Antibiotics May Make ‘Superbug’ MRSA Stronger

The antibiotic most commonly used to treat MRSA may actually make the infection worse, a new study finds.

The bacterium Staphylococcus aureus — known to cause “staph” infections, a type of soft tissue bacterial infection — is a major public health threat, responsible for a growing number of serious illnesses and deaths.

In its antibiotic-resistant form, Methicillin-resistant Staphylococcus aureus, or MRSA, causes more than 80,000 infections and 11,000 deaths each year. While MRSA is resistant to many antibiotics, it does respond to others, and the infection is often treated with a combination of two or more antibiotics for this reason.

But the study, which appeared in the journal Cell Host & Microbe on Wednesday, finds that one of the most common antibiotics used to treat the infection may inadvertently activate the body’s own pathogen-defense system and worsen MRSA skin infections.

Dr. George Liu, a researcher at Cedars-Sinai Medical Center in Los Angeles and one of the study’s authors, said in a statement individuals infected with MRSA who receive a beta-lactam antibiotic — a broad class of medicines that includes penicillin derivatives — “could end up being sicker than if they received no treatment at all.”

“Our findings underscore the urgent need to improve awareness of MRSA and rapidly diagnose these infections to avoid prescribing antibiotics that could put patients’ lives at risk,” he said.

While the staph bacteria is often carried on the skin and in the noses of healthy people, MRSA colonizes roughly 1 percent of people. The typical treatment is beta-lactam. In the study on mice, the researchers tested the immune system’s response to those antibiotics.

The scientists gave a high number of MRSA bacteria to the mice, eliciting an infection. Then, they administered beta lactam antibiotics to treat the infection. That caused the mice to —> Read More