*2.2.5. Cured*

A patient who has completed a course of anti-TB treatment according to programme protocol and has at least five consecutive negative cultures from samples collected at least 30 days apart in the final 12 months of treatment. If only one positive culture is reported during that time, and there is no concomitant clinical evidence of deterioration, a patient may still be considered cured, provided that this positive culture is followed by a minimum of three consecutive negative cultures taken at least 30 days apart.

The review of Cohn et al, 1997 represented a comprehensive description of worldwide drug resistance surveys performed during the 1990s. According to the study, resistance to multiple drugs varied by geographic region and was more common when resistance was acquired rather than primary. The rate of multidrug resistance (and occasionally other drugs) was low in most surveys of primary resistance, ranging from 0 to 10.8% (median rate, 0.5%); however, for acquired resistance, the rate of multidrug resistance ranged from 0 to 48.0% (median rate, 12.2%). For surveys that did not distinguish between primary and acquired resistance, the range was 0.5% to 14.3% (median rate, 2.3%). In terms of antituberculous drug resistance, they found a great deal of variability between different countries, and within some countries,

Epidemiology of Multidrug Resistant Tuberculosis (MDR-TB)

http://dx.doi.org/10.5772/54882

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The review of Caminero et al of 2010 [14], broadly discuss the epidemiological data of the global report, issued in 2008. The report included drug susceptibility data from 90 726 patients in 83 countries and territories from year 2002 to 2007. The median prevalence of resistance in new cases of TB was 11.1% for any drug and 1.6% for MDR-TB. The prevalence of MDR-TB in new TB cases ranged from 0% in eight countries to 22.3% in Baku, Azerbaijan, and 19.4% in the Republic of Moldova. Of the 20 settings with the highest proportion of MDR-TB in new cases, 14 were located in countries of the former Soviet Union (between 6.8% and 22.3% in nine countries, including Moldovia and Azerbaijan) and four in China (7% in two provinces in China) [15, 16], A trend analysis of the 2008 report shows that between 1994 and 2007 the prevalence of MDR-TB in new cases (initial resistance) increased substantially in South Korea and two Russian Oblasts, Tomsk and Orel. By contrast, the prevalence remained stable in Estonia and Latvia, both of which have high rates of initial MDR-TB. The prevalence of MDR-

Of 37 countries and territories that reported representative data on XDR-TB, five countries, all from the former Soviet Union, each reported 25 or more cases of XDR-TB, with MDR-TB prevalence ranging from 6.6% to 23.7% [15, 16], data from Eastern Mediterranean countries showed that the prevalence of initial MDR-TB was higher than previously estimated, with the exception of Morocco and Lebanon, with rates of respectively 0.5% and 1.1%. Initial MDR-TB rates in Jordan and Yemen were respectively 5.4% and 2.9%. The Americas, Central Europe and Africa reported the lowest rates of initial MDR-TB, with the notable exceptions of Peru, Rwanda and Guatemala, which reported rates of respectively 5.3%, 3.9% and 3.0%. [15, 16]. Data on previously treated cases from the WHO/ Union 2008 report were available for 66 countries and two regions of China [15]. Drug susceptibility testing (DST) results were available for 12 977 patients. Resistance to at least one anti-tuberculosis drug ranged from 0% in three European countries to 85.9% in Tashkent, Uzbekistan. The highest proportions of MDR-TB were reported in Tashkent (60.0%) and Baku, Azerbaijan (55.8%). data from Gujarat State, India, providing the first reliable descriptions of previously treated cases in India,

The 2008 WHO/Union report also included a global estimation of the MDR-TB problem [14]. Based on drug resistance data from 114 countries and two regions of China reporting to this project, combined with nine other epidemiological factors, the proportion of MDR-TB among new, previously treated and combined cases was estimated for countries with no survey

TB in all TB cases decreased in Hong Kong and the United States [14].

differences between regions or cities [13].

showed 17.2% MDR-TB in this group [15].

#### *2.2.6. Failed*

Anti-TB treatment will be considered to have failed if two or more of the five cultures recorded in the final 12 months of therapy are positive, or if any one of the final three cultures is positive. Treatment will also be considered to have failed if a clinical decision has been made to terminate treatment early because of poor clinical or radiological response or adverse events. These latter failures can be indicated separately in order to do sub-analysis.
