Specific gyrA gene mutations predict poor treatment outcome in MDR-TB.

OBJECTIVES: Mutations in the gyrase genes cause fluoroquinolone resistance in Mycobacterium tuberculosis. However, the predictive value of these markers for clinical outcomes in patients with MDR-TB is unknown to date. The objective of this study was to determine molecular markers and breakpoints predicting second-line treatment outcomes in M. tuberculosis patients treated with fourth-generation fluoroquinolones. METHODS: We analysed treatment outcome data in relation to the gyrA and gyrB sequences and MICs of ofloxacin, gatifloxacin and moxifloxacin for pretreatment M. tuberculosis isolates from 181 MDR-TB patients in Bangladesh whose isolates were susceptible to injectable drugs. RESULTS: The gyrA 90Val, 94Gly and 94Ala mutations were most frequent, with the highest resistance levels for 94Gly mutants. Increased pretreatment resistance levels (>2 mg/L), related to specific mutations, were associated with lower cure percentages, with no cure in patients whose isolates were resistant to gatifloxacin at 4 mg/L. Any gyrA 94 mutation, except 94Ala, predicted a significantly lower proportion of cure compared with all other gyrA mutations taken together (all non-94 mutants + 94Ala) [OR = 4.3 (95% CI 1.4-13.0)]. The difference in treatment outcome was not explained by resistance to the other drugs. CONCLUSIONS: Our study suggests that gyrA mutations at position 94, other than Ala, predict high-level resistance to gatifloxacin and moxifloxacin, as well as poor treatment outcome, in MDR-TB patients in whom an injectable agent is still effective.

Molecular epidemiology of tuberculosis in Cambodian children.

SUMMARY We analysed Mycobacterium tuberculosis strains from children, hospitalized from January 2004 to July 2008 in the largest paediatric hospital complex in Cambodia. Specimens were tested for drug susceptibility and genotypes. From the 260 children, 161 strains were available. The East African-Indian genotype family was the most common (59.0%), increasing in frequency with distance from the Phnom Penh area, while the frequency of the Beijing genotype family strains decreased. The drug resistance pattern showed a similar geographical gradient: lowest in the northwest (4.6%), intermediate in the central (17.1%), and highest in the southeastern (30.8%) parts of the country. Three children (1.9%) had multidrug-resistant tuberculosis. The Beijing genotype and streptomycin resistance were significantly associated (P < 0.001). As tuberculosis in children reflects recent transmission patterns in the community, multidrug resistance levels inform about the current quality of the tuberculosis programme.

Treatment of latent infection with Mycobacterium tuberculosis: update 2010.

Much remains unknown about latent infection with Mycobacterium tuberculosis. Existing immunodiagnostic tools for this condition have various limitations, most importantly in their ability to predict disease. Randomised controlled trials have established protective efficacy of isoniazid therapy for 6-12 months among non-HIV-infected and HIV-infected subjects. While efficacy may reach 90%, acceptance and adherence to prolonged therapy are less than desired. Rifampicin plus pyrazinamide for 2 months, though efficacious, has been associated with excess hepatotoxicity in non-HIV-infected persons. Isoniazid plus rifampicin for 3 months has proven efficacy, but adverse effects may be more frequent than isoniazid or rifampicin monotherapy. Rifampicin monotherapy for 3-4 months is well tolerated, but efficacy data are currently limited, and concerns remain over possible selection of rifampicin-resistant mutants. For contacts of patients with multidrug-resistant tuberculosis, expert opinions differ on whether to treat with at least two drugs or just a fluoroquinolone, and for how long. With the existing diagnostic and treatment tools, efficacy of preventive therapy does not necessarily translate into field effectiveness. A targeted approach is required to maximise cost-effectiveness. Each geographic region needs to set its own priority after taking into account available scientific data and local circumstances.

Harmonisation of TB control in the WHO European region: the history of the Wolfheze Workshops.

In 1990 a workshop was organised in the village of Wolfheze (the Netherlands), where experts discussed the critical interventions that would foster elimination of TB in Europe. This event has been followed by several more over the following two decades to become known as the "Wolfheze Workshops". This article provides a brief overview of the history and the impact the Wolfheze Workshops have had on the commitment of European governments to standardise definitions, recording and reporting systems and, thus, permitted comparison of interventions and improving TB control across borders. The Wolfheze Workshops have been and still are an essential platform for this exchange of experiences, promoting common approaches.

