International study reveals alarming levels of extensively drug-resistant tuberculosis

August 29, 2012

A large, international study published Online First in The Lancet reveals alarming levels of tuberculosis (TB) that are resistant to both first-line and second-line drugs. The findings show high prevalence of resistance to at least one second-line drug (43.7%) among multidrug-resistant (MDR) TB patients from eight countries in Africa, Asia, Europe, and Latin America. Worse still, the study found higher than expected overall levels of extensively drug-resistant (XDR) TB.

"Most international recommendations for have been developed for MDR TB prevalence of up to around 5%. Yet now we face prevalence up to ten times higher in some places, where almost half of the patients with infectious disease are transmitting MDR strains", warns Sven Hoffner from the Swedish Institute for Communicable Disease Control in a linked Comment.

"Drug-resistant TB is more difficult and costly to treat, and more often fatal. Internationally, it is particularly worrisome in areas with fewer resources and less access to effective therapies. As more individuals are diagnosed with, and treated for, , more resistance to second-line drugs is expected to emerge," explains Tracy Dalton, the study's lead author from the US Centers for Disease Control and Prevention (CDC). "So far, XDR TB has been reported in 77 countries worldwide, but exact prevalence remains unclear."

In the Preserving Effective Study (PETTS), Dalton and colleagues used population-based data to quantify the extent of XDR TB and identify for being infected with a strain resistant to second-line drugs among people with MDR TB from Estonia, Latvia, Peru, the Philippines, Russia, South Africa, South Korea, and Thailand.

Isolates from 1278 adults with MDR TB were shipped to the US CDC and tested for susceptibility to 11 first-line and second-line antituberculosis drugs.

The prevalence of resistance varied widely between countries. Overall, resistance to any second-line drug was detected in nearly 44% of patients, ranging from 33% in Thailand to 62% in Latvia. In a fifth of cases resistance to at least one second-line injectable drug was identified, ranging from 2% in the Philippines to 47% in Latvia. The proportion of cases with resistance to a fluoroquinolone was almost 13%, with the lowest prevalence in the Philippines (7%) and the highest in South Korea (32%).

XDR TB was detected in 6.7% patients overall, with prevalence in (15.2%) and Russia (11.3%) more than twice the current WHO global estimate, at 5.4%.

Among the study's other key findings were that risk of XDR disease was more than quadrupled in previously treated patients, and previous treatment with second-line drugs was consistently the strongest risk factor for resistance to these drugs.

Further analysis also found unemployment, a history of imprisonment, alcohol abuse, and smoking as factors associated with to second-line injectable drugs, suggesting that "social factors should be taken into account in the management of TB", says Dalton.

According to Dalton, "our country-specific results can be extrapolated to guide in-country policy for laboratory capacity and for designing effective treatment recommendations for MDR TB."

Commenting on the paper, Hoffner adds, "These results show that XDR TB is increasingly a cause for concern, especially in areas where prevalence of MDR TB is high. Nevertheless, information remains insufficient to give a clear view of the worldwide distribution and true magnitude of XDR TB. Updated information on MDR TB and investigation of the trends are urgently needed...especially since the true scale of the burden of MDR and XDR tuberculosis might be underestimated and seem to be rapidly increasing."

Explore further: Management of TB cases falls short of international standards

Related Stories

Management of TB cases falls short of international standards

February 9, 2012
The management of tuberculosis cases in the European Union (EU) is not meeting international standards, according to new research.

Improving detection of drug-resistant tuberculosis

May 2, 2012
(Medical Xpress) -- European researchers are developing new assays to detect drug resistant strains of Mycobacterium tuberculosis.

Recommended for you

Google searches can be used to track dengue in underdeveloped countries

July 20, 2017
An analytical tool that combines Google search data with government-provided clinical data can quickly and accurately track dengue fever in less-developed countries, according to new research published in PLOS Computational ...

MRSA emerged years before methicillin was even discovered

July 19, 2017
Methicillin resistant Staphylococcus aureus (MRSA) emerged long before the introduction of the antibiotic methicillin into clinical practice, according to a study published in the open access journal Genome Biology. It was ...

New test distinguishes Zika from similar viral infections

July 18, 2017
A new test is the best-to-date in differentiating Zika virus infections from infections caused by similar viruses. The antibody-based assay, developed by researchers at UC Berkeley and Humabs BioMed, a private biotechnology ...

'Superbugs' study reveals complex picture of E. coli bloodstream infections

July 18, 2017
The first large-scale genetic study of Escherichia coli (E. coli) cultured from patients with bloodstream infections in England showed that drug resistant 'superbugs' are not always out-competing other strains. Research by ...

Ebola virus can persist in monkeys that survived disease, even after symptoms disappear

July 17, 2017
Ebola virus infection can be detected in rhesus monkeys that survive the disease and no longer show symptoms, according to research published by Army scientists in today's online edition of the journal Nature Microbiology. ...

Mountain gorillas have herpes virus similar to that found in humans

July 13, 2017
Scientists from the University of California, Davis, have detected a herpes virus in wild mountain gorillas that is very similar to the Epstein-Barr virus in humans, according to a study published today in the journal Scientific ...

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.