Long ignored as a treatment option for certain serious bacterial infections, azithromycin proves strikingly effective in new lab and animal tests
Contrary to current medical dogma, researchers at University of California, San Diego School of Medicine and Skaggs School of Pharmacy and Pharmaceutical Sciences report that the common antibiotic azithromycin kills many multidrug-resistant bacteria very effectively -- when tested under conditions that closely resemble the human body and its natural antimicrobial factors.
The researchers believe the finding, published June 10 by EBioMedicine, could prompt an immediate review of the current standard of care for patients with certain so-called "superbug" infections.
Azithromycin is the most often prescribed antibiotic in the United States, where short courses can cure common bacterial infections such as strep throat and sinusitis. But azithromycin, also sold commercially as Zithromax Z-Pak, is never given to patients with some of the most nefarious multidrug-resistant bacterial infections. That's because years of testing in standard laboratory media -- the nutrient broth that helps bacteria grow -- concluded that azithromycin doesn't kill these types of bacteria.
"Unquestioning adherence to a single standardized lab practice may be keeping doctors from considering potentially life-saving antibiotics -- therapies that are proven safe and readily available in any hospital or pharmacy," said senior author Victor Nizet, MD, professor of pediatrics and pharmacy. "While bacterial agars and testing media are useful in providing consistency for hospital laboratories around the world, the actual infection is taking place in the blood and tissues of the patient, and we know the action and potency of drugs can change quite dramatically in different surroundings."
The bacteria at the center of this study are Gram-negative rods, so-called due to their cell wall structure (they appear "negative" in a classic typing test known as the Gram stain) and their shape. Nizet's team studied extremely antibiotic-resistant strains of three medically important Gram-negative rods: Pseudomonas aeruginosa, Klebsiella pneumoniae and Acinetobacter baumannii.
These opportunistic pathogens rarely infect healthy people but instead strike debilitated patients in hospitals, such as those with weakened immune systems, or following trauma or surgery, sometimes with deadly consequences. The Centers for Disease Control and World Health Organization have warned that resistance is rapidly spreading in these species, and no new antibiotic candidates are on the horizon.
In this study, Nizet's team found that simply growing these Gram-negative rod bacteria in mammalian tissue culture media -- the same stuff used to sustain human cells in the lab -- instead of standard bacteriologic media made a huge difference in their sensitivity to azithromycin. Even more striking, the drug-resistant superbugs were completely wiped out when azithromycin was paired with the antibiotic colistin or with antimicrobial peptides produced naturally by the human body during infection.
To test these promising laboratory results in a live infection system, Nizet and team moved the experiment into a mouse model of multidrug-resistant A. baumannii pneumonia. They treated the mice with a single injected dose of azithromycin at a concentration that mimics the amount typically given by IV to human patients. Twenty-four hours after infection, azithromycin-treated mice had 99 percent fewer bacteria in their lungs than untreated mice. Similarly, in mouse models of multidrug-resistant P. aeruginosa and K. pneumoniae infections, a single dose of azithromycin reduced bacterial counts by more than 10-fold.
According to the authors, the study suggests that the general effectiveness of antibiotics in the decades since the discovery of penicillin has led to complacency in our approach to antibiotic evaluation. In the current era of ever-increasing antibiotic resistance, they recommend a more holistic approach that considers both the bug and the patient's immune system.
"If something this simple could be overlooked for so many years, what else might we be missing?" Nizet said.
Co-authors of this study (DOI 10.1016/j.ebiom.2015.05.021) also include Leo Lin, Poochit Nonejuie, Jason Munguia, Andrew Hollands, Joshua Olson, Quang Dam, Monika Kumaraswamy, Heriberto Rivera, Ross Corriden, Mary E. Hensler, Michael D. Burkart, Joe Pogliano, and George Sakoulas, UC San Diego; and Manfred Rohde, Helmhotz Centre for Infection Research, Germany.
This research was funded, in part, by the National Institutes of Health (grants HD071600, AI057153 AI052453, AR052728 and GM073898).
Heather Buschman | EurekAlert!
Study suggests possible new target for treating and preventing Alzheimer's
02.12.2016 | Oregon Health & Science University
The first analysis of Ewing's sarcoma methyloma opens doors to new treatments
01.12.2016 | IDIBELL-Bellvitge Biomedical Research Institute
A multi-institutional research collaboration has created a novel approach for fabricating three-dimensional micro-optics through the shape-defined formation of porous silicon (PSi), with broad impacts in integrated optoelectronics, imaging, and photovoltaics.
Working with colleagues at Stanford and The Dow Chemical Company, researchers at the University of Illinois at Urbana-Champaign fabricated 3-D birefringent...
In experiments with magnetic atoms conducted at extremely low temperatures, scientists have demonstrated a unique phase of matter: The atoms form a new type of quantum liquid or quantum droplet state. These so called quantum droplets may preserve their form in absence of external confinement because of quantum effects. The joint team of experimental physicists from Innsbruck and theoretical physicists from Hannover report on their findings in the journal Physical Review X.
“Our Quantum droplets are in the gas phase but they still drop like a rock,” explains experimental physicist Francesca Ferlaino when talking about the...
The Max Planck Institute for Physics (MPP) is opening up a new research field. A workshop from November 21 - 22, 2016 will mark the start of activities for an innovative axion experiment. Axions are still only purely hypothetical particles. Their detection could solve two fundamental problems in particle physics: What dark matter consists of and why it has not yet been possible to directly observe a CP violation for the strong interaction.
The “MADMAX” project is the MPP’s commitment to axion research. Axions are so far only a theoretical prediction and are difficult to detect: on the one hand,...
Broadband rotational spectroscopy unravels structural reshaping of isolated molecules in the gas phase to accommodate water
In two recent publications in the Journal of Chemical Physics and in the Journal of Physical Chemistry Letters, researchers around Melanie Schnell from the Max...
The efficiency of power electronic systems is not solely dependent on electrical efficiency but also on weight, for example, in mobile systems. When the weight of relevant components and devices in airplanes, for instance, is reduced, fuel savings can be achieved and correspondingly greenhouse gas emissions decreased. New materials and components based on gallium nitride (GaN) can help to reduce weight and increase the efficiency. With these new materials, power electronic switches can be operated at higher switching frequency, resulting in higher power density and lower material costs.
Researchers at the Fraunhofer Institute for Solar Energy Systems ISE together with partners have investigated how these materials can be used to make power...
16.11.2016 | Event News
01.11.2016 | Event News
14.10.2016 | Event News
02.12.2016 | Medical Engineering
02.12.2016 | Agricultural and Forestry Science
02.12.2016 | Physics and Astronomy