Drug Susceptibility Testing Data Research Articles

Clinicomycological Study of Dermatophyte Infections in Patients Attending Dermatology Outpatient Department in a Tertiary Care Hospital

Context: Dermatophytosis is a fungal disease characterized by the infection of skin, hair, and nails. There is an upsurge of complicated superficial dermatophytosis and an increase in the incidence of chronic, relapsing, recurrent cases in India that are also often unresponsive to conventional doses of drugs. Aims: The aim of this study was to study the prevalence of dermatophyte species in the particular study area and it is susceptibility to itraconazole, terbinafine, and fluconazole. Settings and Design: All dermatophytes isolates obtained were subjected to 10% KOH mount, fungal culture, and antifungal sensitivity testing for fluconazole, itraconazole, and terbinafine. Materials and Methods: Newly diagnosed cases of dermatophytosis without treatment for the past 3 months were included in the study. KOH preparation was observed and subjected to fungal culture. Then, the susceptibility of the dermatophytes to oral antifungals (itraconazole, terbinafine, and fluconazole) was done. Results: Out of 28 patients with tinea, 14 males and 12 females were tested KOH positive. Out of them, 23 patients showed positive for dermatophyte growth. In them, 15 isolates were Trichophyton mentagrophytes and 8 isolates were Trichophyton rubrum. Antifungal drug susceptibility testing data indicated that, for the two species, MIC of itraconazole ranged between 0.03 and 16 μg/ml, terbinafine between 0.03 and 16 μg/ml, and fluconazole between 0.25 and 64 μg/ml. Conclusions: The study provided information regarding the prevalent species of dermatophyte in our study area and it is high sensitivity to itraconazole compared to terbinafine and the lowest for fluconazole. This gives us guidance as to which antifungal to use empirically in our clinical practice to treat tinea infection.

Direct Detection of Fluoroquinolone Resistance in Sputum Samples from Tuberculosis Patients by High Resolution Melt Curve Analysis.

Multidrug-resistant tuberculosis (MDR-TB) requires treatment with fluoroquinolone (FLQ) drugs, however, the excessive use of FLQ has led to the rise of extensively drug-resistant TB. In 2019, ~ 20% of total MDR-TB cases were estimated to be resistant to FLQ drugs. In the present study, we developed and evaluated the utility of high-resolution melt curve analysis (HRM) for the rapid detection of FLQ-resistant Mycobacterium tuberculosis for the first time directly from sputum samples. A reference plasmid library was generated for the most frequently observed mutations of gyrA gene and was used to discriminate between mutant and wild-type samples in the FLQ-HRM assay. The developed assay was evaluated on n = 25 MDR M. tuberculosis clinical isolates followed by validation on archived sputum DNA (n = 88) using DNA sequencing as a gold standard. The FLQ-HRM assay showed a 100% sensitivity [95% Confidence Interval (CI): 71.5 to 100] and specificity (95% CI: 39.7 to 100) in smear-positive category, and a sensitivity of 88.9% (95% CI: 77.3 to 95.8) with 84.2% (95% CI: 60.4 to 96.6) specificity in smear-negative category. The assay showed a high level of concordance of ~ 90% (κ = 0.74) with DNA sequencing, however, we were limited by the absence of phenotypic drug susceptibility testing data. In conclusion, HRM is a rapid, cost-effective (INR150/USD1.83) and closed-tube method for direct detection of FLQ resistance in sputum samples including direct smear-negative samples.

Treatment of MDR-TB/HIV/CMV patients under individualized regimes of antimycobacterial therapy

BACKGROUND. Often in practice there are combinations of several diseases, or tuberculosis of the respiratory organs develops against the background of various comorbidities, including HIV.
 OBJECTIVE. To demonstrate best clinical practices for selecting the optimal individualized treatment regimen (ITR) in a patient with multidrug-resistant tuberculosis (MDR-TB) associated with HIV in the setting of severe immunosuppression and complicated by poor tolerability.
 MATERIALS AND METHODS. Presented clinical analysis of newly diagnosed generalized MDR-TB associated with HIV, treated for ITR for 9 months, which was assigned according to the World Health Organization step-by-step algorithm based on phenotypic drug susceptibility testing data. At the time of assessment, the patient was taking 273 doses of ITR. ITR required extended monitoring and selection during its first months of treatment, as it was accompanied by severe intolerance to antimycobacterial drugs.
 
