Clinical characteristics and treatment outcomes of patients with isoniazid-monoresistant tuberculosis

The Mycobacterium tuberculosis genome at 25 years: lessons and lingering questions

First achieved in 1998 by Cole et al., the complete genome sequence of Mycobacterium tuberculosis continues to provide an invaluable resource to understand tuberculosis (TB), the leading cause of global infectious disease mortality. At the 25-year anniversary of this accomplishment, we describe how insights gleaned from the M. tuberculosis genome have led to vital tools for TB research, epidemiology, and clinical practice. The increasing accessibility of whole-genome sequencing across research and clinical settings has improved our ability to predict antibacterial susceptibility, to track epidemics at the level of individual outbreaks and wider historical trends, to query the efficacy of the bacille Calmette-Guérin (BCG) vaccine, and to uncover targets for novel antitubercular therapeutics. Likewise, we discuss several recent efforts to extract further discoveries from this powerful resource.

Poor treatment outcome and associated risk factors among patients with isoniazid mono-resistant tuberculosis: A systematic review and meta-analysis

BACKGROUND

To date, isoniazid mono-resistant tuberculosis (TB) is becoming an emerging global public health problem. It is associated with poor treatment outcome. Different studies have assessed the treatment outcome of isoniazid mono-resistant TB cases, however, the findings are inconsistent and there is limited global comprehensive report. Thus, this study aimed to assess the poor treatment outcome and its associated risk factors among patients with isoniazid mono-resistant TB.

METHODS

Studies that reported the treatment outcomes and associated factors among isoniazid mono-resistant TB were searched from electronic databases and other sources. We used Joana Briggs Institute critical appraisal tool to assess the study's quality. We assessed publication bias through visual inspection of the funnel plot and confirmed by Egger's regression test. We used STATA version 17 for statistical analysis.

RESULTS

Among 347 studies identified from the whole search, data were extracted from 25 studies reported from 47 countries. The pooled successful and poor treatment outcomes were 78% (95%CI; 74%-83%) and 22% (95%CI; 17%-26%), respectively. Specifically, complete, cure, treatment failure, mortality, loss to follow-up and relapse rates were 34%(95%CI; 17%-52%), 62% (95%CI; 50%-73%), 5% (95%CI; 3%-7%), 6% (95%CI; 4%-8%), 12% (95%CI; 8%-17%), and 1.7% (95%CI; 0.4%-3.1%), respectively. Higher prevalence of pooled poor treatment outcome was found in the South East Asian Region (estimate; 40%, 95%C; 34%-45%), and African Region (estimate; 33%, 95%CI; 24%-42%). Previous TB treatment (OR; 1.74, 95%CI; 1.15-2.33), having cancer (OR; 3.53, 95%CI; 1.43-5.62), and being initially smear positive (OR; 1.26, 95%CI; 1.08-1.43) were associated with poor treatment outcome. While those patients who took rifampicin in the continuation phase (OR; 0.22, 95%CI; 0.04-0.41), had extrapulmonary TB (OR; 0.70, 95%CI; 0.55-0.85), and took second-line injectable drugs (OR; 0.54, 95%CI; 0.33-0.75) had reduced risk of poor treatment outcome.

CONCLUSION

Isoniazid mono-resistant TB patients had high poor treatment outcome. Thus, determination of isoniazid resistance pattern for all bacteriologically confirmed TB cases is critical for successful treatment outcome. PROSPERO registration number: CRD42022372367.

A Retrospective Analysis of Clinico-Demographic and Genetic Characteristics and Treatment Outcomes in Isoniazid Mono-Resistant Tuberculosis Patients: A Single-Center Study

INTRODUCTION

Treatment failure and relapse rates are more likely to occur when there is isoniazid (INH) resistance. So, we can no longer ignore the problem of isoniazid mono-resistance. It is pertinent to control the spread of primary INH resistance and prevent secondary resistance.

AIM

This study aims to evaluate subjects' clinical, demographic, and genetic characteristics and explore their treatment outcomes.

METHODS

All data of isoniazid mono-resistant tuberculosis (TB) patients, which were maintained in the electronic database of mandatory notifications (NIKSHAY Portal) between 2017 and 2022, were reviewed. A total of 54 patients were included after excluding five patients with ongoing treatment.

RESULTS

Of 54 patients, 41 (75.9%) were cured, which was classified under favorable outcome, and the rest were classified under unfavorable outcome. Phenotypic, high-level mutation (katG) was found in 48 (88.9%) patients. Kaplan-Meier curves show that survival probabilities increase in weeks with regular intake of drugs.

CONCLUSION

Our study found that those with younger ages and males were more affected. We found favorable outcomes in the majority of patients.

Effectiveness and safety of Levofloxacin containing regimen in the treatment of Isoniazid mono-resistant pulmonary Tuberculosis: a systematic review

Background

We aimed to determine the effectiveness and safety of the Levofloxacin-containing regimen that the World Health Organization is currently recommending for the treatment of Isoniazid mono-resistant pulmonary Tuberculosis.

Methods

Our eligible criteria for the studies to be included were; randomized controlled trials or cohort studies that focused on adults with Isoniazid mono-resistant tuberculosis (HrTB) and treated with a Levofloxacin-containing regimen along with first-line anti-tubercular drugs; they should have had a control group treated with first-line without Levofloxacin; should have reported treatment success rate, mortality, recurrence, progression to multidrug-resistant Tuberculosis. We performed the search in MEDLINE, EMBASE, Epistemonikos, Google Scholar, and Clinical trials registry. Two authors independently screened the titles/abstracts and full texts that were retained after the initial screening, and a third author resolved disagreements.

Results

Our search found 4,813 records after excluding duplicates. We excluded 4,768 records after screening the titles and abstracts, retaining 44 records. Subsequently, 36 articles were excluded after the full-text screening, and eight appeared to have partially fulfilled the inclusion criteria. We contacted the respective authors, and none responded positively. Hence, no articles were included in the meta-analysis.

Conclusion

We found no "quality" evidence currently on the effectiveness and safety of Levofloxacin in treating HrTB.

Systematic review registration

https://www.crd.york.ac.uk/prospero/display_record.php?ID=CRD42022290333, identifier: CRD42022290333.

The Clinical Experience of Mycobacterial Culture Yield of Pleural Tissue by Pleuroscopic Pleural Biopsy among Tuberculous Pleurisy Patients

Background and Objectives: Tuberculous pleurisy is a common extrapulmonary TB that poses a health threat. However, diagnosis of TB pleurisy is challenging because of the low positivity rate of pleural effusion mycobacterial culture and difficulty in retrieval of optimal pleural tissue. This study aimed to investigate the efficacy of mycobacterial culture from pleural tissue, obtained by forceps biopsy through medical pleuroscopy, in the diagnosis of TB pleurisy. Materials and Methods: This study retrospectively enrolled 68 TB pleurisy patients. Among them, 46 patients received semi-rigid pleuroscopy from April 2016 to March 2021 in a tertiary hospital. We analyzed the mycobacterial culture from pleural tissue obtained by forceps biopsy. Results: The average age of the study participants was 62.8 years, and 64.7% of them were men. In the pleuroscopic group, the sensitivity of positive Mycobacterium tuberculosis (M. TB) cultures for sputum, pleural effusion, and pleural tissue were 35.7% (15/42), 34.8% (16/46), and 78.3% (18/23), respectively. High sensitivities of M. TB culture from pleural tissue were up to 94.4% and 91.7% when pleural characteristic patterns showed adhesion lesions and both adhesion lesions and presence of micronodules, respectively. Conclusions: M. TB culture from pleural tissue should be considered a routine test when facing unknown pleural effusion during pleuroscopic examination.

Characteristics and Treatment Outcomes of Isoniazid Mono-Resistant Tuberculosis: A Retrospective Study

PURPOSE

Isoniazid (INH) mono-resistant tuberculosis (Hr-TB) is a highly prevalent type of drug-resistant TB, possibly associated with unfavorable treatment outcomes. However, definitive guidelines on an optimal treatment regimen and duration for Hr-TB are currently under discussion. We evaluated the characteristics and treatment outcomes of Hr-TB patients.

MATERIALS AND METHODS

We retrospectively reviewed the medical records of Hr-TB patients treated at a South Korean tertiary referral hospital from January 2005 to December 2018.

RESULTS

We included 195 Hr-TB patients. 113 (57.9%) were male, and the median age was 56.6 [interquartile range, 40.2-68.6] years. Mutations in katG were the most frequent [54 (56.3%)], followed by those in the inhA [34 (35.4%)]. Favorable and unfavorable outcomes were noted in 164 (84.1%) and 31 (15.9%) patients, respectively. Smoking history [odds ratio (OR)=5.606, 95% confidence interval (CI): 1.695-18.543, p=0.005], low albumin level (OR=0.246, 95% CI: 0.104-0.578, p=0.001), and positive acid-fast bacilli culture at 2 months (OR=7.853, 95% CI: 1.246-49.506, p=0.028) were associated with unfavorable outcomes.

CONCLUSION

A tailored strategy targeting high-risk patients is imperative for improved treatment outcomes. Further research on the rapid and accurate detection of resistance to INH and other companion drugs is warranted.

Treatment outcomes and factors associated with unfavourable outcome among previously treated tuberculosis patients with isoniazid resistance in four regions of Cameroon

Introduction

it is unclear what the optimal treatment regimen for previously treated patients with rifampicin-susceptible isoniazid resistant tuberculosis should be. Conflicting evidence exists as to the effectiveness of the WHO standardized category II regimen in these patients. The objectives were to compare treatment outcomes between previously treated rifampicin-susceptible pulmonary tuberculosis patients with and without isoniazid resistance using the category II regimen and determine factors associated with an unfavourable outcome in those with isoniazid resistance in four regions of Cameroon.