Tuberculosis contact investigation in low prevalence countries: a European consensus.

Contact investigation to identify individuals with tuberculosis and latent infection with Mycobacterium tuberculosis is an important component of tuberculosis control in low tuberculosis incidence countries. This document provides evidence-based and best-practice policy recommendations for contact tracing among high- and medium-priority contacts in a variety of settings. It provides a basis for national guidelines on contact investigation and tuberculosis outbreak management, and should support countries and tuberculosis control managers in evaluating and revising national policies. A review of existing guidelines, a literature search, several meetings and consultation with experts were used to formulate and grade recommendations for action during contact investigation. Available tests to identify individuals with latent infection with M. tuberculosis are designed to identify immune response against mycobacterial antigens and have variable predictive value for the likelihood to develop active tuberculosis in different populations. Contact investigation should therefore be limited to situations with a clear likelihood of transmission or to those with a higher probability of developing active tuberculosis, for instance, young children and immunocompromised persons. A risk assessment-based approach is recommended, where the need to screen contacts is prioritised on the basis of the infectiousness of the index case, intensity of exposure and susceptibility of contacts.

The risk of tuberculosis related to tumour necrosis factor antagonist therapies: a TBNET consensus statement.

Anti-tumour necrosis factor (TNF) monoclonal antibodies or soluble TNF receptors have become an invaluable treatment against chronic inflammatory diseases, such as rheumatoid arthritis, inflammatory bowel disease and psoriasis. Individuals who are treated with TNF antagonists are at an increased risk of reactivating latent infections, especially tuberculosis (TB). Following TNF antagonist therapy, the relative risk for TB is increased up to 25 times, depending on the clinical setting and the TNF antagonist used. Interferon-γ release assays or, as an alternative in individuals without a history of bacille Calmette-Guérin vaccination, tuberculin skin testing is recommended to screen all adult candidates for TNF antagonist treatment for the presence of latent infection with Mycobacterium tuberculosis. Moreover, paediatric practice suggests concomitant use of both the tuberculin skin test and an interferon-γ release assay, as there are insufficient data in children to recommend one test over the other. Consequently, targeted preventive chemotherapy is highly recommended for all individuals with persistent M. tuberculosis-specific immune responses undergoing TNF antagonist therapy as it significantly reduces the risk of progression to TB. This TBNET consensus statement summarises current knowledge and expert opinions and provides evidence-based recommendations to reduce the TB risk among candidates for TNF antagonist therapy.

When to start treatment? Dilemma illustrated by a paediatric case of extensively drug-resistant tuberculosis of the central nervous system.

An HIV-positive mother infected her daughter with extensively drug-resistant Mycobacterium tuberculosis. Despite adhering to the then current guidelines for prevention, the infant was diagnosed with extensively drug-resistant pulmonary tuberculosis at the age of 4 months and developed tuberculous meningitis. After a short delay, appropriate treatment was initiated, followed by an inhospital stay at a specialised hospital. The infant became generally well, but had delayed neurological development. Secondary hydrocephalus due to tuberculous meningitis required a ventriculoperitoneal shunt. After 2 years of microbiologically and clinically effective tuberculosis treatment and several shunt complications, the HIV-negative child died at the age of 28 months ‒ with radiological signs of a shunt infection. The reason for the fatal outcome was probably related to inadequate risk reduction of airborne mother-to-child transmission, inappropriate chemoprophylaxis and delayed initiation of adequate treatment.

Seasonality of tuberculosis in an Eastern-Asian country with an extreme continental climate.

Aggregate monthly notifications of incident sputum smear-positive tuberculosis (TB) in Mongolia, stratified by sex and age groups, were analysed separately for Ulaanbaatar, Mongolia, and the rest of the country for the 9-yr period from 1998 to 2006. TB notifications were compared with ambient surface temperature. More than twice as many TB cases were notified in the peak month (April) compared with the trough months (October-December), paralleling the temperature curve. The fluctuations recurred consistently over the entire observation period, were identical in the capital compared with the rest of the country, and were independent of age and sex. TB notifications parallel the temperature amplitudes and have a magnitude not reported elsewhere. We hypothesise that the influence of temperature on life either indoors or outdoors is consistent with the transmission probability of Mycobacterium tuberculosis and the subsequent delay to disease recognition and notification with the incubation period, possibly co-determined by other factors, rather than accessibility to services.