 RESULTS AND DISCUSSION. The expressed adverse events of 3-4 degrees were managed at the expense of carrying out the strengthened clinical and laboratory monitoring and consultations of narrow experts that allowed to select optimum ITR and in addition to carry out symptomatic treatment. Such tactics led to the normalization of hematological parameters with the disappearance of clinical manifestations of other adverse events and provided high intermediate results of treatment at the 9th month of ITR. Steady negativity of smear and culture (from1st month of treatment), positive radiological dynamics and significant improvement of well-being were obtained.
 CONCLUSIONS. Management of patients with MDR-TB/HIV co-infection with severe immunosuppression in patients who are treated by ITR requires enhanced monitoring of adverse reactions and rapid changes in the composition of ITR and early symptomatic treatment to ensure better adherence to treatment and positive outcomes.

Bedaquiline safety, efficacy, utilization and emergence of resistance following treatment of multidrug-resistant tuberculosis patients in South Africa: a retrospective cohort analysis

BackgroundThis retrospective cohort study assessed benefits and risks of bedaquiline treatment in multidrug-resistant-tuberculosis (MDR-TB) combination therapy by evaluating safety, effectiveness, drug utilization and emergence of resistance to bedaquiline.MethodsData were extracted from a register of South African drug-resistant-tuberculosis (DR-TB) patients (Electronic DR-TB Register [EDRWeb]) for newly diagnosed patients with MDR-TB (including pre-extensively drug-resistant [XDR]-TB and XDR-TB and excluding rifampicin-mono-resistant [RR]-TB, as these patients are by definition not multidrug-resistant), receiving either a bedaquiline-containing or non-bedaquiline-containing regimen, at 14 sites in South Africa. Total duration of treatment and follow-up was up to 30 months, including 6 months’ bedaquiline treatment. WHO treatment outcomes within 6 months after end-of-treatment were assessed in both patient groups. Longer term mortality (up to 30 months from treatment start) was evaluated through matching to the South African National Vital Statistics Register. Multivariable Cox proportional hazards analyses were used to predict association between receiving a bedaquiline-containing regimen and treatment outcome.ResultsData were extracted from EDRWeb for 5981 MDR-TB patients (N = 3747 bedaquiline-treated; N = 2234 non-bedaquiline-treated) who initiated treatment between 2015 and 2017, of whom 40.7% versus 80.6% had MDR-TB. More bedaquiline-treated than non-bedaquiline-treated patients had pre-XDR-TB (27.7% versus 9.5%) and XDR-TB (31.5% versus 9.9%) per pre-2021 WHO definitions. Most patients with treatment duration data (94.3%) received bedaquiline for 6 months. Treatment success (per pre-2021 WHO definitions) was achieved in 66.9% of bedaquiline-treated and 49.4% of non-bedaquiline-treated patients. Death was reported in fewer bedaquiline-treated (15.4%) than non-bedaquiline-treated (25.6%) patients. Bedaquiline-treated patients had increased likelihood of treatment success and decreased risk of mortality versus non-bedaquiline-treated patients. In patients with evaluable drug susceptibility testing data, 3.5% of bedaquiline-susceptible isolates at baseline acquired phenotypic resistance. Few patients reported bedaquiline-related treatment-emergent adverse events (TEAEs) (1.8%), TEAE-related bedaquiline discontinuations (1.4%) and QTcF values > 500 ms (2.5%) during treatment.ConclusionData from this large cohort of South African patients with MDR-TB showed treatment with bedaquiline-containing regimens was associated with survival and effectiveness benefit compared with non-bedaquiline-containing regimens. No new safety signals were detected. These data are consistent with the positive risk–benefit profile of bedaquiline and warrant continued implementation in combination therapy for MDR-TB treatment.

