Azithromycin — a common antibiotic sold commercially as Zithromax Z-Pak — can effectively kill several multidrug-resistant bacteria, according to a study published in EBioMedicine.
Azithromycin is the most often prescribed antibiotic in the United Sates, and is used to treat common infections like strep throat and sinusitis. However, it is not given to patients with infections caused by MDROs, because several lab tests in laboratory media, or the "nutrient broth" that helps bacteria grow, concluded that it doesn't effectively kill those bacteria.
This study, conducted by researchers at University of California, San Diego School of Medicine and Skaggs School of Pharmacy and Pharmaceutical Sciences, tested the antibiotic under conditions that more closely resemble the human body and its natural antimicrobial factors. The researchers tested azithromycin's effectiveness against three bacteria: Pseudomonas aeruginosa, Klebsiella pneumoniae and Acinetobacter baumannii.
The study found that the antibiotic, when tested in the more realistic conditions, was effective against these MDROs, especially when paired with another antibiotic, colistin.
Researchers also tested azithromycin on a mouse model of multidrug-resistant A. baumanni pneumonia, and found that 24 hours after infection, the mice treated with azithromycin had 99 percent fewer bacteria in their lungs than mice who did not receive treatment.
The study's authors recommend researchers take a more holistic approach to testing antibiotics that considers the bacteria and the patients' immune system.
"If something this simple could be overlooked for so many years, what else might we be missing?" asked Victor Nizet, MD, the study's lead author.