Innovative Screening Method Finds Rifabutin Can Fight Acinetobacter baumannii Superbug

Researchers have discovered that an old antibiotic may be a powerful new tool against a deadly superbug, thanks to an innovative screening method that better mimics conditions inside the human body. The study was published in June in Nature Microbiology.

Rifabutin is used to treat TB, especially in people with HIV/AIDS who can't tolerate a similar drug, rifampin. It is on the World Health Organization's List of Essential Medicines, the safest and most effective medicines needed in a health system.

Until now, it hadn't been tried against Acinetobacter baumannii, which emerged during the Iraq War as a troop-killing superbug in military treatment facilities. Acinetobacter causes pneumonia, meningitis and bloodstream infections; it tends to strike patients requiring lengthy hospital stays and invasive devices like catheters and ventilators. Each year, Acinetobacter baumannii is responsible for around 2 percent of the 99,000 US deaths from hospital-acquired infections, according to the Centers for Disease Control and Prevention.

One reason rifabutin's ability to fight superbugs was overlooked is because of current screening techniques. Since the 1940s, new or existing antibiotics have been tested against bacteria grown in rich culture media. The researchers designed a new type of nutrient-limited media that better mimics conditions inside the body. They hypothesized that the more realistic media might unmask antibiotics with hidden strengths.

The researchers found that rifabutin was vigorously active against Acinetobacter baumannii grown in the nutrient-limited media but not effective against bacteria grown in the more commonly used media. The researchers say that rifabutin can be used immediately to treat such infections because it is already FDA-approved, cheap and generic, and on the market, but that randomized controlled human trials should still be conducted to prove its efficacy.