Factors contributing to the high prevalence of multidrug-resistance/Rifampicin-resistance in patients with tuberculosis: an epidemiological cross sectional and qualitative study from Khabarovsk krai region of Russia

BackgroundGrowing prevalence of multidrug-resistant/Rifampicin-resistant tuberculosis (MDR/RR-TB; resistance to Isoniazid and Rifampicin/Isolated resistance to Rifampicin) is putting in jeopardy the WHO End TB strategy. This study aimed to identify factors contributing to the high prevalence of MDR/RR-TB in Khabarovsk krai region of Russia.MethodsA cross-sectional retrospective study was conducted, analyzing clinical, demographic, and drug susceptibility testing data on 1440 patients. As a source of raw data, the national electronic TB surveillance system was used. Anonymous data was collected on every patient diagnosed with TB in all healthcare facilities of the region from January 2018 to December 2019. Only patients with proven excretion of m. tuberculosis were included in the study. Factors associated with MDR/RR-TB were identified through logistic regression analysis, in conjunction with in-depth interviews with eight patients, five healthcare managers and five doctors.Findings2661 patients were identified with TB, 1440 were incorporated in the study based on inclusion criteria. Of these, 618 (42.9%) were identified with MDR/RR-TB. Patients with a history of imprisonment were 16.53 times (95% CI 5.37 to 50.88,) more likely to have MDR/RR-TB, whereas re-treatment patients were 2.82 times (95% CI 2.16 to 3.66) more likely to have MDR/RR-TB. Other influencing factors included presence of disability (AOR is 2.32, 95% CI 1.38 to 3.89), cavitary disease (AOR is 1.76, 95% CI 1.37 to 2.25), and retirement status (AOR 0.65, 95% CI 0.43 to 0.98, p = 0.042). Poor patient knowledge and understanding of the disease, progressive weariness of prolonged TB treatment, and inability hospitalize infectious patients without their consent were perceived by the interviewees as major influencing factors.ConclusionsIncarceration and treatment history, regardless of outcome, were identified as major factors influencing MDR/RR-TB prevalence. It is essential for the TB care system to eliminate legal loopholes, which deprive doctors of means to enforce quarantine procedures and epidemiological surveillance on infected patients, former and current inmates. Increasing people’s awareness of TB, early detection and appropriate treatment of patients with TB are needed for successfully combating MDR/RR-TB.

Continuous surveillance of drug-resistant TB burden in Rwanda: a retrospective cross-sectional study.

Since the roll-out of the Xpert MTB/RIF assay, continuous surveillance can provide an estimate of rifampicin-resistant TB (RR-TB) prevalence, provided high drug susceptibility testing (DST) coverage is achieved. We use national data from Rwanda to describe rifampicin DST coverage, estimate the prevalence of RR-TB and assess its predictors. Routinely collected DST data were entered into an electronic TB case-based surveillance system. DST coverage was calculated among all bacteriologically confirmed pulmonary TB patients notified from 1 July 2019 to 30 June 2020 in Rwanda. The prevalence of RR-TB was estimated among those with DST results. Univariable and multivariable analysis was performed to explore predictors for RR TB. Among 4066 patients with bacteriologically confirmed pulmonary TB, rifampicin DST coverage was 95.6% (4066/4251). RR-TB was diagnosed in 73 patients. The prevalence of RR-TB was 1.4% (53/3659; 95% CI 1.09 to 1.89%) and 4.9% (20/406; 95% CI 3.03 to 7.51%) in new and previously treated TB cases, respectively. Predictors of RR-TB were: (1) living in Kigali City (adjusted OR [aOR] 1.65, 95% CI 1.03 to 2.65); (2) previous TB treatment (aOR 3.64, 95% CI 2.14 to 6.19); and (3) close contact with a known RR-TB patient (aOR 11.37, 95% CI 4.19 to 30.82). High rifampicin DST coverage for routine reporting allowed Rwanda to estimate the RR-TB prevalence among new and previously treated patients.