Methods

we conducted a retrospective review of all bacteriologically confirmed previously treated rifampicin-susceptible patients with and without isoniazid resistance registered in four regions of Cameroon from January 2012 to March 2015.

Results

a total of 753 patients with a mean age of 38 ± 12 years including 498(66%) males were registered. Forty seven of the 753 had isoniazid-resistant TB, giving a prevalence of 6.2% (95% CI: 4.7-8.2). Treatment outcomes could only be ascertained for 733 patients as 20 (2.7%) were transferred out to other regions. Twenty-nine percent of patients with isoniazid resistance as against 21% of isoniazid susceptible patients had an unfavourable outcome (p = 0.32). In a multivariate logistic regression analysis, only HIV infection was significantly associated with an unfavourable outcome in isoniazid-resistant patients (p = 0.02).

Conclusion

treatment outcomes using WHO category II regimen in previously treated rifampicin -susceptible pulmonary tuberculosis patients with and without isoniazid resistance in four regions of Cameroon are similar. HIV infection is an independent risk factor for an unfavourable outcome in patients with rifampicin-susceptible isoniazid-resistant disease treated with this regimen.

Risk factors affecting treatment outcomes for pulmonary tuberculosis in Finland 2007-2014: a national cohort study

BACKGROUND

Major transition in tuberculosis (TB) epidemiology is taking place in many European countries including Finland. Monitoring treatment outcome of TB cases is important for identifying gaps in the national TB control program, in order to strengthen the system. The aim of the study was to identify potential risk factors for non-successful TB treatment outcomes, with a particular focus on the impact of comorbidities. We also evaluated the treatment outcome monitoring system.

METHODS

All notified microbiologically confirmed pulmonary TB cases in Finland in 2007-2014 were included, except multi-drug resistant (MDR) cases. Nationwide register data were retrieved from: Infectious Diseases Register, Population Register, Cause of Death Register and Hospital Discharge Register. Non-successful outcomes were divided into three groups: death, unsatisfactory outcomes and non-defined outcomes. Logistic regression analyses were used to identify risk factors for non-successful outcomes.

RESULTS

Treatment outcomes were notified for 98.6% of study cases (n = 1396/1416). Treatment success rate was 75%. The main reason for non-successful outcome was death (16%), whereas outcomes failed and lost to follow-up were rare (1% together). In a multivariable model, risk factors for death as outcome were increasing age, male gender and Charlson comorbidity index ≥1, for unsatisfactory outcomes non-MDR drug resistance and TB registered in the first study period, and for non-defined outcomes non-MDR drug resistance. Among 50 cases with unsatisfactory outcomes, we observed false outcome allocations in eight (16%), and > 2% of the cases transferred to another country or disappeared before or during treatment.

CONCLUSIONS

With a high proportion of older population among tuberculosis cases, death is a common treatment outcome in Finland. Comorbidity is an important factor to be incorporated when interpreting and comparing outcome rates. There was a considerable inconsistency in outcome allocation in the monitoring system, which implies that there is need to review the guidelines and provide further training for outcome assessment.

Isoniazid (INH) mono-resistance and tuberculosis (TB) treatment success: analysis of European surveillance data, 2002 to 2014

Introduction: Isoniazid (INH) is an essential drug for tuberculosis (TB) treatment. Resistance to INH may increase the likelihood of negative treatment outcome.

Aim: We aimed to determine the impact of INH mono-resistance on TB treatment outcome in the European Union/European Economic Area and to identify risk factors for unsuccessful outcome in cases with INH mono-resistant TB.

Methods: In this observational study, we retrospectively analysed TB cases that were diagnosed in 2002–14 and included in the European Surveillance System (TESSy). Multilevel logistic regression models were applied to identify risk factors and correct for clustering of cases within countries.

Results: A total of 187,370 susceptible and 7,578 INH mono-resistant TB cases from 24 countries were included in the outcome analysis. Treatment was successful in 74.0% of INH mono-resistant and 77.4% of susceptible TB cases. In the final model, treatment success was lower among INH mono-resistant cases (Odds ratio (OR): 0.7; 95% confidence interval (CI): 0.6–0.9; adjusted absolute difference in treatment success: 5.3%). Among INH mono-resistant TB cases, unsuccessful treatment outcome was associated with age above median (OR: 1.3; 95% CI: 1.2–1.5), male sex (OR: 1.3; 95% CI: 1.1–1.4), positive smear microscopy (OR: 1.3; 95% CI: 1.1–1.4), positive HIV status (OR: 3.3; 95% CI: 1.6–6.5) and a prior TB history (OR: 1.8; 95% CI: 1.5–2.2).

Conclusions: This study provides evidence for an association between INH mono-resistance and a lower likelihood of TB treatment success. Increased attention should be paid to timely detection and management of INH mono-resistant TB.

Risk factors for drug-resistant tuberculosis at a referral centre in Toronto, Ontario, Canada: 2010-2016

BACKGROUND

Drug-resistant tuberculosis (TB) poses a major public health concern worldwide. However, no studies have addressed risk factors for drug resistance in Ontario, which has its own unique profile of immigrants. We evaluated demographic and clinical risk factors for drug-resistant TB among patients treated at West Park Healthcare Centre, located in Toronto, Ontario (Canada).

METHODS

All patients who were diagnosed with TB and treated at West Park Healthcare Centre between January 2010 and December 2016 were included in this retrospective cohort study. Characteristics of patients with isoniazid mono-resistant (INH-R) TB and multidrug resistant (MDR) TB were compared to patients with drug-susceptible TB with bivariate and multivariable logistic regression.

RESULTS

Risk factors for INH-R TB included younger age (younger than 35 years), prior TB treatment, non-diabetic and birth in a non-South-East Asian country, but only the latter two factors were significant in multivariable analysis. On the other hand, we found younger generation (younger than 65 years), birth in European region, recent arrival to Canada (fewer than 120 months), prior treatment and human immunodeficiency virus (HIV) infection were associated with MDR-TB, among which younger age (younger than 35 years), more recent immigration (fewer than 24 months), prior treatment and HIV infection were significant in multivariable analysis.

CONCLUSION

These findings may be of use to TB clinicians in the province by informing the initial empiric antibiotic regimen prescribed while awaiting phenotypic drug susceptibility testing and assisting in decisions regarding whether to request rapid molecular drug susceptibility testing.

Incidence, treatment, and outcomes of isoniazid mono-resistant Mycobacterium tuberculosis infections in Alberta, Canada from 2007-2017

Isoniazid resistant Mycobacterium tuberculosis (Hr-TB) is the most frequently encountered TB resistance phenotype in North America but limited data exist on the effectiveness of current therapeutic regimens. Ineffective treatment of Hr-TB increases patient relapse and anti-mycobacterial resistance, specifically MDR-TB. We undertook a multi-centre, retrospective review of culture-positive Hr-TB patients in Alberta, Canada (2007-2017). We assessed incidence and treatment outcomes, with a focus on fluoroquinolone (FQ)-containing regimens, to understand the risk of unsuccessful outcomes. Rates of Hr-TB were determined using the mid-year provincial population and odds of unsuccessful treatment was calculated using a Fisher's Exact test. One hundred eight patients of median age 37 years (IQR: 26-50) were identified with Hr-TB (6.3%), 98 of whom were able to be analyzed. Seven percent reported prior treatment. Rate of foreign birth was high (95%), but continent of origin did not predict Hr-TB (p = 0.47). Mean compliance was 95% with no difference between FQ and non-FQ regimens (p = 1.00). Treatment success was high (91.8%). FQ-containing regimens were frequently initiated (70%), with no difference in unsuccessful outcomes compared to non-FQ-containing regimens (5.8% vs. 13.8%, OR 0.4, 95% CI 0.1-2.3, p = 0.23). Only one patient (1%) utilizing a less common non-FQ-based regimen including two months of pyrazinamide developed secondary multidrug resistance. Unsuccessful treatment was low (<10%) relative to comparable literature (~15%) and showed similar outcomes for FQ and non-FQ-based regimens and no deficit to those using intermittent fluoroquinolones in the continuation phase of treatment. Our findings are similar to recent data, however prospective, randomized trials of adequate power are needed to determine the optimal treatment for Hr-TB.

Isoniazid-resistant Mycobacterium tuberculosis: prevalence, resistance spectrum and genetic determinants of resistance

The lack of simple, rapid diagnostic tests for isoniazid-resistant rifampicin-susceptible tuberculosis infection (Hr-TB) can result in low treatment efficacy and further amplification of drug resistance. Based on the clinical data, this study sought to estimate the prevalence of Hr-TB in the general population and characterize the phenotypic susceptibility and genetic determinants of isoniazid resistance in M. tuberculosis strains. Molecular-genetic and culture-based drug susceptibility tests were performed on M. tuberculosis isolates and M. tuberculosis DNA obtained from the patients with pulmonary TB undergoing treatment at the Central Tuberculosis Research Institute between 2011 and 2018. The tests revealed that Hr-TB accounted for 12% of all TB cases in the studied sample. Hr-TB strains were either resistant to isoniazid only (45%) or had multiple resistance to 2–6 anti-TB agents. Resistance to isoniazid was caused by mutations in the katG gene. Based on the literature analysis and our own observations, we emphasize the importance of developing simple molecular drug susceptibility tests capable of detecting simultaneous resistance to rifampicin and isoniazid and the necessity of their translation into clinical practice.

