scholarly journals Interpretation of Discordant Rifampicin Susceptibility Test Results Obtained Using GeneXpert vs Phenotypic Drug Susceptibility Testing

2020 ◽  
Vol 7 (8) ◽  
Author(s):  
Fengmin Huo ◽  
Yifeng Ma ◽  
Rongmei Liu ◽  
Liping Ma ◽  
Shanshan Li ◽  
...  
Keyword(s):  
Dna Sequences ◽  
Susceptibility Testing ◽  
Bacterial Load ◽  
Rpob Gene ◽  
Drug Susceptibility ◽  
Drug Susceptibility Testing ◽  
Susceptibility Test ◽  
Patient Treatment ◽  
Common Mutation ◽  
Test Results

Abstract Background The 3-month difference in turnaround time between Xpert and conventional phenotypic drug susceptibility testing (pDST) causes patient treatment challenges when pDST rifampin (RIF) susceptibility results and earlier Xpert results disagree, resulting in unnecessary tuberculosis (TB) patient exposure to toxic second-line drugs. Here, the prevalence of discordant RIF susceptibility test results, specifically Xpert (resistant) vs pDST (susceptible) results, was determined. Methods Tuberculosis patients enrolled between January 2015 and June 2018 at Beijing Chest Hospital who consecutively tested positive for RIF resistance using Xpert then negative using pDST were studied. DNA sequences and minimal inhibitory concentration (MIC) results provided insights for understanding discordant results. Results Of 26 826 patients with suggestive TB symptoms undergoing Xpert MTB/RIF testing, 728 diagnosed as RIF-resistant were evaluated. Of these, 118 (16.2%) exhibiting Xpert RIF resistance and phenotypic RIF susceptibility yielded 104 successfully subcultured isolates; of these, 86 (82.7%) harbored rpoB gene RIF resistance–determining region mutations and 18 (17.3%) did not. The Leu511Pro (25.0%) and Leu533Pro (17.3%) mutations were most frequently associated with discordant RIF susceptibility test results. Of the 86 isolates with rpoB mutations, 42 (48.8%) with MICs ≤1.0 mg/L were assigned to the RIF-susceptible group, with Leu511Pro being the most common mutation observed. Isolates with a very low bacterial load were most frequently misdiagnosed as RIF-resistant by Xpert. Conclusions Approximately one-sixth of RIF-resistant TB isolates identified via Xpert yielded discordant pDST results due to questionable interpretation of specific “disputed” mutations. Thus, a diagnostic flowchart should be used to correctly interpret Xpert RIF resistance results to best guide patient treatment.

scholarly journals Safety and Therapeutic Efficacy of Thymoquinone-Loaded Liposomes against Drug-Sensitive and Drug-Resistant Acinetobacter baumannii

Pharmaceutics ◽  
2021 ◽  
Vol 13 (5) ◽  
pp. 677
Author(s):  
Khaled S. Allemailem ◽  
Abdullah M. Alnuqaydan ◽  
Ahmad Almatroudi ◽  
Faris Alrumaihi ◽  
Aseel Aljaghwani ◽  
...  
Keyword(s):  
Survival Rate ◽  
Acinetobacter Baumannii ◽  
Therapeutic Efficacy ◽  
Susceptibility Testing ◽  
Bacterial Load ◽  
Drug Susceptibility ◽  
Drug Susceptibility Testing ◽  
Drug Resistant ◽  
Liver And Kidney ◽  
Time Kill

In the present study, we investigated the activity of free thymoquinone (TQ) or liposomal thymoquinone (Lip-TQ) in comparison to standard antibiotic amoxicillin (AMX) against the drug-sensitive and drug-resistant Acinetobacter baumannii. A liposomal formulation of TQ was prepared and characterized and its toxicity was evaluated by analyzing the hematological, liver and kidney function parameters. TQ was effective against both drug-sensitive and drug-resistant A. baumannii as shown by the findings of drug susceptibility testing and time kill kinetics. Moreover, the therapeutic efficacy of TQ or Lip-TQ against A. baumannii was assessed by the survival rate and the bacterial load in the lung tissues of treated mice. The mice infected with drug-sensitive A. baumannii exhibited a 90% survival rate on day 30 post treatment with Lip-TQ at a dose of 10 mg/kg, whereas the mice treated with AMX (10 mg/kg) had a 100% survival rate. On the other hand, the mice infected with drug-resistant A. baumannii had a 70% survival rate in the group treated with Lip-TQ, whereas AMX was ineffective against drug-resistant A. baumannii and all the mice died within day 30 after the treatment. Moreover, Lip-TQ treatment effectively reduced the bacterial load in the lung tissues of the mice infected with the drug-sensitive and drug-resistant A. baumannii. Moreover, the blood of the mice treated with Lip-TQ had reduced levels of inflammation markers, leukocytes and neutrophils. The results of the present study suggest that Lip-TQ may prove to be an effective therapeutic formulation in the treatment of the drug-sensitive or drug-resistant A. baumannii infection as well.