LTBI: latent tuberculosis infection or lasting immune responses to M. tuberculosis? A TBNET consensus statement.

Tuberculosis control relies on the identification and preventive treatment of individuals who are latently infected with Mycobacterium tuberculosis. However, direct identification of latent tuberculosis infection is not possible. The diagnostic tests used to identify individuals latently infected with M. tuberculosis, the in vivo tuberculin skin test and the ex vivo interferon-gamma release assays (IGRAs), are designed to identify an adaptive immune response against, but not necessarily a latent infection with, M. tuberculosis. The proportion of individuals who truly remain infected with M. tuberculosis after tuberculin skin test or IGRA conversion is unknown. It is also uncertain how long adaptive immune responses towards mycobacterial antigens persist in the absence of live mycobacteria. Clinical management and public healthcare policies for preventive chemotherapy against tuberculosis could be improved, if we were to gain a better understanding on M. tuberculosis latency and reactivation. This statement by the TBNET summarises knowledge and limitations of the currently available tests used in adults and children for the diagnosis of latent tuberculosis infection. In summary, the main issue regarding testing is to restrict it to those who are known to be at higher risk of developing tuberculosis and who are willing to accept preventive chemotherapy.

Annual meeting of the Tuberculosis Surveillance and Research Unit, 2008.

The Tuberculosis Surveillance and Research Unit (TSRU) held its last annual meeting in Helsinki, Finland, from 1 to 4 April 2008. Several topics of current interest for tuberculosis (TB) research and new research projects were presented and discussed in depth by 60 delegates from Europe, Africa and Asia. This paper summarises some of the highlights of the meeting which may be of interest to epidemiologists and managers active in the field of TB.

Isoniazid preventive therapy for people living with HIV: public health challenges and implementation issues.

Isoniazid preventive therapy (IPT) is recognised as an important component of collaborative tuberculosis (TB) and human immunodeficiency virus (HIV) activities to reduce the burden of TB in people living with HIV (PLHIV). However, there has been little in the way of IPT implementation at country level. This failure has resulted in a recent call to arms under the banner title of the 'Three I's' (infection control to prevent nosocomial transmission of TB in health care settings, intensified TB case finding and IPT). In this paper, we review the background of IPT. We then discuss the important challenges of IPT in PLHIV, namely responsibility and accountability for the implementation, identification of latent TB infection, exclusion of active TB and prevention of isoniazid resistance, length of treatment and duration of protective efficacy. We also highlight several research questions that currently remain unanswered. We finally offer practical suggestions about how to scale up IPT in the field, including the need to integrate IPT into a package of care for PLHIV, the setting up of operational projects with the philosophy of 'learning while doing', the development of flow charts for eligibility for IPT, the development and implementation of care prior to antiretroviral treatment, and finally issues around procurement, distribution, monitoring and evaluation. We support the implementation of IPT, but only if it is done in a safe and structured way. There is a definite risk that 'sloppy' IPT will be inefficient and, worse, could lead to the development of multidrug-resistant TB, and this must be avoided at all costs.

Gatifloxacin is superior to levofloxacin and moxifloxacin in shorter treatment regimens for multidrug-resistant TB.

