A new study shows that misuse of a class of antibiotic drugs called
fluoroquinolones is creating drug-resistant strains of tuberculosis, or
TB, a bacterial respiratory disease that the World Health Organization
says kills two million people worldwide each year. The finding dims
hopes that the drug could be used more widely to treat this deadly
Overreliance on certain antibiotics
Although TB is curable, treatment requires at least six months of continuous therapy using several drugs at once. Researchers have been hopeful that fluoroquinolones could help change that.
But Rose Devasia, an infectious disease researcher at Vanderbilt University, says the effectiveness of these safe, easy-to-take drugs has led to widespread overprescribing for a range of illnesses, sometimes even before it's known what kind of infection is being treated.
That, says Devasia, can cause problems when patients actually have tuberculosis. "Say they go to an emergency room and they have a cough. The physician thinks, 'Oh, it's probably pneumonia. I'm going to give him a fluoroquinolone.' The fluoroquinolone partially [treats] the TB. He feels good for about 10, 12, 13 days, but then the cough comes back," she says.
"So he goes to another physician or he goes back to another emergency room. He says, 'I've got this cough.' He gets another course of fluoroquinolones." Devasia says each time a patient with undiagnosed tuberculosis is treated for the wrong disease using fluoroquinolones, it increases the risk that he'll develop fluoroquinolone-resistant TB.
Researching the connection between TB and fluoroquinolones
In a study published in the American Journal of Respiratory and Critical Care Medicine, Devasia and her colleagues found that nearly one in five tuberculosis patients had received fluoroquinolones in the year before they were diagnosed with TB.
A typical course of fluoroquinolones is about 10 days. For every additional ten days a patient took the medications, the odds of developing fluoroquinolone-resistant TB increased by 50 percent.
In many developing-world pharmacies, fluoroquinolones are easily available without a prescription, under names such as Cipro and Levaquin, and they're used to treat everything from diarrhea to pneumonia.
Devasia says the results of her study make her hesitant to support using fluoroquinolones as the first choice against TB. She prefers to save them for cases when the usual first-line drugs fail.
Neel Ghandi, assistant professor at the Albert Einstein College of Medicine says, "To some degree, to me the message from this article is that we need to reconsider how we use fluoroquinolones generally."
He says when you're not sure why a patient is sick, fluoroquinolones may be fairly safe and easy to use. But, he says, emerging drug resistance demonstrates the consequences of misuse. Ghandi says there are very few effective drugs to treat TB, and it will be at least five to 10 years before any new drugs are available.
"The fluoroquinolones are our next hope in terms of really modifying TB care," says Ghandi. "And when you see resistance emerge the way it has in this article, I think it is a good reason to pause and say, 'Perhaps we need to re-evaluate how we're using these medications.'"
Ghandi notes that the study was done in the United States, where better tools are available to diagnose diseases. He says many more resources need to be invested in diagnostics capabilities in the developing world so doctors there can identify and treat patients for the right disease and save fluoroquinolones for when they're truly needed. Study author Devasia is working on a way to cut the time it takes to diagnose resistant TB from weeks to hours.