New target could weaken ‘nightmare bacteria’

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Researchers have discovered a new cellular target for weakening a daunting microbe that can become highly tolerant to a variety of antibiotics.

“We identified a new function important to antibiotic tolerance, which could be targeted to enhance the activity of our current antibiotics,” says lead study author Dao Nguyen, an associate professor of medicine at McGill University and a scientist from the Translational Research in Respiratory Diseases Program at the Research Institute of the McGill University Health Centre. “This is critical if we want to improve the efficacy of our antibiotics and prevent such treatments from failing.”

The lung infection microbe, Pseudomonas aeruginosa, is the leading cause of death for thousands of people living with cystic fibrosis. This bacterium also causes many other serious infections in people with weakened defenses and immune systems.

P. aeruginosa causes lifelong lung infections in individuals with cystic fibrosis, and these infections cannot be cleared, even by cocktails of the most potent antibiotics available,” says Nguyen, who is also a respirologist at the MUHC.

‘Nightmare bacteria’

The Centers for Disease Control and Prevention (CDC) in the United States has listed P. aeruginosa¬†among the “nightmare bacteria,” with an estimated 51,000 healthcare-associated infections each year resulting in around 400 deaths. It is a common cause of healthcare-associated infections such as pneumonia, bloodstream or urinary tract infections, and surgical site infections.

“Many bacteria, such as P. aeruginosa, when they grow slowly or do not grow at all, become tolerant to antibiotics,” explains first author Dorival Martins, a senior postdoctoral fellow in Nguyen’s lab.

“This is a crucial problem because many chronic infections are caused by bacteria that are slow growing or enter a dormant state when they reside in a living host, and this causes treatments to fail or infections to relapse in patients,” Martins says.

A key weakness

As reported in the in the Proceedings of the National Academy of Sciences, researchers discovered that when P. aeruginosa is under stress or lacking nutrients, it uses a stress signaling system and defense enzyme (superoxide dismutase) to modify its cell membrane, making it less permeable to molecules and preventing antibiotics from penetrating the cell.

Inhibition of the enzyme activity or the stress signaling system could render the pathogen more susceptible to antibiotics, the researchers say.

“Up until now antibiotic tolerance in slow growing bacteria was widely attributed to the fact that targets of antibiotics were not available or inactive in ‘dormant’ cells. With this research we have shown there is more to it than that,” Nguyen says.

“We identified a new link between the stress defense enzyme, the regulation of membrane permeability, and antibiotic tolerance. In the long run, the discovery of this promising cellular target could expand the utility of our antibiotics and make new ones more effective.”

Source: McGill University