Treatment of Isoniazid-Resistant Pulmonary Tuberculosis

Tuberculosis (TB) remains a threat to public health and is the leading cause of death globally. Isoniazid (INH) is an important first-line agent for the treatment of TB considering its early bactericidal activity. Resistance to INH is now the most common type of resistance. Resistance to INH reduces the probability of treatment success and increases the risk of acquiring resistance to other first-line drugs such as rifampicin (RIF), thereby increasing the risk of multidrug-resistant-TB. Studies in the 1970s and 1980s showed high success rates for INH-resistant TB cases receiving regimens comprised of first-line drugs. However, recent data have indicated that INH-resistant TB patients treated with only first-line drugs have poor outcomes. Fortunately, based on recent systematic meta-analyses, the World Health Organization published consolidated guidelines on drug-resistant TB in 2019. Their key recommendations are treatment with RIF-ethambutol (EMB)-pyrazinamide (PZA)-levofloxacin (LFX) for 6 months and no addition of injectable agents to the treatment regimen. The guidelines also emphasize the importance of excluding resistance to RIF before starting RIF-EMB-PZA-LFX regimen. Additionally, when the diagnosis of INH-resistant TB is confirmed long after starting the first-line TB treatment, the clinician must decide whether to start a 6-month course of RIF-EMB-PZA-LFX based on the patient's condition. However, these recommendations are based on observational studies, not randomized controlled trials, and are thus conditional and based on low certainty of the effect estimates. Therefore, further work is needed to optimize the treatment of INH-resistant TB.

Evolving rifampicin and isoniazid mono-resistance in a high multidrug-resistant and extensively drug-resistant tuberculosis region: a retrospective data analysis

OBJECTIVES

South Africa ranks among the highest drug-resistant tuberculosis (DR-TB) burdened countries in the world. This study assessed the changes in resistance levels in culture confirmed Mycobacterium tuberculosis (MTB) in the highest burdened province of South Africa during a period where major changes in diagnostic algorithm were implemented.

SETTING

This study was conducted at the central academic laboratory of the KwaZulu-Natal province of South Africa.

PARTICIPANTS

We analysed data for all MTB cultures performed in the KwaZulu-Natal province between 2011 and 2014. The data were collected from the laboratory information system.

RESULTS

Out of 88 559 drug susceptibility results analysed, 18 352 (20.7%) were resistant to rifampicin (RIF) and 19 190 (21.7%) showed resistance to isoniazid (INH). The proportion of rifampicin resistant cases that were mono-resistant increased from 15.3% in 2011 to 21.4% in 2014 while INH mono-resistance (IMR) showed a range between 13.8% and 21.1%. The multidrug-resistant tuberculosis (MDR-TB) rates increased from 18.8% to 23.9% and the proportion of MDR-TB cases that had extensively drug-resistant tuberculosis remained between 10.2% and 11.1%. Most drug resistance was found in females between the ages of 15 and 44 years and the northern districts bordering high MDR-TB regions had the highest MDR-TB rates.

CONCLUSION

Our findings show increasing RIF mono-resistance (RMR) and a substantial amount of IMR. This highlights a need for an initial test that detects resistance to both these drugs so as to avoid using RIF monotherapy during continuous phase of treatment in patients with IMR. Furthermore, addition of INH will benefit patients with RMR. Although DR-TB is widespread, HIV and migration influence its distribution; therefore, TB control strategies should include interventions that target these aspects.

Phenotypic isoniazid resistance and associated mutations in pediatric tuberculosis

BACKGROUND AND OBJECTIVES

Tuberculosis (TB) remains one of the most challenging global health problems as resistance to first-line antimycobacterial drugs continues to rise in many countries worldwide. Isoniazid-resistant TB without MDR-TB poses a serious threat to the management and control of TB across the world. The aim of this study was to investigate the extent of katG315 and inhA-15 mutations in Mycobacterium tuberculosis strains isolated from pediatric TB patients from a tertiary care hospital.

MATERIAL AND METHODS

A total of 51 pulmonary and extra pulmonary specimens were collected from clinically suspected pediatric TB cases, who were microbiologically confirmed. Resistance to INH was detected by 1% proportion method. katG315 and inhA-15 genes were amplified by PCR and detection of mutations in katG315 and inhA-15 genes was done by sequencing.

RESULT

A sample size of only 51 could be achieved due to short duration of the study. 36/51 (70.6%) culture isolates were obtained and put for drug susceptibility test, 5(13.89%) were resistant for isoniazid. M. tuberculosis DNA was found in fifty samples. Mutations in either katG315 or inhA-15 genes were found in 7/50 (14%) samples. Six of seven (85.7%) had mutation in katG315 gene and 1/7 (14.2%) had mutation in inhA-15 gene.

CONCLUSION

INH resistance not only reduces the probability of treatment success, but may also facilitate the spread of MDR-TB and reduce the effectiveness of INH preventive therapy (IPT) therefore quantification of the magnitude of INH resistant TB and variation in frequency of isoniazid resistance associated mutations is important.

Timing of treatment interruption among latently infected tuberculosis cases treated with a nine-month course of daily isoniazid: findings from a time to event analysis

Background

Treatment of latent tuberculosis infection (LTBI) in high-risk groups is an effective strategy for TB control and elimination in low incidence settings. A nine-month course of daily isoniazid (INH) has been the longest prescribed therapy; however, completion rates are suboptimal. We need data to guide TB program outreach efforts to optimize LTBI treatment completion rates.

Methods

We pooled seven (2009–2015) years of LTBI treatment outcome data. We computed the probability of INH treatment disruption over time by patient demographic and clinical risk factors. We used log-rank tests and Cox proportional hazards models to assess the risk factors for treatment disruption.

Results

We analyzed data from 12,495 persons with complete data on INH treatment initiation. Pediatric cases (0–17 years), recent contacts of active TB patients, and non-U.S.-born adults living in the United States ≤5 years represented 25.2, 13.0, and 59.2% of the study population, respectively. Overall, 48.4% failed to complete therapy. The median treatment duration was 306 days (95% CI: 297, 315). A significant drop in adherence could be observed around day 30 of treatment initiation. Indeed, by day 30 of treatment, 17.0% (95% CI: 16.4, 17.7) of patients had defaulted on therapy. Pediatric patients (HR = 0.83, 95% CI: 0.78, 0.89), recent contacts (HR = 0.74, 95% CI: 0.68, 0.81), patients with diabetes (HR = 0.77, 95% CI: 0.60, 0.98), and patients with HIV (HR = 0.39, 95% CI: 0.30, 0.51) had a lower risk of treatment default. However, black patients (HR = 1.57, 95% CI: 1.44, 1.70), Hispanic patients (HR = 1.54, 95% CI: 1.43, 1.66), and non-U.S.-born persons living in the United States ≤5 years (HR = 1.25, 95% CI: 1.18, 1.32) were significantly more likely to default on therapy.

Conclusions

In this analysis of INH treatment outcome, we see high levels of treatment discontinuation. On average, patients defaulted on their prescribed nine-month daily INH therapy within 30 days of initiating treatment, and those at increased risk of progression to active disease were most likely to do so. We highlight the need to introduce patient-centered programs to increase treatment adherence in this population.

Electronic supplementary material

The online version of this article (10.1186/s12889-019-7524-4) contains supplementary material, which is available to authorized users.

Factors associated with isoniazid resistant tuberculosis among human immunodeficiency virus positive patients in Swaziland: a case-control study

Background

Isoniazid resistant tuberculosis is the most prevalent type of resistance in Swaziland and over two-thirds of the isoniazid resistant tuberculosis patients are tuberculosis and human immunodeficiency virus co-infected. The study aimed to determine risk factors associated with isoniazid resistant tuberculosis among human immunodeficiency virus positive patients in Swaziland.

Methods

This was a case-control study conducted in nine healthcare facilities across Swaziland. Cases were patients with isoniazid resistant tuberculosis (including 78 patients with isoniazid mono-resistant tuberculosis, 42 with polydrug-resistant tuberculosis, and 77 with multidrug-resistant tuberculosis). Controls were presumed drug-susceptible tuberculosis patients (n = 203). Multinomial logistic regression was used to determine related factors.

Results

The median time lag from diagnosis to tuberculosis treatment initiation was 50 days for isoniazid mono or poly drug-resistant tuberculosis, 17 days for multidrug-resistant tuberculosis compared to 1 day for drug-susceptible tuberculosis patients. History of previous tuberculosis treatment was positively associated with either isoniazid mono or poly drug-resistant tuberculosis (OR = 7.91, 95% CI: 4.14–15.11) and multidrug-resistant tuberculosis (OR = 12.20, 95% CI: 6.07–24.54). Isoniazid mono or poly resistant tuberculosis patients were more likely to be from rural areas (OR = 2.05, 95% CI: 1.23–3.32) and current heavy alcohol drinkers compared to the drug-susceptible tuberculosis group. Multi drug-resistant tuberculosis patients were more likely to be non-adherent to tuberculosis treatment compared to drug-susceptible tuberculosis group (OR = 3.01, 95% CI: 1.56–5.82).

Conclusion

To prevent and control isoniazid resistant tuberculosis among HIV-positive patients in Swaziland, the tuberculosis program should strengthen the use of rapid diagnostic tests, detect resistance early, promptly initiate supervised tuberculosis treatment and decentralize quality tuberculosis services to the rural areas. Adherence to tuberculosis treatment should be improved.

Electronic supplementary material

The online version of this article (10.1186/s12879-019-4384-6) contains supplementary material, which is available to authorized users.

Change in prevalence and molecular characteristics of isoniazid-resistant tuberculosis over a 10-year period in China

BACKGROUND

Isoniazid (INH) represents the cornerstone for the treatment of cases infected with Mycobacterium tuberculosis (MTB) strains. Several molecular mechanisms have been shown to be the major causes for INH resistance, while the dynamic change of mutations conferring INH resistance among MTB strains during the past decade is still unknown in China.

METHODS

In this study, we carried out a comparative analysis of the INH minimal inhibitory concentration (MIC) distribution, and investigate the dynamic change of molecular characteristics among INH-resistant MTB strains between 2005 and 2015.

