Hans L. Rieder

Short, Highly Effective, and Inexpensive Standardized Treatment of Multidrug-resistant Tuberculosis

RATIONALEnBased on expert opinion, the global guidelines for management of multidrug-resistant tuberculosis impose lengthy and often poorly tolerated treatments.nnnOBJECTIVESnThis observational study evaluates the effectiveness of standardized regimens for patients with proven multidrug-resistant tuberculosis previously untreated with second-line drugs in low-income countries.nnnMETHODSnConsenting patients were sequentially assigned to one of six standardized treatment regimens. Subsequent cohorts were treated with regimens adapted according to results in prior cohorts. The study was designed to minimize failure and default while reducing total treatment duration without increasing relapse frequency.nnnMEASUREMENTS AND MAIN RESULTSnWe report the treatment outcome of all patients with laboratory-confirmed, multidrug-resistant tuberculosis enrolled from May 1997 to December 2007. The most effective treatment regimen required a minimum of 9 months of treatment with gatifloxacin, clofazimine, ethambutol, and pyrazinamide throughout the treatment period supplemented by prothionamide, kanamycin, and high-dose isoniazid during an intensive phase of a minimum of 4 months, giving a relapse-free cure of 87.9% (95% confidence interval, 82.7-91.6) among 206 patients. Major adverse drug reactions were infrequent and manageable. Compared with the 221 patients treated with regimens based on ofloxacin and commonly prothionamide throughout, the hazard ratio of any adverse outcome was 0.39 (95% confidence interval, 0.26-0.59).nnnCONCLUSIONSnSerial regimen formulation guided by overall treatment effectiveness resulted in treatment outcomes comparable to those obtained with first-line treatment. Confirmatory formal trials in populations with high levels of human immunodeficiency virus coinfection and in populations with a higher initial prevalence of resistance to second-line drugs are required.

Successful '9-month Bangladesh regimen' for multidrug- resistant tuberculosis among over 500 consecutive patients

SETTINGnTuberculosis (TB) program, Damien Foundation Projects, Bangladesh.nnnOBJECTIVEnTo summarize the outcome and its determinants of the first treatment for multidrug-resistant TB using a standardized regimen consisting of a minimum 9 months.nnnDESIGNnThis was a prospective, observational study of a gatifloxacin (GFX) based directly observed regimen, mainly with initial hospitalization. The 4-month intensive phase was extended until sputum smear conversion. Patients were monitored using culture for up to 2 years after treatment completion.nnnRESULTSnOf the 515 patients who met the study inclusion criteria and were successively enrolled from 2005 to 2011, 84.4% had a bacteriologically favorable outcome. Due to extensive disease with delayed sputum conversion, only half of the patients completed treatment within 9 months; however, 95% were able to complete treatment within 12 months. Eleven patients failed or relapsed, and 93.1% of the 435 patients who were successfully treated completed at least 12 months post-treatment follow-up. The strongest risk factor for a bacteriologically unfavorable outcome was high-level fluoroquinolone (FQ) resistance, particularly when compounded by initial pyrazinamide (PZA) resistance. Low-level FQ resistance had no unfavorable effect on treatment outcome. Amplification of drug resistance occurred only once, in a patient strain that was initially only susceptible to kanamycin and clofazimine.nnnCONCLUSIONnThe excellent outcome of the Bangladesh regimen was largely maintained. Bacteriological treatment failures and relapses were rare, except among patients with high-level GFX resistance, notably in the presence of PZA resistance.

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.

Tracking a Tuberculosis Outbreak Over 21 Years: Strain-Specific Single-Nucleotide Polymorphism Typing Combined With Targeted Whole-Genome Sequencing

BACKGROUNDnWhole-genome sequencing (WGS) is increasingly used in molecular-epidemiological investigations of bacterial pathogens, despite cost- and time-intensive analyses. We combined strain-specific single-nucleotide polymorphism (SNP) typing and targeted WGS to investigate a tuberculosis cluster spanning 21 years in Bern, Switzerland.nnnMETHODSnOn the basis of genome sequences of 3 historical outbreak Mycobacterium tuberculosis isolates, we developed a strain-specific SNP-typing assay to identify further cases. We screened 1642 patient isolates and performed WGS on all identified cluster isolates. We extracted SNPs to construct genomic networks. Clinical and social data were retrospectively collected.nnnRESULTSnWe identified 68 patients associated with the outbreak strain. Most received a tuberculosis diagnosis in 1991-1995, but cases were observed until 2011. Two thirds were homeless and/or substance abusers. Targeted WGS revealed 133 variable SNP positions among outbreak isolates. Genomic network analyses suggested a single origin of the outbreak, with subsequent division into 3 subclusters. Isolates from patients with confirmed epidemiological links differed by 0-11 SNPs.nnnCONCLUSIONSnStrain-specific SNP genotyping allowed rapid and inexpensive identification of M. tuberculosis outbreak isolates in a population-based strain collection. Subsequent targeted WGS provided detailed insights into transmission dynamics. This combined approach could be applied to track bacterial pathogens in real time and at high resolution.

