High worldwide drug-resistant TB figures are “worrying

By Sarah Guy, medwireNews Reporter

The prevalence of resistance to second-line therapy among individuals with multi-drug resistant (MDR) tuberculosis is high, show the results of a study conducted using data from eight countries worldwide.

Indeed, the findings reveal a "worrying" risk for extensively MDR forms of the disease, remark Tracy Dalton, from the US Centers for Disease Control and Prevention in Atlanta, Georgia, and colleagues in The Lancet.

Almost half of the more than 1000 patients whose data were included in the study showed resistance to at least one second-line drug, examples of which include second-line fluoroquinolones, injectable kanamycin and capreomycin, and oral aminosalicylic acid, reports the team.

"Our country-specific results can be extrapolated to guide in-country policy for laboratory capacity and for designing effective treatment recommendations for MDR tuberculosis," suggest Dalton et al.

A total of 1278 adult tuberculosis patients treated between January 2005 and December 2008 from Estonia, Latvia, Peru, Philippines, Russia, South Africa, South Korea, and Thailand were included in the analysis.

In all, 43.7% showed resistance to at least one second-line drug, 20.0% to at least one second-line injectable drug, and 12.9% to at least one fluoroquinolone, report the authors. The rate of extensively MDR tuberculosis was 6.7% across the eight countries.

The prevalence of drug resistance correlated directly with the time that second-line drugs have been available in that country, note Dalton and co-investigators, with the lowest rates of resistance seen in Thailand, the Philippines, and Peru, where the drugs have been available for 7, 9, and 10 years, respectively.

Overall, the most significant predictor of resistance to second-line therapy was receiving previous treatment with second-line drugs, with risk ratios for resistance to fluoroquinolones ranging from 3.27 to 4.81, ratios for resistance to second-line injectables ranging from 1.53 to 2.03, ratios for resistance to oral second-line drugs ranging from 1.58 to 2.31, and risk ratios for having extensively MDR tuberculosis ranging from 4.05 to 4.75.

Participants who were inpatients at the time of enrollment to the study (ranging from 0.6% to 100.0% per country) had a higher risk for resistance than outpatients, possibly due to nosocomial transmission of tuberculosis or disease severity, contend the researchers.

Finally, resistance to second-line injectables was associated with factors including imprisonment, unemployment, and alcohol abuse, leading the team to suggest that social factors should be taken into account in the management of tuberculosis.

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