RESULTS

The proportion of INH resistance (39.0%, 105/269) in 2015 was significantly higher than in 2005 (30.0%, 82/273; P = 0.03). Among 269 isolates collected in 2015, 76 (28.3%, 76/269) exhibited high-level INH-resistance (MIC≥32 mg/L), which was significantly higher than that in 2005 (20.5%, 56/273, P = 0.04). In addition, a significantly higher percentage of INH-resistant isolates carried inhA promoter mutations in 2015 (26.7%) versus that in 2005 (14.6%, P = 0.04), while no significant difference was observed in the rates of isolates containing katG mutations between 2005 (76.8%) and 2015 (70.5%, P = 0.33). Notably, the proportion of MTB isolates with inhA mutations (26.7%, 28/105) for patients who had previous exposure to protionamide (PTH) was higher than that for patients who had no previous exposure to PTH (21.4%, 6/28).

CONCLUSIONS

In conclusion, our results demonstrated that the proportion of INH-resistant MTB isolates significantly increased during the last decade, which was mainly attributed to an increase of high-level INH-resistant MTB. In addition, prior exposure to PTH may be associated with the increased frequency of INH-resistant tuberculosis strains with inhA mutations in China.

Isoniazid mono-resistant tuberculosis: Time to take it seriously

BACKGROUND/AIMS

In drug resistant tuberculosis (DRTB) suspects, rifampicin resistance has always been prioritized, hence Cartridge Based Nucleic Acid Amplification Test (CBNAAT) is recommended under Revised National Tuberculosis Control Programme (RNTCP), India. However, since it doesn't detect isoniazid resistance, rifampicin sensitive patients with unknown isoniazid status may be erroneously treated as drug sensitive TB, leading to poor treatment outcomes and emergence of multidrug resistant (MDR) TB. Hence isoniazid mono-resistance should be specifically looked for and treated as per recommendations. The objective of the present study, almost the first of its kind in India, was to evaluate the burden of isoniazid mono-resistance amongst patients diagnosed with DRTB and to study the association of different patient and disease related factors with treatment outcomes under the treatment regimen specific for isoniazid mono-resistance, started from January 1, 2017 in our state, under RNTCP.

METHODS

It was a retrospective study which scrutinized medical records of 52 isoniazid mono-resistant TB patients started on treatment under RNTCP between January 1 to December 31, 2017. Necessary information on possible patient and disease related predicting factors like gender, age, type of mutation (katG/inhA), weight band (26-45 kg/46-70 kg), total serum protein/albumin levels, previous history of anti-tubercular treatment (ATT), history of smoking, HIV status, presence of diabetes mellitus (DM), presence of anemia, occurrence of adverse drug reactions (ADR) during treatment and duration of intensive phase (IP), was retrieved. These factors were analyzed for their possible association with treatment outcomes.

RESULTS

Out of 103 DRTB patients enrolled, 50.5% (52/103) patients were diagnosed with isoniazid mono-resistance. 50/103 were MDR-TB and 1/103 were extensively-drug resistant TB (XDR-TB). Further analysis of these 52 isoniazid mono-resistant patients revealed:35 (67.3%) were males and 17 (32.7%) females. 27 (51.9%) patients were <30 years, 25 (48.1%) being ≥30 years of age. All patients were negative for HIV. 34/52 (65.4%) patients were declared cured, 15/52 were lost to follow up (LTFU) and 3/52 died (1 male, 2 females). Excluding these 3 patients who died, cure rates were significantly better in females (14/15 = 93.3%), with only 1/15 LTFU, than males (20/34 = 58.8% cure, 14/34 = 41.2% LTFU), (p = 0.019). Patients who were <30 years of age had significantly better cure rates (21/25 = 84%) with lesser LTFU's (4/25 = 16%), than those ≥30years of age (13/24 = 54.2% cure, 11/24 = 45.8% LTFU), (p = 0.032). Review of previous history of ATT revealed that 33 patients had primary isoniazid mono-resistance, 4 patients had previous history of being LTFU, 9 had recurrent TB and 3 were labeled as failure. Cure rates were significantly better in primary isoniazid mono-resistant patients (26/33 = 78.8%), than those with previous history of being LTFU(0/4), (p = 0.04). Type of mutation, weight band, total serum protein/albumin, history of smoking, presence of DM, presence of anemia, occurrence of ADR and duration of IP did not affect treatment outcomes.

CONCLUSION

Isoniazid mono-resistance formed a major chunk of DRTB, with majority of the patients detected with primary mono-resistance. Strategically framed treatment regimens for isoniazid mono-resistance under RNTCP in India are effective in a wide range of population. Still, there are high chances of LTFU/default, which needs to be addressed on priority. Male gender, age ≥30 years and being LTFU in the past are associated with poorer cure rates, hence should be paid special attention.

Isoniazid Monoresistance and Rate of Culture Conversion among Patients in the State of Georgia with Confirmed Tuberculosis, 2009-2014

RATIONALE

Isoniazid-monoresistant tuberculosis (INH-monoresistant TB) is the most common drug-resistant TB type in the United States; however, its impact on TB treatment outcomes is not clear.

OBJECTIVES

This study aims to understand 1) factors associated with INH-monoresistant TB and 2) the association between INH monoresistance and response to TB treatment.

METHODS

We studied all patients with TB (age, ≥15 yr) reported to the Georgia State Electronic Notifiable Disease Surveillance System (SENDSS) from 2009 to 2014. INH-monoresistant TB was defined as a Mycobacterium tuberculosis isolate resistant to isoniazid only. Time to sputum culture conversion was defined as the time (measured in days) from TB treatment initiation to the date of the first consistently negative culture result reported to the SENDSS. Logistic regression and Cox proportional hazard models were used to estimate the odds and hazard rate of sputum culture conversion, all-cause mortality, and poor TB outcome among patients with INH-monoresistant TB.

RESULTS

Among 1,141 culture-confirmed patients with available drug susceptibility testing results, 998 (87.5%) were susceptible to TB first-line drugs, and 143 (12.5%) were patients with INH-monoresistant TB. In multivariable analysis, male sex (adjusted odds ratio [aOR], 1.62; 95% confidence interval [CI], 1.01-2.67) and homelessness (aOR, 5.55; 95% CI, 3.38-9.17) were associated with higher odds of INH-monoresistant TB. In the same multivariable model, older age (≥65 yr old) (aOR, 0.21; 95% CI, 0.07-0.55) and miliary disease (aOR, 0.19; 95% CI, 0.01-0.96) were associated with lower odds of INH-monoresistant TB. Among 1,116 patients with pulmonary TB, the median time to sputum culture conversion was 30 days (interquartile range, 13-58). The rate of culture conversion was similar among patients with and without INH monoresistance (adjusted cause-specific hazard ratio, 1.15; 95% CI, 0.95-1.40). INH-monoresistant TB was not significantly associated with poor TB treatment outcomes (aOR, 1.61; 95% CI, 0.67-3.70) or mortality during TB treatment (aOR, 1.72; 95% CI, 0.58-4.94).

CONCLUSIONS

Our findings suggest that compared with drug-susceptible TB, patients in Georgia with INH-monoresistant TB have a similar response to TB treatment including culture conversion rate, final TB treatment outcome, and all-cause mortality.

Evaluation of two tuberculosis PCR assays for routine use in a clinical setting of low population and low tuberculosis prevalence

Today, there are numerous different molecular diagnostic assays for the detection of tuberculosis (TB), allowing the optimization of rapid detection of TB according to the clinical need. In this study, two high-throughput TB PCR assays with combined antimicrobial resistance detection, Anyplex™ II MTB/MDR (Seegene) and RealTime MTB + RealTime MTB RIF/INH Resistance (Abbott Molecular), were evaluated for routine use in a clinical setting of low population and low TB prevalence in Finland. The RealTime MTB assay was 100% concordant (22/22 positive, n = 169) with the reference methods (culture and Xpert MTB/RIF PCR assay, Cepheid). However, with a limitation of four separate PCR cycles per kit, the routine use in a low TB-prevalence setting would easily lead to wasting most of the RIF/INH Resistance reagents. The Anyplex™ II MTB/MDR assay usability was more adaptive to suit the clinical setting but the assay sensitivity was considerably lower (86%, 19/22 positive, n = 76) being closer to the sensitivity of smear microscopy. The findings of this study suggest that the evaluated high-throughput MTB/MDR assays are evidently suboptimal for routine use in a low population, low TB-prevalence setting. In addition, neither of the two assays covers non-tuberculous mycobacteria and could therefore not fully replace acid-fast staining as the initial screening method.

Comparison of different treatments for isoniazid-resistant tuberculosis: an individual patient data meta-analysis

BACKGROUND

Isoniazid-resistant, rifampicin-susceptible (INH-R) tuberculosis is the most common form of drug resistance, and is associated with failure, relapse, and acquired rifampicin resistance if treated with first-line anti-tuberculosis drugs. The aim of the study was to compare success, mortality, and acquired rifampicin resistance in patients with INH-R pulmonary tuberculosis given different durations of rifampicin, ethambutol, and pyrazinamide (REZ); a fluoroquinolone plus 6 months or more of REZ; and streptomycin plus a core regimen of REZ.

METHODS

Studies with regimens and outcomes known for individual patients with INH-R tuberculosis were eligible, irrespective of the number of patients if randomised trials, or with at least 20 participants if a cohort study. Studies were identified from two relevant systematic reviews, an updated search of one of the systematic reviews (for papers published between April 1, 2015, and Feb 10, 2016), and personal communications. Individual patient data were obtained from authors of eligible studies. The individual patient data meta-analysis was performed with propensity score matched logistic regression to estimate adjusted odds ratios (aOR) and risk differences of treatment success (cure or treatment completion), death during treatment, and acquired rifampicin resistance. Outcomes were measured across different treatment regimens to assess the effects of: different durations of REZ (≤6 months vs >6 months); addition of a fluoroquinolone to REZ (fluoroquinolone plus 6 months or more of REZ vs 6 months or more of REZ); and addition of streptomycin to REZ (streptomycin plus 6 months of rifampicin and ethambutol and 1-3 months of pyrazinamide vs 6 months or more of REZ). The overall quality of the evidence was assessed using GRADE methodology.

