Dr. Max Salfinger examines ways laboratories can speed tuberculosis diagnosis

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The bacterium that causes tuberculosis (TB)—a life-threatening respiratory condition spread from person to person through infected particles in the air—takes weeks-to-months to grow, making it one of nature’s slowest-growing infections. That means a patient with suspected but unconfirmed tuberculosis can remain undiagnosed, untreated, and infectious while a laboratory grows a culture with the slow-to-replicate bacterium. Time ticks while people remain sick and contagious before an effective antibiotic is prescribed.

So what’s the key to faster diagnosis?

Dr. Max Salfinger, a USF College of Public Health (COPH) professor specializing in global health, is the coauthor of the paper “How Can the Tuberculosis Laboratory Aid in the Patient-Centered Diagnosis and Management of Tuberculosis?” The paper was published in the journal Clinics in Chest Medicine in December 2019.

Max Salfinger, MD. (Photo courtesy of Dr. Salfinger)

Mycobacterium tuberculosis replicates in 20 hours versus the 20 minutes it takes for common bacteria such as Staphylococcus aureus or Escherichia coli,” said Salfinger. “In the laboratory, this means instead of incubating the culture for one to two days, it takes weeks or even months for a culture to grow colonies of bacteria visible to the naked eye.  When laboratories adopt rapid molecular detection methods, such as nucleic acid amplification [a sensitive, rapid diagnostic test that can be performed directly on a respiratory sample and can detect small numbers of bacteria by looking for the DNA], reporting is faster, with reporting of positive results in just hours. When antibiotic-resistance testing is also rapid, patient treatment can be adjusted sooner if needed, which in turn leads to a more accurate treatment regimen.”

If better, faster testing is available, why aren’t laboratories using it? “The problem,” says Salfinger, “is twofold.”

While tests like nucleic acid amplification have been around for 20-plus years, laboratories may be slow to embrace it because of its cost to the laboratory and the additional skills, equipment and facility requirements needed to properly perform the tests.

But Salfinger points to the big picture.

“Rapid detection of TB in a patient decreases the cost to the entire health system and to the well-being of the patient. It really should be a no-brainer,” he said. “With rapid reporting, patients are started on therapy sooner, and if antibiotic-resistance testing is provided rapidly as well, the drug regimen can be customized as needed. This leads to a more rapid cure of the patient—drug-susceptible TB treatment takes months, drug-resistant TB even longer—and decreased time the patient is sick and able to infect others.”

Mycobacterium tuberculosis. (Google Images)

According to the World Health Organization (WHO), TB affected 10 million people worldwide in 2018 and nearly 500,000 cases were resistant to the antibiotic most commonly used to treat the disease. WHO has called multi-drug-resistant TB a “public health crisis and health security threat.”  By 2030, it hopes to see a 90 percent reduction in deaths and an 80 percent reduction in TB incidence rates compared to 2015.

To help ease the crisis, Salfinger sees the need for simpler, more affordable nonsputum TB tests (for example, tests that look at blood, urine or even oral swabs instead of mucus) that detect TB markers. Better individualized management, follow-up and monitoring of TB patients is also key, he notes.

“Once a patient has drug resistance, the TB disease becomes much more difficult for the patient to treat and much more expensive. In resource poor countries, this can be devastating,” he commented.

Story by Donna Campisano, USF College of Public Health