In the fight against deadly antibiotic-resistant bacteria, UC San Diego researchers have unexpectedly discovered a potential new weapon: an extremely common antibiotic now believed ineffective.
The antibiotic is azithromycin, sold under the name Zithromax Z-Pak. The single most commonly used antibiotic in the United States, it’s prescribed for pneumonia, skin and throat infections. But it’s never even been tried against the multidrug-resistant superbugs. That’s because it shows no efficacy in standard lab tests.
But when researchers under the leadership of Dr. Victor Nizet tested the drug under conditions more closely resembling those of the human body, the antibiotic potently killed resistant strains of Pseudomonas aeruginosa, Klebsiella pneumoniae and Acinetobacter baumannii, These belong to a group of bacteria classified as Gram-negative rods, that have recently produced superbug strains,
Since azithromycin is already approved, it can be used immediately to treat superbug infections, said Nizet, a professor of pediatrics and pharmacy at UCSD. The study was published Wednesday in the journal EBioMedicine. Nizet was senior author. Leo Lin, also of UCSD, was first author.
Each year, at least 2 million Americans contract serious infections with antibiotic-resistant bacteria, according to a 2013 report from the U.S. Centers for Disease Control and Prevention. At least 23,000 die as a direct result of infection, more die as an indirect result of complications.
Meanwhile, the pharmaceutical industry has been developing more antibiotics, trying to keep from falling behind as once-useful drugs are rendered ineffective by new strains of bacteria. San Diego companies working on new antibiotics included Trius Therapeutics, purchased in 2013 along with Optimer Pharmaceuticals, which used to be based in San Diego.
Superbugs are especially dangerous in hospitals, where they infect patients with weakened immune systems or otherwise vulnerable. In February, UCLA Ronald Reagan Medical Center said two patients had died and five others infected from a superbug infection transmitted by improperly sterilized endoscopes.
Nizet has worked on the antibiotic resistance problem for years, including older superbugs such as MRSA, or methicillin-resistant Staphylococcus aureus. He observed the same phenomenon as well.
“It comes on the heels of our working on similar questions with other drug-resistant pathogens like MRSA, where we saw some of the antibiotics that did not have activity in the classical testing, actually worked very well when you combined them with the natural antibiotics from your immune system,” said Nizet, a professor of pediatrics and pharmacy at UCSD.
In the new study, researchers test azithromycin on drug-resistant bacteria growing in mammalian tissue cultures, which produce antibiotic chemicals naturally present in the body. They also tested the antibiotic in live mice. The treated mice experienced a 99 percent drop in multidrug-resistant A. baumannii pneumonia compared to untreated mice.
(Click here to read the full article, written by Bradley J. Fikes, SD Union Tribune)