FINDINGS

Individual patient data were requested for 57 cohort studies and 17 randomised trials including 8089 patients with INH-R tuberculosis. We received 33 datasets with 6424 patients, of which 3923 patients in 23 studies received regimens related to the study objectives. Compared with a daily regimen of 6 months of (H)REZ (REZ with or without isoniazid), extending the duration to 8-9 months had similar outcomes; as such, 6 months or more of (H)REZ was used for subsequent comparisons. Addition of a fluoroquinolone to 6 months or more of (H)REZ was associated with significantly greater treatment success (aOR 2·8, 95% CI 1·1-7·3), but no significant effect on mortality (aOR 0·7, 0·4-1·1) or acquired rifampicin resistance (aOR 0·1, 0·0-1·2). Compared with 6 months or more of (H)REZ, the standardised retreatment regimen (2 months of streptomycin, 3 months of pyrazinamide, and 8 months of isoniazid, rifampicin, and ethambutol) was associated with significantly worse treatment success (aOR 0·4, 0·2-0·7). The quality of the evidence was very low for all outcomes and treatment regimens assessed, owing to the observational nature of most of the data, the diverse settings, and the imprecision of estimates.

INTERPRETATION

In patients with INH-R tuberculosis, compared with treatment with at least 6 months of daily REZ, addition of a fluoroquinolone was associated with better treatment success, whereas addition of streptomycin was associated with less treatment success; however, the quality of the evidence was very low. These results support the conduct of randomised trials to identify the optimum regimen for this important and common form of drug-resistant tuberculosis.

FUNDING

World Health Organization and Canadian Institutes of Health Research.

Emergence and selection of isoniazid and rifampin resistance in tuberculosis granulomas

Drug resistant tuberculosis is increasing world-wide. Resistance against isoniazid (INH), rifampicin (RIF), or both (multi-drug resistant TB, MDR-TB) is of particular concern, since INH and RIF form part of the standard regimen for TB disease. While it is known that suboptimal treatment can lead to resistance, it remains unclear how host immune responses and antibiotic dynamics within granulomas (sites of infection) affect emergence and selection of drug-resistant bacteria. We take a systems pharmacology approach to explore resistance dynamics within granulomas. We integrate spatio-temporal host immunity, INH and RIF dynamics, and bacterial dynamics (including fitness costs and compensatory mutations) in a computational framework. We simulate resistance emergence in the absence of treatment, as well as resistance selection during INH and/or RIF treatment. There are four main findings. First, in the absence of treatment, the percentage of granulomas containing resistant bacteria mirrors the non-monotonic bacterial dynamics within granulomas. Second, drug-resistant bacteria are less frequently found in non-replicating states in caseum, compared to drug-sensitive bacteria. Third, due to a steeper dose response curve and faster plasma clearance of INH compared to RIF, INH-resistant bacteria have a stronger influence on treatment outcomes than RIF-resistant bacteria. Finally, under combination therapy with INH and RIF, few MDR bacteria are able to significantly affect treatment outcomes. Overall, our approach allows drug-specific prediction of drug resistance emergence and selection in the complex granuloma context. Since our predictions are based on pre-clinical data, our approach can be implemented relatively early in the treatment development process, thereby enabling pro-active rather than reactive responses to emerging drug resistance for new drugs. Furthermore, this quantitative and drug-specific approach can help identify drug-specific properties that influence resistance and use this information to design treatment regimens that minimize resistance selection and expand the useful life-span of new antibiotics.

Prevalence of drug-resistant tuberculosis and imputed burden in South Africa: a national and sub-national cross-sectional survey

BACKGROUND

Globally, per-capita, South Africa reports a disproportionately high number of cases of multidrug-resistant (MDR) tuberculosis and extensively drug-resistant (XDR) tuberculosis. We sought to estimate the prevalence of resistance to tuberculosis drugs in newly diagnosed and retreated patients with tuberculosis provincially and nationally, and compared these with the 2001-02 estimates.

METHODS

A cross-sectional survey was done between June 15, 2012-June 14, 2014, using population proportionate randomised cluster sampling in the nine provinces in South Africa. 343 clusters were included, ranging between 31 and 48 per province. A patient was eligible for inclusion in the survey if he or she presented as a presumptive case during the intake period at a drug resistance survey enrolling facility. Consenting participants (≥18 years old) completed a questionnaire and had a sputum sample tested for resistance to first-line and second-line drugs. Analysis was by logistic regression with robust SEs, inverse probability weighted against routine data, and estimates were derived using a random effects model.

FINDINGS

101 422 participants were tested in 2012-14. Nationally, the prevalence of MDR tuberculosis was 2·1% (95% CI 1·5-2·7) among new tuberculosis cases and 4·6% (3·2-6·0) among retreatment cases. The provincial point prevalence of MDR tuberculosis ranged between 1·6% (95% CI 0·9-2·9) and 5·1% (3·7-7·0). Overall, the prevalence of rifampicin-resistant tuberculosis (4·6%, 95% CI 3·5-5·7) was higher than the prevalence of MDR tuberculosis (2·8%, 2·0-3·6; p=0·01). Comparing the current survey with the previous (2001-02) survey, the overall MDR tuberculosis prevalence was 2·8% versus 2·9% and prevalance of rifampicin-resistant tuberculosis was 3·4% versus 1·8%, respectively. The prevalence of isoniazid mono-resistant tuberculosis was above 5% in all provinces. The prevalence of ethionamide and pyrazinamide resistance among MDR tuberculosis cases was 44·7% (95% CI 25·9-63·6) and 59·1% (49·0-69·1), respectively. The prevalence of XDR tuberculosis was 4·9% (95% CI 1·0-8·8). Nationally, the estimated numbers of cases of rifampicin-resistant tuberculosis, MDR tuberculosis, and isoniazid mono-resistant tuberculosis for 2014 were 13 551, 8249, and 17 970, respectively.

INTERPRETATION

The overall prevalence of MDR tuberculosis in South Africa in 2012-14 was similar to that in 2001-02; however, prevalence of rifampicin-resistant tuberculosis almost doubled among new cases. Furthermore, the high prevalence of isoniazid mono-resistant tuberculosis, not routinely screened for, and resistance to second-line drugs has implications for empirical management.

FUNDING

President's Emergency Plan for AIDS Relief through the Centers for Disease Control and Prevention under the terms of 1U19GH000571.

Isoniazid-monoresistant tuberculosis is associated with poor treatment outcomes in Durban, South Africa

SETTING

A large tuberculosis (TB) clinic in Durban, South Africa.

OBJECTIVE

To determine the association between isoniazid (INH) monoresistant TB and treatment outcomes.

DESIGN

We performed a retrospective longitudinal study of patients seen from 2000 to 2012 to compare episodes of INH-monoresistant TB with those of drug-susceptible TB using logistic regression with robust standard errors. INH-monoresistant TB was treated with modified regimens.

RESULTS

Among 18 058 TB patients, there were 19 979 TB episodes for which drug susceptibility testing was performed. Of these, 557 were INH-monoresistant and 16 311 were drug-susceptible. Loss to follow-up, transfer, and human immunodeficiency virus (HIV) co-infection (41% had known HIV status) were similar between groups. INH-monoresistant episodes were more likely to result in treatment failure (4.1% vs. 0.6%, P < 0.001) and death (3.2% vs. 1.8%, P = 0.01) than drug-susceptible episodes. After adjustment for age, sex, race, retreatment status, and disease site, INH-monoresistant episodes were more likely to have resulted in treatment failure (OR 6.84, 95%CI 4.29-10.89, P < 0.001) and death (OR 1.81, 95%CI 1.11-2.95, P = 0.02).

CONCLUSION

INH monoresistance was associated with worse clinical outcomes than drug-susceptible TB. Our findings support the need for rapid diagnostic tests for INH resistance and improved treatment regimens for INH-monoresistant TB.

Isoniazid-resistant tuberculosis: a cause for concern?

The drug isoniazid (INH) is a key component of global tuberculosis (TB) control programmes. It is estimated, however, that 16.1% of TB disease cases in the former Soviet Union countries and 7.5% of cases outside of these settings have non-multidrug-resistant (MDR) INH resistance. Resistance has been linked to poorer treatment outcomes, post-treatment relapse and death, at least for specific sites of disease. Multiple genetic loci are associated with phenotypic resistance; however, the relationship between genotype and phenotype is complex, and restricts the use of rapid sequencing techniques as part of the diagnostic process to determine the most appropriate treatment regimens for patients. The burden of resistance also influences the usefulness of INH preventive therapy. Despite seven decades of INH use, our knowledge in key areas such as the epidemiology of resistant strains, their clinical consequences, whether tailored treatment regimens are required and the role of INH resistance in fuelling the MDR-TB epidemic is limited. The importance of non-MDR INH resistance needs to be re-evaluated both globally and by national TB control programmes.

Time to Sputum Culture Conversion and Treatment Outcomes Among Patients with Isoniazid-Resistant Tuberculosis in Atlanta, Georgia

BACKGROUND

Although isoniazid-resistant tuberculosis is more common than multidrug-resistant tuberculosis, it has been much less studied. We examined the impact of isoniazid resistance and treatment regimen, including use of a fluoroquinolone, on clinical outcomes.

METHODS

A retrospective cohort study among patients with sputum culture-positive tuberculosis was performed. Early fluoroquinolone (FQ) use was defined as receiving ≥5 doses during the first month of treatment. The primary outcome was time to sputum culture conversion (tSCC). A multivariate proportional hazards model was used to determine the association of isoniazid resistance with tSCC.