The 2021 WHO catalogue of Mycobacterium tuberculosis complex mutations associated with drug resistance: a genotypic analysis

BackgroundMolecular diagnostics are considered the most promising route to achieving rapid, universal drug susceptibility testing for Mycobacterium tuberculosiscomplex (MTBC). We aimed to generate a WHO endorsed catalogue of mutations to serve as a global standard for interpreting molecular information for drug resistance prediction.MethodsA candidate gene approach was used to identify mutations as associated with resistance, or consistent with susceptibility, for 13 WHO endorsed anti-tuberculosis drugs. 38,215 MTBC isolates with paired whole-genome sequencing and phenotypic drug susceptibility testing data were amassed from 45 countries. For each mutation, a contingency table of binary phenotypes and presence or absence of the mutation computed positive predictive value, and Fisher’s exact tests generated odds ratios and Benjamini-Hochberg corrected p-values. Mutations were graded as Associated with Resistance if present in at least 5 isolates, if the odds ratio was >1 with a statistically significant corrected p-value, and if the lower bound of the 95% confidence interval on the positive predictive value for phenotypic resistance was >25%. A series of expert rules were applied for final confidence grading of each mutation.Findings15,667 associations were computed for 13,211 unique mutations linked to one or more drugs. 1,149/15,667 (7·3%) mutations were classified as associated with phenotypic resistance and 107/15,667 (0·7%) were deemed consistent with susceptibility. For rifampicin, isoniazid, ethambutol, fluoroquinolones, and streptomycin, the mutations’ pooled sensitivity was >80%. Specificity was over 95% for all drugs except ethionamide (91·4%), moxifloxacin (91·6%) and ethambutol (93·3%). Only two resistance mutations were classified for bedaquiline, delamanid, clofazimine, and linezolid as prevalence of phenotypic resistance was low for these drugs.InterpretationThis first WHO endorsed catalogue of molecular targets for MTBC drug susceptibility testing provides a global standard for resistance interpretation. Its existence should encourage the implementation of molecular diagnostics by National Tuberculosis Programmes.FundingUNITAID, Wellcome, MRC, BMGF.

Etiological prevalence and antifungal sensitivity patterns of dermatophytosis in India - A multicentric study.

The prevalence of dermatophytes varies with season, geographical area, socio-economic factors and effective management strategies. The aim of the study was to assess the prevalence of pathogenic dermatophytes, clinical types of dermatophyte fungal infection, and in vitro antifungal drug susceptibility testing against dermatophytes. Three hundred and ninety five patients with dermatophytosis were enrolled from five cities (Mumbai, Delhi, Lucknow, Kolkata and Hyderabad) across India. All patients were subjected to clinical examination and investigations, including potassium hydroxide microscopy, fungal culture and antifungal drug susceptibility testing. Trichophyton rubrum was the most common species identified (68.4%), followed by T. mentagrophytes (29.3%). Within species, T. mentagrophytes was prevalent in humid environmental conditions (Mumbai and Kolkata), whereas T. rubrum was prevalent in noncoastal areas (Delhi, Lucknow and Hyderabad). Tinea corporis (71.4%) and tinea cruris (62.0%) were the common clinical types observed. antifungal drug susceptibility testing data indicated that minimum inhibitory concentration required to inhibit the growth of 90% of organisms (MIC-90) was lowest for griseofulvin (0.25-3.0 μg/mL). Among oral antifungals, the mean MIC of itraconazole was within the range (0.84 [0.252] μg/ mL), whereas high mean MIC values were reported for terbinafine (0.05 [0.043] μg/mL). Among topical agents, lowest mean MIC values were reported for luliconazole (0.29 [0.286] μg/mL), eberconazole (0.32 [0.251]) μg/mL and amorolfine (0.60 [0.306]) μg/mL. Lack of correlation between in vitro antifungal susceptibility and clinical outcome and absence of defined MIC breakpoints. T. rubrum was the most common, followed by T. mentagrophytes as an emerging/codominant fungal isolate in India. Tinea corporis was the most common clinical type of dermatophytosis. Mean MIC of terbinafine was above the reference range, while it was within the range for itraconazole; griseofulvin had the lowest mean MIC. Luliconazole presented the lowest mean MIC values across cities.

