Nearly a quarter of TB patients in the region carry strains that are resistant to drugs, a new study finds, which raises the possibility of a major public-health threat.
By Nathan Collins
A man suffering from tuberculosis lies in bed. (Photo: Andrew Renneisen/Getty Images)
Though Americans might think of tuberculosis as a thing of the past, it remains a leading (if declining) cause of death worldwide. But concern is growing about drug-resistant strains of the disease—and, according to a new study of TB in West Africa, those strains may be much more common than previously thought.
“West African drug-resistance prevalence poses a previously underestimated, yet serious public health threat, and our estimates obtained differ significantly from previous World Health Organisation (WHO) estimates,” writes an international team led by Medical Research Council Unit, The Gambia researchers Florian Gehre, Jacob Otu, and Lindsay Kendall. “Therefore, our data are reshaping current concepts and are essential in informing WHO and public health strategists to implement urgently needed surveillance and control interventions in West Africa.”
Although MRSA—short for methicillin-resistant Staphylococcus aureus—is probably the best known drug-resistant bacteria in the United States, plenty of other bacteria have developed defenses against standard antibiotics. Drug-resistant tuberculosis is a particularly nasty one: For the worst strains, known as extensively drug-resistant tuberculosis (XDR TB), medical care can cost nearly half a million dollars just to treat, never mind productivity losses and the personal toll it takes on patients and families. Even multi-drug-resistant TB (MDR TB), can be difficult and expensive to treat, since common TB drugs don’t work.
“West African drug-resistance prevalence poses a previously underestimated, yet serious public health threat.”
Imagine what a problem that could be in low-income countries like those in West Africa. Actually, until now you couldn’t do much better than imagine, in large part because adequate testing facilities are scarce, and no one was quite sure how common MDR and XDR were.
To remedy that problem, researchers at MRC Unit, The Gambia worked with laboratories from around the region for four years to improve clinical practices, with special emphasis on detecting drug-resistant tuberculosis strains. Those laboratories then collected a total of 974 usable samples from new and returning TB patients at nine testing sites in Burkina Faso, The Gambia, Ghana, Guinea-Bissau, Mali, Nigeria, Senegal, and Togo.
In all, 39 percent of those patients had a strain resistant to at least one first-line tuberculosis drug, and 22 percent had an MDR strain, technically defined as one that can’t be treated with the antibiotics rifampicin and isoniazid. As one might suspect, drug-resistant strains were more common in patients who’d been treated for TB in the past: Thirty-five percent of those who’d been treated previously had MDR TB, compared with just 6 percent of new patients.
The researchers found no signs of XDR TB, but they did find signs of “pre-XDR,” that is, strains that were resistant to some second-line tuberculosis drugs, in all of their study sites, including new patients in Ghana and Togo.
It’s possible those figures don’t reflect the true prevalence of MDR and pre-XDR strains in West Africa, since the study only considered patients who actually came in for testing—not necessarily a representative sample of West Africans sick with tuberculosis. Still, the researchers argue, their results “should already prompt the implementation of continuous surveillance of all re-treatment patients in participating countries.”
“[D]rug-resistant TB could become a serious public health problem in West Africa if required control measures are not taken,” the team writes.