RESULTS

Among 236 patients with pulmonary tuberculosis, 59 (25%) had isoniazid resistance. The median tSCC was similar for isoniazid-resistant and -susceptible cases (35 vs 29 days; P = .39), and isoniazid resistance was not associated with tSCC in multivariate analysis (adjusted hazard ratio = 0.83; 95% confidence interval [CI], .59-1.17). Early FQ use was higher in isoniazid-resistant than -susceptible cases (20% vs 10%; P = .05); however, it was not significantly associated with tSCC in univariate analysis (hazard ratio = 1.48; 95% CI, .95-2.28). Patients with isoniazid-resistant tuberculosis were treated with regimens containing rifampin, pyrazinamide, and ethambutol +/- a FQ for a median of 9.7 months. Overall, 191 (83%) patients were cured. There was no difference in initial treatment outcomes; however, all cases of acquired-drug resistance (n = 1) and recurrence (n = 3) occurred among patients with isoniazid-resistant tuberculosis.

CONCLUSIONS

There was no significant association with isoniazid resistance and tSCC or initial treatment outcomes. Although patients with isoniazid-resistant tuberculosis had a high cure rate, the cases of recurrence and acquired drug resistance are concerning and highlight the need for longer-term follow-up studies.

Treatment outcomes for isoniazid-resistant tuberculosis under program conditions in British Columbia, Canada

Background

Every year, over 1 million people develop isoniazid (INH) resistant tuberculosis (TB). Yet, the optimal treatment regimen remains unclear. Given increasing prevalence, the clinical efficacy of regimens used by physicians is of interest. This study aims to examine treatment outcomes of INH resistant TB patients, treated under programmatic conditions in British Columbia, Canada.

Methods

Medical charts were retrospectively reviewed for cases of culture-confirmed INH mono-resistant TB reported to the BC Centre for Disease Control (BCCDC) from 2002 to 2014. Treatment regimens, patient and strain characteristics, and clinical outcomes were analysed.

Results

One hundred sixty five cases of INH mono-resistant TB were included in analysis and over 30 different treatment regimens were prescribed. Median treatment duration was 10.5 months (IQR 9–12 months) and treatment was extended beyond 12 months for 26 patients (15.8%). Fifty six patients (22.6%) experienced an adverse event that resulted in a drug regimen modification. Overall, 140 patients (84.8%) had a successful treatment outcome while 12 (7.2%) had an unsuccessful treatment outcome of failure (n = 2; 1.2%), relapse (n = 4; 2.4%) or all cause mortality (n = 6; 3.6%).

Conclusion

Our treatment outcomes, while consistent with findings reported from other studies in high resource settings, raise concerns about current recommendations for INH resistant TB treatment. Only a small proportion of patients completed the recommended treatment regimens. High quality studies to confirm the effectiveness of standardized regimens are urgently needed, with special consideration given to trials utilizing fluoroquinolones.

Tuberculosis of the Knee: A Case Report and Literature Review

Tuberculosis (TB) is currently in resurgence due to immigration from endemic areas. Skeletal TB frequently mimics more common etiologies and can be difficult to diagnose. A case of TB knee arthritis in a young woman with painful and swelling knee is reported here. Arthrotomy was performed and inflamed synovial tissue was found, with multiple rice bodies in the eroded lateral femoral condyle. The patient was treated with an antituberculosis polytherapy and at 1-year follow-up, she reported relief from pain and swelling. We believe that all surgeons assessing patients from TB endemic regions have to adopt an updated approach to TB treatment. Thus, a literature review is also reported here on the current strategies used in different knee TB cases.

Genomic analysis of globally diverse Mycobacterium tuberculosis strains provides insights into the emergence and spread of multidrug resistance

Multidrug-resistant tuberculosis (MDR-TB), caused by drug resistant strains of Mycobacterium tuberculosis, is an increasingly serious problem worldwide. In this study, we examined a dataset of 5,310 M. tuberculosis whole genome sequences from five continents. Despite great diversity with respect to geographic point of isolation, genetic background and drug resistance, patterns of drug resistance emergence were conserved globally. We have identified harbinger mutations that often precede MDR. In particular, the katG S315T mutation, conferring resistance to isoniazid, overwhelmingly arose before rifampicin resistance across all lineages, geographic regions, and time periods. Molecular diagnostics that include markers for rifampicin resistance alone will be insufficient to identify pre-MDR strains. Incorporating knowledge of pre-MDR polymorphisms, particularly katG S315, into molecular diagnostics will enable targeted treatment of patients with pre-MDR-TB to prevent further development of MDR-TB.

Redefining MTBDRplus test results: what do indeterminate results actually mean?

BACKGROUND

Although line-probe assays (LPAs) are promising, little research has been conducted to elucidate the true nature of indeterminate LPA results or assess the ability of these assays to perform on a wide range of clinical samples.

OBJECTIVE

To evaluate the performance of the commercially available GenoType(®) MTBDRplus LPA against conventional BACTEC™ MGIT™ 960 culture and drug susceptibility testing (DST) among 308 pulmonary tuberculosis (PTB) and 32 extra-pulmonary TB samples.

RESULTS

Invalid LPA results (defined as those with a missing Mycobacterium tuberculosis identification band) were obtained for 18 PTB samples, which were excluded from further analysis. The sensitivity and specificity of the MTBDRplus assay for multidrug-resistant TB, based upon the results obtained for the remaining 322 samples, was respectively 95.2% and 95.1%. Of 290 PTB samples, 40 (13.7%) were indeterminate on LPA (defined as the absence of both wild-type and corresponding mutation bands) for isoniazid (INH) and/or rifampicin (RMP), and were further evaluated by pyrosequencing (PSQ). Contrary to standard LPA interpretation, INH and RMP susceptibility were confirmed by both DST and PSQ in respectively 7.5% (3/40) and 27.5% (11/40) of indeterminate samples.

CONCLUSION

PSQ was found to be a valuable and rapid technique to resolve discrepancies in LPA test results that were not interpretable.

Epidemiology of Drug-resistant Tuberculosis in a Tertiary Care Center in Oman, 2006-2015

OBJECTIVES

The aim of this study was to estimate the prevalence and identify the risk factors for the development of drug-resistant Mycobacterium tuberculosis infection in a tertiary care center in Oman.

METHODS

We performed a cross-sectional review of culture-confirmed tuberculosis (TB) cases diagnosed at Sultan Qaboos University Hospital between August 2006 and March 2015. We compared drug-resistant TB cases with drug-sensitive cases to identify predictors of drug-resistant TB using univariate and multivariate logistic regression analysis.

RESULTS

Of the 260 TB cases reviewed, 73.1% were confirmed by culture. The proportion of multi-drug resistant TB was 1.8%. TB isolates resistant to any of the first-line TB drugs comprised (7.5%) of cases. Pyrazinamide monoresistance was the most frequently reported drug monoresistant pattern (3.5%). Previous treatment for TB (odds ratio (OR) 14.81; 95% CI 3.09-70.98, p < 0.001), female gender (OR 3.85; 95% Cl 1.07-13.90, p < 0.039), and younger age (OR 6.80; 95% Cl 1.61-28.75, p < 0.009) were found to be risk factors for development of first-line antituberculosis drug-resistant TB in multivariate analysis.

CONCLUSIONS

Our results show that the rate of drug-resistant TB in our population is a public health issue of great concern. Previous treatment with antituberculosis drugs, female gender, and younger age are risk factors for the development of drug-resistant TB. These findings are useful adjuvants to guide clinicians and public health professionals in the early detection and appropriate treatment of cases of drug-resistant TB.

Isoniazid Mono-Resistant Tuberculosis: Impact on Treatment Outcome and Survival of Pulmonary Tuberculosis Patients in Southern Mexico 1995-2010

Background

Isoniazid mono-resistance (IMR) is the most common form of mono-resistance; its world prevalence is estimated to range between 0.0 to 9.5% globally. There is no consensus on how these patients should be treated.

Objective

To describe the impact of IMR tuberculosis (TB) on treatment outcome and survival among pulmonary TB patients treated under programmatic conditions in Orizaba, Veracruz, Mexico.

Materials and Methods

We conducted a prospective cohort study of pulmonary TB patients in Southern Mexico. From 1995 to 2010 patients with acid-fast bacilli or culture proven Mycobacterium tuberculosis in sputum samples underwent epidemiological, clinical and microbiological evaluation. We included patients who harbored isoniazid mono-resistant (IMR) strains and patients with strains susceptible to isoniazid, rifampicin, ethambutol and streptomycin. All patients were treated following Mexican TB Program guidelines. We performed annual follow-up to ascertain treatment outcome, recurrence, relapse and mortality.

Results

Between 1995 and 2010 1,243 patients with pulmonary TB were recruited; 902/1,243 (72.57%) had drug susceptibility testing; 716 (79.38%) harbored pan-susceptible and 88 (9.75%) IMR strains. Having any contact with a person with TB (adjusted odds ratio (aOR)) 1.85, 95% Confidence interval (CI) 1.15–2.96) and homelessness (adjusted odds ratio (aOR) 2.76, 95% CI 1.08–6.99) were associated with IMR. IMR patients had a higher probability of failure (adjusted hazard ratio (HR) 12.35, 95% CI 3.38–45.15) and death due to TB among HIV negative patients (aHR 3.30. 95% CI 1.00–10.84). All the models were adjusted for socio-demographic and clinical variables.

Conclusions

The results from our study provide evidence that the standardized treatment schedule with first line drugs in new and previously treated cases with pulmonary TB and IMR produces a high frequency of treatment failure and death due to tuberculosis. We recommend re-evaluating the optimal schedule for patients harboring IMR. It is necessary to strengthen scientific research for the evaluation of alternative treatment schedules in similar settings.