Towards Unified Data Exchange Formats for Reporting Molecular Drug Susceptibility Testing.

With the rapid development of new advanced molecular detection methods, identification of new genetic mutations conferring pathogen resistance to an ever-growing variety of antimicrobial substances will generate massive genomic datasets for public health and clinical laboratories. Keeping up with specialized standard coding for these immense datasets will be extremely challenging. This challenge prompted our effort to create a common molecular resistance Logical Observation Identifiers Names and Codes (LOINC) panel that can be used to report any identified antimicrobial resistance pattern. To develop and utilize a common molecular resistance LOINC panel for molecular drug susceptibility testing (DST) data exchange in the U.S. National Tuberculosis Surveillance System using California Department of Public Health (CDPH) and New York State Department of Health as pilot sites. We developed an interface and mapped incoming molecular DST data to the common molecular resistance LOINC panel using Health Level Seven (HL7) v2.5.1 Electronic Laboratory Reporting (ELR) message specifications through the Orion Health™ Rhapsody Integration Engine v6.3.1. Both pilot sites were able to process and upload/import the standardized HL7 v2.5.1 ELR messages into their respective systems; albeit CDPH identified areas for system improvements and has focused efforts to streamline the message importation process. Specifically, CDPH is enhancing their system to better capture parent-child elements and ensure that the data collected can be accessed seamlessly by the U.S. Centers for Disease Control and Prevention. The common molecular resistance LOINC panel is designed to be generalizable across other resistance genes and ideally also applicable to other disease domains. The study demonstrates that it is possible to exchange molecular DST data across the continuum of disparate healthcare information systems in integrated public health environments using the common molecular resistance LOINC panel.

Phylogenetically informative mutations in genes implicated in antibiotic resistance in Mycobacterium tuberculosis complex

BackgroundA comprehensive understanding of the pre-existing genetic variation in genes associated with antibiotic resistance in the Mycobacterium tuberculosis complex (MTBC) is needed to accurately interpret whole-genome sequencing data for genotypic drug susceptibility testing (DST).MethodsWe investigated mutations in 92 genes implicated in resistance to 21 anti-tuberculosis drugs using the genomes of 405 phylogenetically diverse MTBC strains. The role of phylogenetically informative mutations was assessed by routine phenotypic DST data for the first-line drugs isoniazid, rifampicin, ethambutol, and pyrazinamide from a separate collection of over 7000 clinical strains. Selected mutations/strains were further investigated by minimum inhibitory concentration (MIC) testing.ResultsOut of 547 phylogenetically informative mutations identified, 138 were classified as not correlating with resistance to first-line drugs. MIC testing did not reveal a discernible impact of a Rv1979c deletion shared by M. africanum lineage 5 strains on resistance to clofazimine. Finally, we found molecular evidence that some MTBC subgroups may be hyper-susceptible to bedaquiline and clofazimine by different loss-of-function mutations affecting a drug efflux pump subunit (MmpL5).ConclusionsOur findings underline that the genetic diversity in MTBC has to be studied more systematically to inform the design of clinical trials and to define sound epidemiologic cut-off values (ECOFFs) for new and repurposed anti-tuberculosis drugs. In that regard, our comprehensive variant catalogue provides a solid basis for the interpretation of mutations in genotypic as well as in phenotypic DST assays.

The clinical significance of Mycobacterium triplex.

Mycobacterium triplex is a slow-growing nontuberculous mycobacteria (NTM) and is a rare cause of human disease. The pathogenicity, natural history and spectrum of disease is unknown. The aim of this study was to review the clinical features, outcomes and drug susceptibility testing (DST) of all M. triplex isolates in Queensland, Australia to guide management of this rare NTM infection in the future. This retrospective study included all patients who isolated M. triplex in Queensland, Australia from the 1st January 2000 to 31st December 2016. Clinical information was obtained from medical records to determine the clinical significance of isolates, natural history of disease and treatment outcomes. DST was performed on 15 isolates. Forty-three patients (21 male) had positive cultures for M. triplex. Thirty-nine patients had isolates from pulmonary specimens and 17 (43.6%) met the American Thoracic Society criteria for NTM lung disease. Six patients with pulmonary infection received antimicrobial therapy with 5 patients demonstrating treatment success. Four patients had localised extrapulmonary disease and were cured with surgical management ± antimicrobial therapy. DST suggests 93% of isolates are susceptible to macrolides. This is the largest case series of M. triplex isolates and confirms it is a rare human pathogen. Extrapulmonary disease responded well to surgical management. Treatment of M. triplex pulmonary disease is challenging, and the optimal antimicrobial regimen is unknown. However, the DST data suggests macrolide resistance is rare and macrolides should be included in treatment regimens.

