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Multidrug-resistant Tuberculosis More Widespread in Western Africa Than Previously Thought

NOV 13, 2016 | EINAV KEET
A new study from researchers in Africa and the United Kingdom has found that multidrug-resistant tuberculosis (TB) superbugs are more prevalent and widespread in Western Africa than previous estimates had suggested.

The World Health Organization (WHO) lists TB infections as one of the top 10 killers around the world, causing more than 10.4 million illnesses and 1.8 million deaths in 2015 alone. This deadly condition is caused by Mycobacterium tuberculosis bacteria, which most commonly attack the lungs, causing potentially severe infections. An active TB infection is typically marked by a bad cough, chest pains, and the coughing up of lung phlegm or blood, according to the Centers for Disease Control and Prevention (CDC). WHO officials note that people are much more likely to die of TB in low- and middle-income countries, which accounts for more than 95% of all TB-related deaths; TB patients in India, Indonesia, China, Nigeria, Pakistan, and South Africa together make up about 60% of all TB cases.

The rise of multidrug-resistant TB (MDR-TB) has been a growing concern to public health experts due to the fact that, like other antibiotic-resistant pathogens, it causes more virulent and hard-to-treat lung infections that are more likely to result in a patient’s death. Strains of TB that are resistant to the two antibiotic drugs – isoniazid and rifampin –  regarded as the best treatment for TB infections, have caused rising concern in places that have been hit the hardest by TB. In addition, rare, but even more dangerous, extensively drug-resistant TB (XDR TB) strains have also developed resistance to fluoroquinolone antibiotics, along with a resistance to injectable antibiotic treatments used as a second line of attack against the infections. WHO estimates that 480,000 people developed MDR-TB in 2015, and the treatment regimen can take up to two years or longer to clear the infection. About 9.5% of MDR-TB cases had XDR-TB in 2015.

Researchers from the Medical Research Council Unit in The Gambia and from the University of Warwick in the UK recently studied the prevalence of drug-resistant TB in West Africa, where the research team noted that the full extent of the superbug was previously unknown. The region includes 15 countries that are home to a total of 245 million people as well as high rates of TB, malaria, meningitis, and HIV/AIDS. The study looked to assess the scope of drug-resistant TB cases in nine study sites in eight countries – Burkina Faso, The Gambia, Ghana, Guinea-Bissau, Mali, Nigeria, Senegal, and Togo – where previous surveillance was limited. Doctors on the team collected TB isolates from 2009 to 2013 and conducted drug susceptibility tests on 974 samples to check for resistance to first- and second-line antibiotics. Their research findings were recently published in the journal BMC Medicine.

The study team identified MRD-TB isolates at all nine sites, and found that 39% of all the isolates that had been tested showed resistance to at least one first-line drug, while 22% were multidrug-resistant. In patients going through retreatment for cases not cleared by a previous treatment regimen, the researchers found that TB bacteria were more than four times more likely to be resistant than the isolates from new patients. In Mali, 59% of retreatment patients had MDR-TB, while in the two Nigeria sites, the rate was 39% (Ibadan) and 66% (Lagos).

In a press release, study author and investigator Martin Antonio, PhD, explained the significance of the team’s findings. “To our surprise, we found that multidrug-resistant and pre-extensively drug-resistant tuberculosis strains are already widely circulating and that drug resistance is a much bigger problem in West Africa than previously anticipated,” said Dr. Antonio. “WHO estimates the prevalence of multidrug resistance in new and retreatment cases to be 2% and 17% respectively but we found that it is 6% and 35% respectively.”

Filling in these holes of data, where little is known about the full extent of the drug-resistant TB problem, is an important part of stemming the epidemic, according to Dr. Antonio. “We recommend that efforts be put in place for containment of a potential West African TB epidemic at the earliest possible stage. This is especially important as West Africa with its 245 million inhabitants is one of the poorest regions globally, whose fragile health systems can easily be overwhelmed by infectious disease epidemics, as seen in the recent Ebola outbreak.”
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