First Evaluation of GenoType MTBDRplus 2.0 Performed Directly on Respiratory Specimens in Central America

The turnaround times for conventional methods used to detect Mycobacterium tuberculosis in sputum samples and to obtain drug susceptibility information are long in many developing countries, including Panama, leading to delays in appropriate treatment initiation and continued transmission in the community. We evaluated the performance of a molecular line probe assay, the Genotype MTBDRplus version 2.0 assay, in detecting M. tuberculosis complex directly in respiratory specimens from smear-positive tuberculosis cases from four different regions in Panama, as well as the most frequent mutations in genes conferring resistance to isoniazid (katG and inhA) and rifampin (rpoB). Our results were confirmed with the nitrate reductase assay and genomic sequencing. M. tuberculosis complex was detected by the Genotype MTBDRplus 2.0 assay with 100% sensitivity and specificity. The sensitivity and specificity for rifampin resistance were 100% and 100%, respectively, and those for isoniazid resistance were 90.7% and 100%. Isoniazid monoresistance was detected in 5.2% of new cases. Genotype MTBDRplus 2.0 is highly accurate in detecting M. tuberculosis complex in respiratory specimens and is able to discriminate isoniazid-monoresistant cases from multidrug-resistant cases within 2 days.

Diagnostic Molecular Mycobacteriology in Regions With Low Tuberculosis Endemicity: Combining Real-time PCR Assays for Detection of Multiple Mycobacterial Pathogens With Line Probe Assays for Identification of Resistance Mutations

Molecular assays have not yet been able to replace time-consuming culture-based methods in clinical mycobacteriology.

Using 6875 clinical samples and a study period of 35 months we evaluated the use of PCR-based assays to establish a diagnostic workflow with a fast time-to-result of 1–2 days, for 1. detection of Mycobacterium tuberculosis complex (MTB), 2. detection and identification of nontuberculous mycobacteria (NTM), and 3. identification of drug susceptible MTB.

MTB molecular-based detection and culture gave concordant results for 97.7% of the specimens. NTM PCR-based detection and culture gave concordant results for 97.0% of the specimens. Defining specimens on the basis of combined laboratory data as true positives or negatives with discrepant results resolved by clinical chart reviews, we calculated sensitivity, specificity, PPV and NPV for PCR-based MTB detection as 84.7%, 100%, 100%, and 98.7%; the corresponding values for culture-based MTB detection were 86.3%, 100%, 100%, and 98.8%. PCR-based detection of NTM had a sensitivity of 84.7% compared to 78.0% of that of culture-based NTM detection. Molecular drug susceptibility testing (DST) by line-probe assay was found to predict phenotypic DST results in MTB with excellent accuracy.

Our findings suggest a diagnostic algorithm to largely replace lengthy culture-based techniques by rapid molecular-based methods.

•

Molecular assays have not yet been able to replace time-consuming culture-based methods in the mycobacteriology laboratory.

•

We have evaluated genetic tests for: i) detection of MTB, ii) detection of NTM, and iii) identification of susceptible MTB.

•

Our findings suggest a diagnostic algorithm to replace lengthy culture-based techniques by rapid molecular-based methods.

There are > 700 reports on molecular detection of tuberculosis in respiratory and non-respiratory specimens. Limited published data exist on molecular tests for detection of nontuberculous mycobacteria (NTM) and tuberculosis drug susceptibility in clinical samples. We demonstrate an excellent accuracy of molecular-based detection of tuberculosis and NTM in conjunction with molecular-based rapid recognition of drug-susceptible and drug-resistant tuberculosis. The diagnostic algorithm developed in this work allows the rapid recognition of clinically relevant mycobacterial infections and tuberculosis drug resistance.

Prevalence, Risk Factors, and Treatment Outcomes of Isoniazid- and Rifampicin-Mono-Resistant Pulmonary Tuberculosis in Lima, Peru

Background

Isoniazid and rifampicin are the two most efficacious first-line agents for tuberculosis (TB) treatment. We assessed the prevalence of isoniazid and rifampicin mono-resistance, associated risk factors, and the association of mono-resistance on treatment outcomes.

Methods

A prospective, observational cohort study enrolled adults with a first episode of smear-positive pulmonary TB from 34 health facilities in a northern district of Lima, Peru, from March 2010 through December 2011. Participants were interviewed and a sputum sample was cultured on Löwenstein-Jensen (LJ) media. Drug susceptibility testing was performed using the proportion method. Medication regimens were documented for each patient. Our primary outcomes were treatment outcome at the end of treatment. The secondary outcome included recurrent episodes among cured patients within two years after completion of the treatment.

Results

Of 1292 patients enrolled, 1039 (80%) were culture-positive. From this subpopulation, isoniazid mono-resistance was present in 85 (8%) patients and rifampicin mono-resistance was present in 24 (2%) patients. In the multivariate logistic regression model, isoniazid mono-resistance was associated with illicit drug use (adjusted odds ratio (aOR) = 2.10; 95% confidence interval (CI): 1.1–4.1), and rifampicin mono-resistance was associated with HIV infection (aOR = 9.43; 95%CI: 1.9–47.8). Isoniazid mono-resistant patients had a higher risk of poor treatment outcomes including treatment failure (2/85, 2%, p-value<0.01) and death (4/85, 5%, p<0.02). Rifampicin mono-resistant patients had a higher risk of death (2/24, 8%, p<0.01).

Conclusion

A high prevalence of isoniazid and rifampicin mono-resistance was found among TB patients in our low HIV burden setting which were similar to regions with high HIV burden. Patients with isoniazid and rifampicin mono-resistance had an increased risk of poor treatment outcomes.

A child with complicated Mycobacterium tuberculosis

Tuberculosis (TB) is one of the leading causes of morbidity and mortality worldwide, with ever increasing resistance to commonly used antituberculous drugs. Drug-resistant TB was recognized shortly after the introduction of an effective therapy in the late 1940s, the use of streptomycin, which was the first widely used antituberculosis drug. Patients who received this drug usually had marked and rapid clinical improvement, but treatment failures were common after the first three months of therapy. Most children are infected by household contacts who have TB, particularly parents or other caretakers. Common symptoms of pulmonary TB in children include cough (chronic, without improvement for more than three weeks), fever (higher than 38 °C for more than two weeks), and weight loss or failure to thrive. Findings on a physical exam may suggest the presence of a lower respiratory infection, whereas the clinical presentation of extra pulmonary TB depends on the site of disease. The most common forms of extra pulmonary disease in children are TB of the lymph nodes and of the central nervous system. The role of inadequate treatment and poor compliance in the emergence of resistance highlights the importance of the DOT (Direct Observation Therapy) method in improving treatment outcomes and to control the spread of resistance.

Treatment Outcomes with Fluoroquinolone-Containing Regimens for Isoniazid-Resistant Pulmonary Tuberculosis

Resistance to isoniazid (INH) is the most common form of drug resistance in pulmonary tuberculosis (TB). Although fluoroquinolones (FQs) are recommended to strengthen treatment regimens for INH-resistant pulmonary TB, few studies have evaluated the clinical efficacy of FQ-containing regimens in patients with INH-resistant pulmonary TB. A retrospective cohort study of 140 patients with INH-resistant pulmonary TB was performed between 2005 and 2012. We evaluated whether FQ-containing regimens yielded improved treatment outcomes for patients with INH-resistant pulmonary TB. Overall, favorable outcomes were achieved in 128 (91.4%) patients. Unfavorable outcomes occurred in 12 patients (8.6%), including 7 with treatment failure (5.0%) and 5 with relapse after initial treatment completion (3.6%). FQs, such as levofloxacin and moxifloxacin, were given to 75 (53.6%) patients. Favorable treatment outcomes were more frequent for patients who received FQs (97.3% [73/75 patients]) than for those who did not receive FQs (84.6% [55/65 patients]) (P = 0.007). Patients who did not receive FQs were more likely to develop treatment failure (9.2% [6/65 patients] versus 1.3% [1/75 patients]) (P = 0.049) than patients who received FQs. The adjusted proportion of unfavorable outcomes was significantly higher among patients who did not receive FQs (8.8%; 95% confidence interval [CI], 3.3 to 21.5%) than among those who did receive FQs (1.5%; 95% CI, 0.3 to 7.7%) (P = 0.037). These results suggest that the addition of FQs can improve treatment outcomes for patients with INH-resistant pulmonary TB.

Rapid Molecular Detection of Multidrug-Resistant Tuberculosis by PCR-Nucleic Acid Lateral Flow Immunoassay

Several existing molecular tests for multidrug-resistant tuberculosis (MDR-TB) are limited by complexity and cost, hindering their widespread application. The objective of this proof of concept study was to develop a simple Nucleic Acid Lateral Flow (NALF) immunoassay as a potential diagnostic alternative, to complement conventional PCR, for the rapid molecular detection of MDR-TB. The NALF device was designed using antibodies for the indirect detection of labeled PCR amplification products. Multiplex PCR was optimized to permit the simultaneous detection of the drug resistant determining mutations in the 81-bp hot spot region of the rpoB gene (rifampicin resistance), while semi-nested PCR was optimized for the S315T mutation detection in the katG gene (isoniazid resistance). The amplification process additionally targeted a conserved region of the genes as Mycobacterium tuberculosis (Mtb) DNA control. The optimized conditions were validated with the H37Rv wild-type (WT) Mtb isolate and Mtb isolates with known mutations (MT) within the rpoB and katG genes. Results indicate the correct identification of WT (drug susceptible) and MT (drug resistant) Mtb isolates, with the least limit of detection (LOD) being 10⁴ genomic copies per PCR reaction. NALF is a simple, rapid and low-cost device suitable for low resource settings where conventional PCR is already employed on a regular basis. Moreover, the use of antibody-based NALF to target primer-labels, without the requirement for DNA hybridization, renders the device generic, which could easily be adapted for the molecular diagnosis of other infectious and non-infectious diseases requiring nucleic acid detection.