Integrating standardized whole genome sequence analysis with a global Mycobacterium tuberculosis antibiotic resistance knowledgebase

Drug-resistant tuberculosis poses a persistent public health threat. The ReSeqTB platform is a collaborative, curated knowledgebase, designed to standardize and aggregate global Mycobacterium tuberculosis complex (MTBC) variant data from whole genome sequencing (WGS) with phenotypic drug susceptibility testing (DST) and clinical data. We developed a unified analysis variant pipeline (UVP) (https://github.com/CPTR-ReSeqTB/UVP) to identify variants and assign lineage from MTBC sequence data. Stringent thresholds and quality control measures were incorporated in this open source tool. The pipeline was validated using a well-characterized dataset of 90 diverse MTBC isolates with conventional DST and DNA Sanger sequencing data. The UVP exhibited 98.9% agreement with the variants identified using Sanger sequencing and was 100% concordant with conventional methods of assigning lineage. We analyzed 4636 publicly available MTBC isolates in the ReSeqTB platform representing all seven major MTBC lineages. The variants detected have an above 94% accuracy of predicting drug based on the accompanying DST results in the platform. The aggregation of variants over time in the platform will establish confidence-graded mutations statistically associated with phenotypic drug resistance. These tools serve as critical reference standards for future molecular diagnostic assay developers, researchers, public health agencies and clinicians working towards the control of drug-resistant tuberculosis.

Improving the Quality of Data Exchange Formats in the U.S. National Tuberculosis Surveillance System

Objective: The objective of this presentation is to use a congruence of standardization protocols to effectively ensure that the quality of the data elements and exchange formats within the NTSS are optimal for users of the system.Introduction: Disease surveillance systems remain the best quality systems to rely on when standardized surveillance systems provide the best data to understand disease occurrence and trends. The United States National Tuberculosis Surveillance System (NTSS) contains reported tuberculosis (TB) cases provided by all 50 states, the District of Columbia (DC), New York City, Puerto Rico, and other U.S.-affiliated jurisdictions in the Pacific Ocean and Caribbean Sea [1]. However, the NTSS currently captures phenotypic drug susceptibility testing (DST) data and does not have the ability to collect the rapid molecular DST data generated by platforms such as Cepheid GeneXpert MTB/RIF, Hain MTBDRplus and MTBDRsl, Pyrosequencing, and Whole Genome Sequencing [2-6]. Moreover, the information exchanges within the NTSS (represented in HL7 v2.5.1 [7]) are missing critical segments for appropriately representing laboratory test results and data on microbiological specimens.Methods: The application of the standardization protocols involves: (a) the revision of the current Report of Verified Case of Tuberculosis (RCVT) form to include the collection of molecular DST data; (b) the enhancement of the TB Case Notification Message Mapping Guide (MMG) v2.03 [8] to include segments for appropriately reporting laboratory test results (i.e., using Logical Observation Identifiers Names and Codes (LOINC) as a recommended vocabulary) and microbiology related test results (i.e., using Systematized Nomenclature of Medicine -- Clinical Terms (SNOMED CT) as a recommended vocabulary); and (c) the standardization of the laboratory testing results generated by the variety of molecular DST platforms, reported to TB health departments through electronic laboratory results (ELR), using those same standardized LOINC and SNOMED CT vocabularies in HL7 v2.5.1 [7].Results: The application of the standardization protocols would optimize early detection and reporting of rifampin-resistant TB cases; provide a high-quality data-driven decision-making process by public health administrators on TB cases; and generate high-quality datasets to enhance reporting or analyses of TB surveillance data and drug resistance.Conclusions: This study demonstrates that it is possible to apply standardized protocols to improve the quality of data, specifications and exchange formats within the NTSS, thereby streamlining the seamless exchange of TB incident cases in an integrated public health environment supporting TB surveillance, informatics, and translational research.