scholarly journals DETERMINATION OF RIFAMPICIN MONO-RESISTANCE MYCOBACTERIUM TUBERCULOSIS IN THE NATIONAL TUBERCULOSIS CONTROL PROGRAMME IN SANA'A CITY-YEMEN: A SIGNIFICANT PHENOMENON IN WAR REGION WITH HIGH PREVALENCE TUBERCLOISIS

2019 ◽  
Author(s):  
Roqiaa Mohammed Ahmed Al-Hrazi ◽  
Hassan A. Al-Shamahy ◽  
Bushra Mohammed Jaadan
Keyword(s):  
Risk Factors ◽  
Dna Sequences ◽  
Susceptibility Testing ◽  
Drug Susceptibility ◽  
Drug Susceptibility Testing ◽  
Control Programme ◽  
Treatment Rate ◽  
Rf Gene ◽  
Significant Rate ◽  
Associated Risk Factors

The current study was undertaken in Sana'a city, Yemen, which has one of the highest rates of Tuberculosis (TB) in the Region. The aims of this retrospective study were determined the prevalence of true RIF's mono-resistance, using the gold standard of molecular assays comparing with culture based phenotypic drug susceptibility testing (DST), and determined the associated risk factors of contracting RF gene among Yemeni TB patients. Patient's data were collected in a predesigned questionnaire which included demographic information and the relevant risk factors associated with RIF. All sputum specimens received were routinely cultured, and, underwent phenotypic drug susceptibility testing. DNA sequences specific for MTB and RIF were detected by automated molecular test. The total end treatment rate was 5.94% of the total cases (11/185). MTB gene was positive for all cases which indicate more sensitive than sputum examination; 3.2% of total patients show RIF's genes positive. Higher rate of RIF with male (5.4%), and low in female patients (1.8%). There was higher rate of RIF with age group 36-45 years (8.7%) and >15 years (7.1%). There was significant rate of RIF gene with after food drug taken (RIF=13.3%, with Odds ratio (OR)=6.4), and with DOTs program (RIF=10%, with OR=6.4). In addition, there was significant rate of RIF gene with one dose regimen (11.8%, OR=5.5). In conclusion, this study reveals the presence of RIF- M. tuberculosis in Sana’a, Yemen and most of them were observed among patients who default treatment. This is considered as a threat to TB control programme and it is recommended that strategies should be put in place in order to ensure patients’ compliance and monitoring of patients’ response to TB treatment.

scholarly journals Molecular and Growth-Based Drug Susceptibility Testing ofMycobacterium tuberculosisComplex for Ethambutol Resistance in the United States

2016 ◽  
Vol 2016 ◽  
pp. 1-5 ◽  
Author(s):  
Mitchell A. Yakrus ◽  
Jeffrey Driscoll ◽  
Allison McAlister ◽  
David Sikes ◽  
Denise Hartline ◽  
...  
Keyword(s):  
Dna Sequencing ◽  
Molecular Detection ◽  
Susceptibility Testing ◽  
The United States ◽  
Drug Susceptibility ◽  
Drug Susceptibility Testing ◽  
Test Results ◽  
Drug Susceptibility Test ◽  
Control And Prevention ◽  
Drug Regimens

Ethambutol (EMB) is used as a part of drug regimens for treatment of tuberculosis (TB). Susceptibility ofMycobacterium tuberculosiscomplex (MTBC) isolates to EMB can be discerned by DNA sequencing to detect mutations in theembBgene associated with resistance. US Public Health Laboratories (PHL) primarily use growth-based drug susceptibility test (DST) methods to determine EMB resistance. The Centers for Disease Control and Prevention (CDC) provides a service for molecular detection of drug resistance (MDDR) by DNA sequencing and concurrent growth-based DST using agar proportion. PHL and CDC test results were compared for 211 MTBC samples submitted to CDC from September 2009 through February 2011. Concordance between growth-based DST results from PHL and CDC was 88.2%. A growth-based comparison of 39 samples, where anembBmutation associated with EMB resistance was detected, revealed a higher percentage of EMB resistance by CDC (84.6%) than by PHL (59.0%) which was significant (Pvalue = 0.002). Discordance between all growth-based test results from PHL and CDC was also significant (Pvalue = 0.003). Most discordance was linked to false susceptibility using the BACTEC™MGIT™960 (MGIT) growth-based system. Our analysis supports coalescing growth-based and molecular results for an informed interpretation of potential EMB resistance.

