Burden Of Multidrug-resistant Tuberculosis Research Articles

Trends in multidrug-resistant tuberculosis

Multidrug-resistant tuberculosis (MDR-TB) is an increasing global problem. The extent and burden of MDR-TB varies significantly from country to country and region to region. Globally, about three per cent of all newly diagnosed patients have MDR-TB and the proportion is higher in patients who had previously received anti-tuberculosis (anti-TB) treatment reflecting the failure of programs designed to ensure complete cure of patients with tuberculosis. The management of MDR-TB is a challenge that should be undertaken by experienced clinicians at centers equipped with reliable laboratory services and implementation of DOTS-Plus strategy.

Multidrug-resistant tuberculosis (MDR-TB): epidemiology, prevention and treatment

Multidrug-resistant tuberculosis (MDR-TB) is an increasing global problem, with most cases arising from a mixture of physician error and patient non-compliance during treatment of susceptible TB. The extent and burden of MDR-TB varies significantly from country to country and region to region. As with TB itself, the overwhelming burden of MDR-TB is in high-burden resource-poor countries. The diagnosis depends on confirming the drug susceptibility pattern of isolated organisms, which is often only possible in resource-rich settings. There should be a strong suspicion of drug resistance, including MDR-TB, in persons with a history of prior treatment or in treatment failure cases. Treatment in developed countries is expensive and involves an individualized regimen based on drug susceptibility data and use of reserve drugs. In resource-poor settings a WHO retreatment regimen may be used, but increasingly the move is to a directly observed treatment based 'DOTS-plus' regimen in a supported national TB programme. However, even where such treatment is given, the outcome for patients is significantly worse than that for fully susceptible TB and has a much higher cost.

Modeling epidemics of multidrug-resistant M. tuberculosis of heterogeneous fitness.

Mathematical models have recently been used to predict the future burden of multidrug-resistant tuberculosis (MDRTB). These models suggest the threat of multidrug resistance to TB control will depend on the relative 'fitness' of MDR strains and imply that if the average fitness of MDR strains is considerably less than that of drug-sensitive strains, the emergence of resistance will not jeopardize the success of tuberculosis control efforts. Multidrug resistance in M. tuberculosis is conferred by the sequential acquisition of a number of different single-locus mutations that have been shown to have heterogeneous phenotypic effects. Here we model the impact of initial fitness estimates on the emergence of MDRTB assuming that the relative fitness of MDR strains is heterogeneous. We find that even when the average relative fitness of MDR strains is low and a well-functioning control program is in place, a small subpopulation of a relatively fit MDR strain may eventually outcompete both the drug-sensitive strains and the less fit MDR strains. These results imply that current epidemiological measures and short-term trends in the burden of MDRTB do not provide evidence that MDRTB strains can be contained in the absence of specific efforts to limit transmission from those with MDR disease.

Worldwide incidence of multidrug-resistant tuberculosis.

Planning for tuberculosis (TB) control requires an assessment of the number and distribution of drug-resistant cases. This study used results of resistance surveys from 64 countries, together with data predictive of resistance rates from 72 others, to estimate the number of new multidrug-resistant (MDR) TB cases that occurred in 2000. By these methods, an estimated 273,000 (95% confidence limits, 185,000 and 414,000) new cases of MDR TB occurred worldwide in 2000, 3.2% of all new TB cases. The analysis provides the first comprehensive set of estimates of the MDR TB burden by country and globally.

Multi-drug resistant tuberculosis burden and risk factors: An update

Multi-drug resistant (MDR) tuberculosis is defined as disease caused by Mycobacterium tuberculosis with resistance to at least two anti-tubercular drugs Isoniazid and Rifampicin. Recent surveillance data have revealed that prevalence of the drug resistant tuberculosis has risen to the highest rate ever recorded in the history. Drug resistant tuberculosis generally arises through the selection of mutated strains by inadequate therapy. The most powerful predictor of the presence of MDR-TB is a history of treatment of TB. Shortage of drugs has been one of the most common reasons for the inadequacy of the initial anti-TB regimen, especially in resource poor settings. Other major issues significantly contributing to the higher complexity of the treatment of MDR-TB is the increased cost of treatment. Other factors also play important role in the development of MDR-TB such as poor administrative control on purchase and distribution of the drugs with no proper mechanism on quality control and bioavailability tests. Tuberculosis control program implemented in past has also partially contributed to the development of drug resistance due to poor follow up and infrastructure. The association known for centuries between TB and poverty also applies to MDR-TB, a rather significant inverse association with MDR-TB. Various treatment strategies have been employed, including the use of standardised treatment regimens based upon representative local susceptibility patterns, empirical treatment based upon previous treatment history and local Drug Susceptibility Test (DST) patterns, and individualised treatment designed on the basis of individual DST results.Treatment outcomes among MDR-TB cases have varied widely; a recent survey of five Green Line Committee (GLC) approved sites in resource-limited countries found treatment success rates of 70%. Treatment continues to be limited in the resource poor countries where the demand is high. The ultimate strategy to control multidrug resistant tuberculosis is one that implements comprehensive approach incorporating treatment of multidrug-resistant tuberculosis based upon principles closely related to those of its general DOTS strategy for TB control: sustained political commitment; a rational case-finding strategy including accurate, timely diagnosis through quality assured culture and DST; appropriate treatment strategies that use second-line drugs under proper case management conditions; uninterrupted supply of quality-assured antituberculosis drugs; standardised recording and reporting system.