Outcomes of standard and tailored anti-tuberculosis regimens in patients with tuberculous pleural effusion.

In an era of increasing concerns about drug resistance, there are limited data on treatment outcomes and recurrence rates after standard short-course anti-tuberculosis treatment in patients with culture-negative tuberculous pleural effusion (TPE). To compare treatment outcomes and recurrence rates between a standard anti-tuberculosis regimen with negative culture and unavailable drug susceptibility testing (DST) data, and a tailored anti-tuberculosis regimen based on individual DST data. We analysed the data of all patients with TPE from the TB registry database at Kyungpook National University Hospital, South Korea, during 2008-2012. The study population was divided into two groups according to regimen. Standard and tailored anti-tuberculosis regimens were administered to respectively 124 and 146 patients with TPE. Drug resistance was detected in 10% of patients with TPE, about a quarter of whom were multidrug-resistant. The treatment completion rate was not significantly different between the two groups (91% vs. 93%). During a median 20-month follow-up, the recurrence rate was also similar in both groups (1% vs.1%). Despite limited statistical power, these preliminary results support the hypothesis that immunocompetent patients with culture-negative TPE can be appropriately managed with a standard short-course anti-tuberculosis regimen, even in this era of increasing concerns about drug resistance.

Drug Susceptibility Patterns in MDR-TB Patients: Challenges for Future Regimen Design. A Cross-Sectional Study.

Globally, there is substantial concern regarding the challenges of treating complex drug resistance patterns in multidrug resistant tuberculosis cases. Utilising data from three different settings (Estonia, Latvia, Romania) we sought to contrast drug susceptibility profiles for multidrug resistant tuberculosis cases, highlight the difficulties in designing universal regimen, and inform future regimen selection. Demographic and microbiological surveillance data for multidrug resistant tuberculosis cases from 2004–13 were analysed. High levels of additional resistance to currently recommended second line drugs were seen in all settings, with extensive variability between countries. Accurate drug susceptibility testing and drug susceptibility testing data are vital to inform the development of comprehensive, flexible, multidrug resistant tuberculosis guidance.

Proficiency of drug susceptibility testing of Mycobacterium tuberculosis against pyrazinamide: the Swedish experience

Pyrazinamide (PZA) is a key drug in the treatment of tuberculosis (TB), including multidrug-resistant TB. Drug susceptibility testing (DST) of Mycobacterium tuberculosis against PZA is not included in the World Health Organization's yearly proficiency testing. There is an increasing need to establish quality control of PZA DST. To evaluate the performance of PZA DST and to introduce a quality assurance system for the test in Sweden. Panels with PZA-susceptible and -resistant isolates were used in three rounds of proficiency testing in all five Swedish clinical TB laboratories and our reference laboratory. All laboratories used the MGIT 960 system. Minimum inhibitory concentrations (MICs) were determined and the pncA gene was sequenced to further characterise the 52 panel strains. Good agreement was seen between the phenotypic PZA DST and pncA sequence data, and MIC determination confirmed high levels of resistance. However, in contrast to other drugs, for which correct proficiency test results were observed, specificity problems occurred for PZA DST in some laboratories. In Sweden, using panel testing, differences were seen in the proficiency of TB laboratories in correctly identifying PZA susceptibility. Improved results were noted in the third round; PZA has therefore been included in yearly proficiency testing.