scholarly journals Characterization of katG, inhA, rpoB and pncA in Mycobacterium tuberculosis isolates from MDR-TB risk patients in Thailand

2020 ◽  
Vol 14 (03) ◽  
pp. 268-276
Author(s):  
Krairerk Suthum ◽  
Worada Samosornsuk ◽  
Seksun Samosornsuk
Keyword(s):  
Mycobacterium Tuberculosis ◽  
Dna Sequencing ◽  
Susceptibility Testing ◽  
Gene Mutations ◽  
Drug Susceptibility ◽  
Multidrug Resistant ◽  
Drug Susceptibility Testing ◽  
Common Mutation ◽  
Mdr Tb ◽  
Risk Patients

Introduction: Multidrug-resistant tuberculosis (MDR-TB) is commonly found in Thailand especially in the public health region 5, the Western region of Thailand. This study’s aim was to characterize katG, inhA, rpoB and pncA genes in Mycobacterium tuberculosis. Methodology: One hundred strains of Mycobacterium tuberculosis (MTB) were isolated from sputum samples of MDR-TB risk patients in the laboratory of the Office of Disease Prevention and Control 5th Ratchaburi province, Thailand from January to December 2015. Drug susceptibility testing (DST) was performed using a BACTEC MGIT 960 system. Furthermore, the genes katG, inhA, rpoB and pncA were characterized by DNA sequencing. Results: Of a total of 100 MTB samples which underwent drug susceptibility testing, 42% showed isoniazid (INH) and rifampicin (RIF) resistance, and a further 25% showed INH mono-resistance (25%). The most common gene mutations found using DNA sequencing were katG_Ser315Thr (70%), rpoB_Ser531leu (81%) and pncA_Ile31Thr (84%). The common mutation of pncA_Ile31Thr substitution was detected in 26 of 91 (29%) pyrazinamide (PZA) susceptible isolates. Conclusion: Using DNA sequencing to screen for gene mutations conferring drug resistance may be feasible and use less time than using DST to detect resistance patterns.

scholarly journals Role of Disputed Mutations in the rpoB Gene in Interpretation of Automated Liquid MGIT Culture Results for Rifampin Susceptibility Testing of Mycobacterium tuberculosis

2018 ◽  
Vol 56 (5) ◽  
Author(s):  
Paolo Miotto ◽  
Andrea M. Cabibbe ◽  
Emanuele Borroni ◽  
Massimo Degano ◽  
Daniela M. Cirillo
Keyword(s):  
Mycobacterium Tuberculosis ◽  
In Silico ◽  
Susceptibility Testing ◽  
Rpob Gene ◽  
Drug Susceptibility ◽  
Drug Susceptibility Testing ◽  
Missense Mutations ◽  
Content Type ◽  
Low Level ◽  
Clinical Resistance

ABSTRACT Low-level rifampin resistance associated with specific rpoB mutations (referred as “disputed”) in Mycobacterium tuberculosis is easily missed by some phenotypic methods. To understand the mechanism by which some mutations are systematically missed by MGIT phenotypic testing, we performed an in silico analysis of their effect on the structural interaction between the RpoB protein and rifampin. We also characterized 24 representative clinical isolates by determining MICs on 7H10 agar and testing them by an extended MGIT protocol. We analyzed 2,097 line probe assays, and 156 (7.4%) cases showed a hybridization pattern referred to here as “no wild type + no mutation.” Isolates harboring “disputed” mutations (L430P, D435Y, H445C/L/N/S, and L452P) tested susceptible in MGIT, with prevalence ranging from 15 to 57% (overall, 16 out of 55 isolates [29%]). Our in silico analysis did not highlight any difference between “disputed” and “undisputed” substitutions, indicating that all rpoB missense mutations affect the rifampin binding site. MIC testing showed that “undisputed” mutations are associated with higher MIC values (≥20 mg/liter) compared to “disputed” mutations (4 to >20 mg/liter). Whereas “undisputed” mutations didn't show any delay (Δ) in time to positivity of the test tube compared to the control tube on extended MGIT protocol, “disputed” mutations showed a mean Δ of 7.2 days (95% confidence interval [CI], 4.2 to 10.2 days; P < 0.05), providing evidence that mutations conferring low-level resistance are associated with a delay in growth on MGIT. Considering the proved relevance of L430P, D435Y, H445C/L/N, and L452P mutations in determining clinical resistance, genotypic drug susceptibility testing (DST) should be used to replace phenotypic results (MGIT) when such mutations are found.