SETTING: Data were collected from patients starting one of the shorter treatment regimens (STRs) for multidrug-resistant tuberculosis (MDR-TB) in Bangladesh, Niger or Cameroon.OBJECTIVE: To estimate the effect of either a gatifloxacin (GFX), moxifloxacin (MFX) or levofloxacin (LVX) based STR on bacteriological effectiveness.DESIGN: Retrospective study of prospectively collected data.RESULTS: Among 1530 patients, bacteriological effectiveness was 96.7% overall. Stratified by treatment with a GFX-, LVX- or MFX-based regimen effectiveness was respectively 97.5%, 95.5% and 94.7%. Compared to those on a GFX-based regimen, the estimated summary odds ratio of having an adverse outcome was more than double (OR 2.05, 95% CI 1.09-3.90) in patients treated with either an LVX-based or MFX-based regimen. After adjusting for initial resistance, patients treated with an LVX-based regimen and MFX-based regimen had respectively a 4.5- and 8.4-fold times larger odds of an adverse bacteriological outcome. None among 859 patients at risk treated with a GFX-based compared to at least 4 of 228 among those on an MFX-based regimen acquired fluoroquinolone resistance.CONCLUSION: GFX-based regimens had superior bacteriological effectiveness than MFX-based or LVX-based regimens. As GFX is currently unavailable in most MDR-TB programs, its reintroduction should be prioritised.

Outcome definitions for multidrug-resistant tuberculosis treated with shorter treatment regimens.

To assess whether the revised 2013 World Health Organization (WHO) definitions for multidrug-resistant tuberculosis (MDR-TB) treatment outcomes apply to shorter treatment regimens in low- and middle-income countries and to propose modified criteria. Criteria for 'failure' and 'cure' outcomes were assessed using data on 1006 patients enrolled in an observational study on the standardised 9-11 month shorter MDR-TB regimen in Africa. Absence of conversion in the intensive phase, a WHO criteria for failure, was the worst performing criterion; reversion had low sensitivity and other criteria provided limited added value. Based on our study results, we propose new definitions for 'treatment failure' as treatment termination or the permanent discontinuation of 2 anti-tuberculosis drugs due to 1) positive culture after 6 months of treatment (except for one isolated positive culture) or 2) at least two consecutive grade 2+ positive sputum smears after 6 months of treatment if culture is not available; and for 'cure' as treatment completion without proof of failure AND two consecutive negative cultures taken 30 days apart, one of which should be after 6 months of treatment. The proposed new definitions are applicable to shorter regimens in low- and middle-income countries, and should also work for the newly recommended longer regimens. .

Sputum smear microscopy in the Xpert® MTB/RIF era.

A balanced perspective is advocated for the assessment and application of the most recent and the oldest diagnostic methods for pulmonary tuberculosis (TB)-the molecular Xpert® MTB/RIF assay and microscopy for acid-fast bacilli. We discuss their respective merits and shortcomings and identify threats that may hamper their use in TB control. Neither test on its own provides all the information needed for diagnosis and treatment monitoring. Considering all aspects important for both individual patient care and disease control, neither seems 'better' than the other. The required advancement of microscopy had already been hampered before the introduction of the GeneXpert technology by unsuccessful and probably misguided attempts to decentralise culture-based diagnosis and drug susceptibility testing. It seems evident that systematic replacement of microscopy by Xpert is not a viable option for the foreseeable future. Instead, the two methods should complement each other to arrive at a comprehensive, accessible and continuous service for a maximum number of patients. This will intrinsically prioritise targeting the most potent transmitters with the worst prognosis, simultaneously offering optimised prospects for efficient TB control. New microscopy and Xpert applications are expected to ultimately make control programmes independent of culture-based methods in diagnosis, treatment monitoring and outcome assessment.

Measuring tuberculosis burden, trends, and the impact of control programmes.

The targets for tuberculosis control, framed within the United Nations' Millennium Development Goals, are to ensure that the incidence per head of tuberculosis is falling by 2015, and that the 1990 prevalence and mortality per head are halved by 2015. In monitoring progress in tuberculosis control, the ultimate aim for all countries is to count tuberculosis cases (incidence) accurately through routine surveillance. Disease prevalence surveys are costly and laborious, but give unbiased measures of tuberculosis burden and trends, and are justified in high-burden countries where many cases and deaths are missed by surveillance systems. Most countries in which tuberculosis is highly endemic do not yet have reliable death registration systems. Verbal autopsy, used in cause-of-death surveys, is an alternative, interim method of assessing tuberculosis mortality, but needs further validation. Although several new assays for Mycobacterium tuberculosis infection have recently been devised, the tuberculin skin test remains the only practical method of measuring infection in populations. However, this test typically has low specificity and is therefore best used comparatively to assess geographical and temporal variation in risk of infection. By 2015, every country should be able to assess progress in tuberculosis control by estimating the time trend in incidence, and the magnitude of reductions in either prevalence or deaths.