Evolution of Extensively Drug-Resistant Tuberculosis over Four Decades: Whole Genome Sequencing and Dating Analysis of Mycobacterium tuberculosis Isolates from KwaZulu-Natal

BACKGROUND

The continued advance of antibiotic resistance threatens the treatment and control of many infectious diseases. This is exemplified by the largest global outbreak of extensively drug-resistant (XDR) tuberculosis (TB) identified in Tugela Ferry, KwaZulu-Natal, South Africa, in 2005 that continues today. It is unclear whether the emergence of XDR-TB in KwaZulu-Natal was due to recent inadequacies in TB control in conjunction with HIV or other factors. Understanding the origins of drug resistance in this fatal outbreak of XDR will inform the control and prevention of drug-resistant TB in other settings. In this study, we used whole genome sequencing and dating analysis to determine if XDR-TB had emerged recently or had ancient antecedents.

METHODS AND FINDINGS

We performed whole genome sequencing and drug susceptibility testing on 337 clinical isolates of Mycobacterium tuberculosis collected in KwaZulu-Natal from 2008 to 2013, in addition to three historical isolates, collected from patients in the same province and including an isolate from the 2005 Tugela Ferry XDR outbreak, a multidrug-resistant (MDR) isolate from 1994, and a pansusceptible isolate from 1995. We utilized an array of whole genome comparative techniques to assess the relatedness among strains, to establish the order of acquisition of drug resistance mutations, including the timing of acquisitions leading to XDR-TB in the LAM4 spoligotype, and to calculate the number of independent evolutionary emergences of MDR and XDR. Our sequencing and analysis revealed a 50-member clone of XDR M. tuberculosis that was highly related to the Tugela Ferry XDR outbreak strain. We estimated that mutations conferring isoniazid and streptomycin resistance in this clone were acquired 50 y prior to the Tugela Ferry outbreak (katG S315T [isoniazid]; gidB 130 bp deletion [streptomycin]; 1957 [95% highest posterior density (HPD): 1937-1971]), with the subsequent emergence of MDR and XDR occurring 20 y (rpoB L452P [rifampicin]; pncA 1 bp insertion [pyrazinamide]; 1984 [95% HPD: 1974-1992]) and 10 y (rpoB D435G [rifampicin]; rrs 1400 [kanamycin]; gyrA A90V [ofloxacin]; 1995 [95% HPD: 1988-1999]) prior to the outbreak, respectively. We observed frequent de novo evolution of MDR and XDR, with 56 and nine independent evolutionary events, respectively. Isoniazid resistance evolved before rifampicin resistance 46 times, whereas rifampicin resistance evolved prior to isoniazid only twice. We identified additional putative compensatory mutations to rifampicin in this dataset. One major limitation of this study is that the conclusions with respect to ordering and timing of acquisition of mutations may not represent universal patterns of drug resistance emergence in other areas of the globe.

CONCLUSIONS

In the first whole genome-based analysis of the emergence of drug resistance among clinical isolates of M. tuberculosis, we show that the ancestral precursor of the LAM4 XDR outbreak strain in Tugela Ferry gained mutations to first-line drugs at the beginning of the antibiotic era. Subsequent accumulation of stepwise resistance mutations, occurring over decades and prior to the explosion of HIV in this region, yielded MDR and XDR, permitting the emergence of compensatory mutations. Our results suggest that drug-resistant strains circulating today reflect not only vulnerabilities of current TB control efforts but also those that date back 50 y. In drug-resistant TB, isoniazid resistance was overwhelmingly the initial resistance mutation to be acquired, which would not be detected by current rapid molecular diagnostics employed in South Africa that assess only rifampicin resistance.

Cost Resulting from Anti-Tuberculosis Drug Shortages in the United States: A Hypothetical Cohort Study

Background

From 2012 through 2014, the United States experienced acute shortages and price escalations of several first-line anti-tuberculosis (TB) medications. Because secondary TB drug regimens are longer and adverse events occur more frequently with them, we sought to conservatively estimate the cost, to patients and the health care system, of TB treatment and medication adverse events from alternative regimens during drug shortages.

Methods

We assessed the cost of treatment for TB disease in the absence of isoniazid (INH), rifampin (RIF), or pyrazinamide (PZA), or both INH and RIF. We simulated adverse events based on published probabilities using a monthly discrete-time stochastic model. For total costs, we summed costs of medications, routine testing, and treatment of adverse events using procedural terminology codes. We report average cost ratios of TB treatment during drug shortages to standard TB treatment.

Results

The cost ratio of TB treatment without INH, RIF, or PZA to standard treatment was 1.7 (Range: 1.2, 2.3), 4.9 (Range: 3.2, 7.3), and 1.1 (Range: 0.7, 1.7) times higher, respectively. Without both INH and RIF, the cost ratio was 18.6 (Range: 10.0, 39.0) times higher. When the prices for INH, RIF and PZA were increased, the cost for standard treatment increased by a factor of 2.7 (Range: 1.9, 3.0). The percentage of patients experiencing at least one adverse event while taking standard therapy was 3.9% (Range: 1.3%, 11.8%). This percentage increased to 51.5% (Range: 20.1%, 83.8%) when RIF was unavailable, and increased to 82.5% (Range: 41.2%, 98.5%) when both INH and RIF were unavailable.

Conclusions

Our conservative model illustrates that an interruption in first-line anti-TB medications leads to appreciable additional costs and adverse events for patients. The availability of these drugs in the United States should be ensured. Models that incorporate the effectiveness of alternative regimens, delays in treatment initiation, and TB transmission can provide broader perspectives on the impact of drug shortages.

First insights into circulating Mycobacterium tuberculosis complex lineages and drug resistance in Guinea

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First insight into resistance levels and genetic diversity of TB in Guinea.

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Rapid expansion of drug-resistance prone LAM10 Cameroon family.

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Population structure reveals less ‘ancestral’ TB than in surrounding countries.

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Knowledge of genetic diversity is relevant for tuberculosis control programs.

In this study we assessed first-line anti-tuberculosis drug resistance and the genotypic distribution of Mycobacterium tuberculosis complex (MTBC) isolates that had been collected from consecutive new tuberculosis patients enrolled in two clinical trials conducted in Guinea between 2005 and 2010. Among the total 359 MTBC strains that were analyzed in this study, 22.8% were resistant to at least one of the first line anti-tuberculosis drugs, including 2.5% multidrug resistance and 17.5% isoniazid resistance, with or without other drugs. In addition, further characterization of isolates from a subset of the two trials (n = 184) revealed a total of 80 different spoligotype patterns, 29 “orphan” and 51 shared patterns. We identified the six major MTBC lineages of human relevance, with predominance of the Euro-American lineage. In total, 132 (71.7%) of the strains were genotypically clustered, and further analysis (using the DESTUS model) suggesting significantly faster spread of LAM10_CAM family (p = 0.00016). In conclusion, our findings provide a first insight into drug resistance and the population structure of the MTBC in Guinea, with relevance for public health scientists in tuberculosis control programs.

A prospective study of tuberculosis drug susceptibility in sabah, malaysia, and an algorithm for management of isoniazid resistance

Introduction. The burden of tuberculosis is high in eastern Malaysia, and rates of Mycobacterium tuberculosis drug resistance are poorly defined. Our objectives were to determine M. tuberculosis susceptibility and document management after receipt of susceptibility results. Methods. Prospective study of adult outpatients with smear-positive pulmonary tuberculosis (PTB) in Sabah, Malaysia. Additionally, hospital clinicians accessed the reference laboratory for clinical purposes during the study. Results. 176 outpatients were enrolled; 173 provided sputum samples. Mycobacterial culture yielded M. tuberculosis in 159 (91.9%) and nontuberculous Mycobacterium (NTM) in three (1.7%). Among outpatients there were no instances of multidrug resistant M. tuberculosis (MDR-TB). Seven people (4.5%) had isoniazid resistance (INH-R); all were switched to an appropriate second-line regimen for varying durations (4.5-9 months). Median delay to commencement of the second-line regimen was 13 weeks. Among 15 inpatients with suspected TB, 2 had multidrug resistant TB (one extensively drug resistant), 2 had INH-R, and 4 had NTM. Conclusions. Current community rates of MDR-TB in Sabah are low. However, INH-resistance poses challenges, and NTM is an important differential diagnosis in this setting, where smear microscopy is the usual diagnostic modality. To address INH-R management issues in our setting, we propose an algorithm for the treatment of isoniazid-resistant PTB.

Isoniazid-resistant tuberculosis in Birmingham, United Kingdom, 1999-2010

BACKGROUND

There have been few studies on risk factors and treatment outcomes of isoniazid (H)-resistant tuberculosis (TB), and optimal treatment regimens are debated.

AIM

: To identify risk factors for H-resistant TB, describe treatment regimens and compare these to national guidelines and describe short-term outcomes of H-resistant TB in Birmingham, UK.

DESIGN

Retrospective case series.

METHODS

Cases of H-resistant tuberculosis in Birmingham between January 1999 and December 2010 (n = 89) were compared with drug-susceptible cases (n = 2497). Treatment regimens and outcomes at 12 months from diagnosis were evaluated by case note review.

RESULTS

No independent predictors for H-resistant TB were found. For 76/89 (85%) patients with full treatment details available, median treatment duration was 11 months (interquartile range 9-12 months). Only 27/72 (38%) patients with H-monoresistance were treated in line with national guidelines. A further 14/72 (19%) were treated according to other recognized guidelines. Overall treatment success was 75/89 (84%). Treatment failure occurred in 6/89 (7%) patients, all developed multi-drug resistance. Poor adherence was documented in these patients and use of a non-standard regimen in one patient was not thought to have contributed to treatment failure.

CONCLUSIONS

No discriminating risk factors for early detection of H-resistant TB were found. Treatment regimens in clinical practice were highly varied. H-resistance can drive MDR-TB when there is evidence or suspicion of poor adherence. A low threshold for enhanced case management with directly observed therapy is warranted in this group.