Detection of mutations associated with multidrug-resistantMycobacterium tuberculosisclinical isolates

Antimicrobial resistance was studied in 100 Mycobacterium tuberculosis strains selected randomly from sputum cultures of newly diagnosed tuberculosis patients. Resistance of the isolates to rifampicin, isoniazid, and ethambutol was tested by both drug susceptibility testing (DST) and allele-specific PCR (AS-PCR). A total of 19 (19%) isolates were found resistant to at least one of the antituberculosis drugs investigated by PCR compared with 14 (14%) resistant isolates detected by DST. Eleven mutations were detected by AS-PCR in the rpoB gene (codons 516, 526, and 531), associated with rifampicin resistance, a marker of multidrug-resistant tuberculosis (MDR-TB), 14 mutations in the katG gene codon 315 that confers resistance to isoniazid, and nine mutations in the embB gene codon 306 that confers resistance to ethambutol. Mutations in the six multidrug-resistant isolates were confirmed by DNA sequencing. Results were compared with phenotypic DST data. Nineteen different mutation types to at least one of the drugs were found; six isolates (6%) were classified as MDR-TB, defined as resistance to at least rifampicin and isoniazid. The rates of concordance of the PCR with the phenotypic susceptibility test were 71.4, 54.5, and 44.4 for isoniazid, rifampicin, and ethambutol, respectively. These results highlight the importance of molecular epidemiology studies of tuberculosis in understudied regions with a tuberculosis burden to uncover the true prevalence of the MDR-TB.

Molecular characterization of drug-resistant Mycobacterium tuberculosis isolates from Ontario, Canada

Ontario bears the greatest burden of tuberculosis in Canada, with 40% of all cases and 60% of multidrug-resistant cases. The purpose of this study was to genotypically characterize isoniazid- and rifampicin-resistant isolates and compare these results with phenotypic drug susceptibility testing data. This is the first Canadian study to examine gene mutations that contribute to multidrug-resistant tuberculosis. A total of 751 tuberculosis isolates were tested for drug resistance using phenotypic antimicrobial susceptibility testing methods. Isolates were then characterized using molecular methods. Following DNA extraction, PCR amplification and sequence analysis were performed on the rifampicin resistance region of rpoB, as well as the region surrounding katG315 and the inhA promoter region associated with isoniazid resistance. Eighteen different mutation types were found in the rpoB region of rifampicin-resistant isolates. Isolates with mutations at residues rpoB531 (64.1%), rpoB526 (15.2%) and rpoB516 (8.7%) were the most common. In addition, an insertion was found at residue 514. Three phenotypically rifampicin-resistant isolates (3.3%) were genotypically wild-type. In isoniazid-resistant strains, mutations were found most commonly at katG315 (45.4%) as well as at the inhA promoter region (28.6%). Thirty-nine isolates (25.3%) were phenotypically isoniazid-resistant but genotypically wild-type. The katG315 mutation was statistically associated with multidrug-resistant isolates. This study expands the knowledge of mutations that potentially contribute to drug resistance in tuberculosis and lays the foundation for developing molecular-based tests to determine drug resistance in clinical tuberculosis isolates.

A Trend in Acquired Drug Resistances of Tuberculosis Patients Registered in Health Centers from 1981 to 2004

Background : The drug resistance rate in tuberculosis patients with history of chemotherapy is an important indicator of for evaluation of appropriateness of treatment regimens and compliance of patients. This study examined the long-term changes in the drug resistance rates among TB patients failed in treatment or reactivated. Methods : The results of drug susceptibility testing data from patients registered in health centers from 1981 to 2004 were analyzed. Results : The rate of resistance to isoniazid decreased from 90% to 20%, and the resistance to ethambutol decreased from 45% to 6%. The rate of resistance to rifampicin varied from 13% to 28% and the resistance to pyrazinamide was 5% to 10%. Multidrug resistance was about 2-3% lower than any rifampicin resistance rates. The second-line drug resistance was ranged from 1% to 3%. There was no difference between patients' genders. Patient numbers per 100,000 population increased with age. The regional distribution was even at 4-6 patients per 100,000 population, and drug resistance rates were significantly lower in big city areas than in small towns and rural areas. Conclusion : The rates of resistance of Mycobacterium tuberculosis isolated from TB patients with history of chemotherapy to isoniazid, rifampin, ethambutol, and isoniazid plus rifampin were significantly decreased during over two decades.