Accuracy of molecular drug susceptibility testing amongst tuberculosis patients in Karakalpakstan, Uzbekistan

2021 ◽  
Author(s):  
Horacio Gil ◽  
Hasmik Margaryan ◽  
Ismailov Azamat ◽  
Bekturdieva Ziba ◽  
Halmuratov Bayram ◽  
...  
Keyword(s):  
Susceptibility Testing ◽  
Drug Susceptibility ◽  
Drug Susceptibility Testing ◽  
Tuberculosis Patients

scholarly journals Comparison of Proportion and Resistance Ratio Methods for Drug Susceptibility Testing of Mycobacterium tuberculosis Isolated from Patients Attending National Tuberculosis Centre, Nepal

2010 ◽  
Vol 5 (1) ◽  
pp. 13-20
Author(s):  
S Acharya ◽  
P Ghimire ◽  
DK Khadka ◽  
S Nepali
Keyword(s):  
Mycobacterium Tuberculosis ◽  
Fluorescence Microscopy ◽  
Susceptibility Testing ◽  
Drug Susceptibility ◽  
Drug Susceptibility Testing ◽  
Resistance Ratio ◽  
National Tuberculosis ◽  
Smear Negative ◽  
Culture Positive ◽  
Good Agreement

Background: Tuberculosis (TB) is among the most serious infectious cause of global morbidity and mortality. Emergence of Multi-drug resistant tuberculosis (MDR-TB) is posing an increased threat to TB control programs. Drug susceptibility testing (DST) of Mycobacterium tuberculosis (M. tuberculosis) isolates is important for tackling such problems. Setting: National Tuberculosis Centre (NTC), Thimi, Bhaktapur, Nepal. Objectives: Comparative evaluation of two in vitro DST methods in determining susceptibility of M. tuberculosis isolates from patients attending NTC, to front-line anti-TB drugs: (Isoniazid-INH, Rifampicin-RFP, Streptomycin-SM, and Ethambutol-EMB). Methodology: This study was conducted from Sep 2006-Jun 2007. A total of 862 sputum samples (diagnosis or follow up cases) collected from patients (type of patients or their categories was not differentiated in this study) attending NTC bacteriology lab for sputum direct smear microscopy were analyzed using fluorescence microscopy. All smear positive samples, smear negative samples requested for culture were cultured. All culture positive samples confirmed as M. tuberculosis by biochemical tests were processed for DST by both proportion (PR) and resistance ratio (RR) methods. Results: Out of 862 sputum samples analyzed, 226 (26.2%) samples were positive for Acid Fast Bacilli (AFB) by fluorescence microscopy. Among 323 samples 226 smear positive samples and 97 smear negative samples requested for culture), 221 (68.4%) were culture positive, 92 (28.5%) were culture negative and 10 (3.1%) were contaminated. Out of 221 isolates of M. tuberculosis, 57.5% were resistant to one or more drugs by the PR method and 56.6% by the RR method. Similarly, MDR isolates were 29.9% and 29% by PR and RR methods respectively. On correlation analysis using Mc Nemar Chi-square test, no significant difference between the two tests were observed (p>0.05). The results showed high agreement between both methods and agreement rates to INH, RFP, SM and EMB were 93.2%, 93.7%, 93.2% and 94.1% respectively. Similarly, the agreement rates between both methods using kappa analysis showed kappa (k) value of 0.86, 0.85, 0.86 and 0.84 for INH, RFP, SM and EMB respectively, which is believed to be good agreement between both methods (k=0.80 to 1.00: Very good agreement). Conclusion: In conclusion, this study showed that both the Proportion and Resistance ratio methods are equally good for determining drug susceptibility of M. tuberculosis. Keywords: Mycobacterium tuberculosis; Drug Susceptibility Testing; Proportion Method; Resistance Ratio Method. DOI: 10.3126/saarctb.v5i1.3078 SAARC J. Tuber. Lung Dis. HIV/AIDS 2008 Vol.5(1) 13-20

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