An ecological analysis of incidence of tuberculosis and per capita gross domestic product

To the Editor: nnIn 2006, an estimated 9 million new cases of tuberculosis (TB) emerged worldwide 1. Of these, only 1% occurred in the European Union and North America combined, while Africa and South-East Asia contributed >65%. Among the 22 high-burden countries, 17 were in Africa, 16 of which were in the lowest quartile in terms of per capita gross domestic product (GDP). Since 2001, the fight against poverty has been a major theme in the World Health Organization’s (WHO) “Stop TB” strategy. Indeed, poverty “fuels” TB by facilitating transmission through crowded working and living conditions, it may increase the risk of progression to disease through malnutrition, and imposes barriers to accessing health services.nnThe aim of the present analysis …

HIV Infection Disrupts the Sympatric Host–Pathogen Relationship in Human Tuberculosis

The phylogeographic population structure of Mycobacterium tuberculosis suggests local adaptation to sympatric human populations. We hypothesized that HIV infection, which induces immunodeficiency, will alter the sympatric relationship between M. tuberculosis and its human host. To test this hypothesis, we performed a nine-year nation-wide molecular-epidemiological study of HIV–infected and HIV–negative patients with tuberculosis (TB) between 2000 and 2008 in Switzerland. We analyzed 518 TB patients of whom 112 (21.6%) were HIV–infected and 233 (45.0%) were born in Europe. We found that among European-born TB patients, recent transmission was more likely to occur in sympatric compared to allopatric host–pathogen combinations (adjusted odds ratio [OR] 7.5, 95% confidence interval [95% CI] 1.21–infinity, pu200a=u200a0.03). HIV infection was significantly associated with TB caused by an allopatric (as opposed to sympatric) M. tuberculosis lineage (OR 7.0, 95% CI 2.5–19.1, p<0.0001). This association remained when adjusting for frequent travelling, contact with foreigners, age, sex, and country of birth (adjusted OR 5.6, 95% CI 1.5–20.8, pu200a=u200a0.01). Moreover, it became stronger with greater immunosuppression as defined by CD4 T-cell depletion and was not the result of increased social mixing in HIV–infected patients. Our observation was replicated in a second independent panel of 440 M. tuberculosis strains collected during a population-based study in the Canton of Bern between 1991 and 2011. In summary, these findings support a model for TB in which the stable relationship between the human host and its locally adapted M. tuberculosis is disrupted by HIV infection.

Scaling Up Programmatic Management of Drug-Resistant Tuberculosis: A Prioritized Research Agenda

Frank Cobelens and colleagues outline key research questions that need to be addressed to maximize the impact of programmatic management of drug-resistant tuberculosis.

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.

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 mutantsu200a+u200a94Ala) [ORu200a=u200a4.3 (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.

Mycobacterium tuberculosis transmission in a country with low tuberculosis incidence: Role of immigration and HIV infection

ABSTRACT Immigrants from high-burden countries and HIV-coinfected individuals are risk groups for tuberculosis (TB) in countries with low TB incidence. Therefore, we studied their role in transmission of Mycobacterium tuberculosis in Switzerland. We included all TB patients from the Swiss HIV Cohort and a sample of patients from the national TB registry. We identified molecular clusters by spoligotyping and mycobacterial interspersed repetitive-unit–variable-number tandem-repeat (MIRU-VNTR) analysis and used weighted logistic regression adjusted for age and sex to identify risk factors for clustering, taking sampling proportions into account. In total, we analyzed 520 TB cases diagnosed between 2000 and 2008; 401 were foreign born, and 113 were HIV coinfected. The Euro-American M. tuberculosis lineage dominated throughout the study period (378 strains; 72.7%), with no evidence for another lineage, such as the Beijing genotype, emerging. We identified 35 molecular clusters with 90 patients, indicating recent transmission; 31 clusters involved foreign-born patients, and 15 involved HIV-infected patients. Birth origin was not associated with clustering (adjusted odds ratio [aOR], 1.58; 95% confidence interval [CI], 0.73 to 3.43; P = 0.25, comparing Swiss-born with foreign-born patients), but clustering was reduced in HIV-infected patients (aOR, 0.49; 95% CI, 0.26 to 0.93; P = 0.030). Cavitary disease, male sex, and younger age were all associated with molecular clustering. In conclusion, most TB patients in Switzerland were foreign born, but transmission of M. tuberculosis was not more common among immigrants and was reduced in HIV-infected patients followed up in the national HIV cohort study. Continued access to health services and clinical follow-up will be essential to control TB in this population.