PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4556461PMC
May 2016

Defining multidrug-resistant tuberculosis: correlating GenoType MTBDRplus assay results with minimum inhibitory concentrations.

Diagn Microbiol Infect Dis 2015 May 29;82(1):49-53. Epub 2015 Jan 29.

Microbiology Section, Department of Laboratory Medicine, P.D. Hinduja National Hospital and Medical Research Center, Mumbai, India. Electronic address:

This study correlates MICs of rifampicin (RIF) and isoniazid (INH) with GenoType MTBDRplus assay results for drug-resistant Mycobacterium tuberculosis (MTB) clinical isolates. MICs of RIF and INH were established for 84 and 90 isolates, respectively, testing 7 concentrations of each drug. Genotypic resistance to each drug was determined by GenoType MTBDRplus assay with 50 representative mutations confirmed by pyrosequencing, with mutations in the rpoB gene associated with RIF resistance and mutations in the katG and/or inhA genes associated with INH resistance. Based upon the correlation of MICs with specific genetic profiles, relative resistance levels were established for each isolate. Results indicate that MTB phenotypic resistance, currently based upon the testing of isolate susceptibility to a single drug concentration, may be more accurately profiled via quantitative MICs, and therefore, the correlation of molecular diagnostic results with specific MICs may allow for more optimal treatment of infections.
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http://dx.doi.org/10.1016/j.diagmicrobio.2015.01.009DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4414878PMC
May 2015

Evaluation of genetic mutations associated with Mycobacterium tuberculosis resistance to amikacin, kanamycin and capreomycin: a systematic review.

PLoS One 2012 29;7(3):e33275. Epub 2012 Mar 29.

Department of Molecular Biology, The Scripps Research Institute, La Jolla, California, United States of America.

Background: Rapid molecular diagnostics for detecting multidrug-resistant and extensively drug-resistant tuberculosis (M/XDR-TB) primarily identify mutations in Mycobacterium tuberculosis (Mtb) genes associated with drug resistance. Their accuracy, however, is dependent largely on the strength of the association between a specific mutation and the phenotypic resistance of the isolate with that mutation, which is not always 100%. While this relationship is well established and reliable for first-line anti-TB drugs, rifampin and isoniazid, it is less well-studied and understood for second-line, injectable drugs, amikacin (AMK), kanamycin (KAN) and capreomycin (CAP).

Methodology/principal Findings: We conducted a systematic review of all published studies evaluating Mtb mutations associated with resistance to AMK, KAN, CAP in order to characterize the diversity and frequency of mutations as well as describe the strength of the association between specific mutations and phenotypic resistance in global populations. Our objective was to determine the potential utility and reliability of these mutations as diagnostic markers for detecting AMK, KAN and CAP resistance. Mutation data was reviewed for 1,585 unique clinical isolates from four continents and over 18 countries. Mutations in the rrs, tlyA, eis promoter and gidB genes were associated with AMK, KAN and/or CAP resistance.

Conclusions/significance: The rrs A1401G mutation was present in the majority of AMK, KAN and CAP resistant Mtb strains reviewed, but was also found in 7% of CAP susceptible strains. The 1401 mutation alone, however, was not found with sufficient frequency to detect more than 70-80% of global Mtb strains resistant to AMK and CAP, and 60% of strains resistant to KAN. Additional mutations in the rrs, eis promoter, tlyA and gidB genes appear to be associated with resistance and could improve sensitivity and specificity of future diagnostics.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0033275PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3315572PMC
August 2012

Bacillus thuringiensis Cry5B protein is highly efficacious as a single-dose therapy against an intestinal roundworm infection in mice.

PLoS Negl Trop Dis 2010 Mar 2;4(3):e614. Epub 2010 Mar 2.

Section of Cell and Developmental Biology, University of California, San Diego, La Jolla, California, United States of America.

Background: Intestinal parasitic nematode diseases are one of the great diseases of our time. Intestinal roundworm parasites, including hookworms, whipworms, and Ascaris, infect well over 1 billion people and cause significant morbidity, especially in children and pregnant women. To date, there is only one drug, albendazole, with adequate efficacy against these parasites to be used in mass drug administration, although tribendimidine may emerge as a second. Given the hundreds of millions of people to be treated, the threat of parasite resistance, and the inadequacy of current treatments, new anthelmintics are urgently needed. Bacillus thuringiensis (Bt) crystal (Cry) proteins are the most common used biologically produced insecticides in the world and are considered non-toxic to vertebrates.

Methods/principal Findings: Here we study the ability of a nematicidal Cry protein, Cry5B, to effect a cure in mice of a chronic roundworm infection caused by the natural intestinal parasite, Heligmosomoides bakeri (formerly polygyrus). We show that Cry5B produced from either of two Bt strains can act as an anthelmintic in vivo when administered as a single dose, achieving a approximately 98% reduction in parasite egg production and approximately 70% reduction in worm burdens when delivered per os at approximately 700 nmoles/kg (90-100 mg/kg). Furthermore, our data, combined with the findings of others, suggest that the relative efficacy of Cry5B is either comparable or superior to current anthelmintics. We also demonstrate that Cry5B is likely to be degraded quite rapidly in the stomach, suggesting that the actual dose reaching the parasites is very small.

Conclusions/significance: This study indicates that Bt Cry proteins such as Cry5B have excellent anthelmintic properties in vivo and that proper formulation of the protein is likely to reveal a superior anthelmintic.
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http://dx.doi.org/10.1371/journal.pntd.0000614DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2830470PMC
March 2010
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