Tuberculosis Multidrug-resistant Tuberculosis – From Epidemiology to Treatment Design

Abstract

Multidrug-resistant tuberculosis (MDR-TB) and extensively resistant tuberculosis (XDR-TB) are present in most regions of the world and represent a serious threat to the control of tuberculosis. They usually result from errors somewhere along the chain of management of the disease that favoured the selection of resistant mutants, progressively replacing drug-sensitive strains and transmitted to further patients. The currently recommended strategies for the control of this serious situation is the rapid identification of drug-resistant strains, careful drug management of patients with second-line drugs and prevention of the transmission of mycobacteria to contacts. Optimal selection and number of drugs and duration of treatment are not clearly defined. Prevention of the creation of additional cases of MDR-TB is crucial. KeywordsTuberculosis, multidrug-resistant tuberculosis (MDR-TB), extensively resistant tuberculosis (XDR-TB), treatment Disclosure: Jean-Pierre Zellweger has no conflicts of interest to declare. No funding was received for the publication of this article.Open Access: This article is published under the Creative Commons Attribution Noncommercial License, which permits any non-commercial use, distribution, adaptation and reproduction provided the original author(s) and source are given appropriate credit. The latest reports from the World Health Organization (WHO) estimate the number of MDR-TB to half a million cases, of which 10 % are XDR-TB, a large part being left untreated, with a high death burden.2 In some regions of the world or in some at-risk populations, like gold miners in South Africa, the rate of MDR-TB is increasing rapidly, particularly in previously treated cases, in spite of the fact that the global incidence rate in the same population had decreased during the same time period.3 Recent reports reveal alarming levels of drug-resistant TB in many Eastern European regions, 4 such as Belarus, where the rates reach 35.3 % in new patients and 76.5 % among previously treated cases 5 or in Ukraine, where the association with HIV seems to increase the problem. 6 In Russia, if the current trends continue, the incidence of drug-resistant TB could be higher than the incidence of drug-sensitive TB within the next few years.7 Prisons seem to be places where the incidence of TB (including drug-resistant forms) is particularly high. 7,8 In China, a recent survey concluded that the proportion of MDR-TB cases among new and previously treated patients is 5.7 % and 25.6 %, respectively, and the total number of MDR-TB cases is about 110,000. 9 The increase in drugresistant TB is also observed in children in some regions of the world.