Demographic characteristics of patients with extrapulmonary tuberculosis in Germany.

The aim of the present study was to determine the demographics of patients with extrapulmonary tuberculosis in Germany. Data on 26,302 tuberculosis cases from a national survey carried out during the period 1996-2000 were analysed. The crude proportion of tuberculosis patients with extrapulmonary manifestations was 21.6%. Extrapulmonary tuberculosis was most likely among females, children aged <15 yrs and persons originating from Africa and Asia. Females tended to be more likely to have any form of extrapulmonary tuberculosis than males, except pleural tuberculosis. The strength of this association was strongest in the age range 25-64 yrs and less pronounced amongst the oldest patients. Children were particularly prone to the development of lymphatic and meningeal tuberculosis, whereas the likelihood of genitourinary tuberculosis increased with increasing age. Asian and African patients were generally more likely than persons from other areas to have lymphatic, osteoarticular, meningeal and miliary tuberculosis. The analysis shows important differences, by age, sex and origin, in the likelihood of a tuberculosis patient presenting with extrapulmonary tuberculosis. Since the relative contribution of the foreign-born to tuberculosis in low-prevalence countries is rising, extrapulmonary tuberculosis must be taken into account more often in the differential diagnostic work-up of these patients, particularly among those originating from Asia and Africa.

Improving the estimation of tuberculosis infection prevalence using T-cell-based assay and mixture models.

BACKGROUND: The prevalence of latent tuberculosis infection (LTBI) is traditionally estimated using the tuberculin skin test (TST). Highly specific blood-based interferon-gamma release assays (IGRAs) are now available and could enhance the estimation of LTBI prevalence in combination with model-based methods. DESIGN: We compared conventional and model-based methods for estimating LTBI prevalence among 719 Indian health care workers who underwent both TST and QuantiFERON-TB Gold In-Tube (QFT-G). In addition to using standard cut-off points on TST and QFT-G, Bayesian mixture model analyses were performed with: 1) continuous TST data and 2) categorical data using both TST and QFT-G results in a latent class analysis (LCA), accounting for prior information on sensitivity and specificity. RESULTS: Estimates of LTBI prevalence varied from 33.8% to 60.7%, depending on the method used. The mixture model based on TST alone estimated the prevalence at 36.5% (95%CI 28.5-47.0). When results from both tests were combined using LCA, the prevalence was 45.4% (95%CI 39.5-51.1). The LCA provided additional results on the sensitivity, specificity and predictive values of joint results. CONCLUSION: The availability of novel, specific IGRAs and development of methods such as mixture analyses allow a more realistic and informative approach to prevalence estimation.

Ziehl-Neelsen staining: theory and practice.

The information provided in the guidelines of the World Health Organization and the International Union Against Tuberculosis and Lung Disease for Ziehl-Neelsen staining is not practical on a number of points. The advice given here is meant to supplement the guidelines. It is based on experiments on and field experience of basic fuchsin stain and staining solutions.

Making pragmatic sense of data in the tuberculosis laboratory register.

SETTING: Tuberculosis (TB) microscopy network in Moldova, Mongolia, Uganda and Zimbabwe. OBJECTIVE: To evaluate how scrutinising the information recorded in the TB Laboratory Register can assist in improving the performance of the microscopy laboratory network and TB case management. METHODS: Review of records for completeness in registration of age, sex, reason for examination, analysis of variability patterns in serial smears and provision of exemplary statistical process charts of scanty positive results over time in the four countries. RESULTS: A total of 128808 records were analysed. A large proportion of examinees in Uganda (6.9%) and Zimbabwe (3.9%) had no information on sex. The reason for examination was unknown for 7.4%. Among suspects with three smear results with at least one positive result, 56.1% had no variation in the pattern. Statistical process control charts revealed considerable fluctuation in the frequency of scanty positive smears over a calendar year. CONCLUSION: An analysis of information recorded in the TB Laboratory Register not only identifies strengths and weaknesses in the laboratory, it also reveals weaknesses on a much wider scale, in the entire case management system. TB laboratory data can thus demonstrate when, where and what action is indicated, and how performance might be monitored over time.