Staph Infection Antibiotics Can Make MRSA Patients Sicker

Antibiotics commonly used to kill normal staph infections can actually increase deadly methicillin-resistant Staphylococcus aureus (MRSA) bacteria resistance.

MRSA, a type of staph infection resistant to many antibiotics, can cause serious problems and even become life-threatening. Just in October, New York Giants tight end Daniel Fells nearly lost his foot due to the infection. Now researchers from Cedars-Sinai Medical Center found that the superbug can become even more resistant when treated with a certain type of antibiotics.

“It is one of the biggest antibiotic-resistant pathogens in the US,” co-senior author George Liu, MD, PhD, said in a news release.

When the team treated MRSA-infected mice with beta lactams (antibiotics similar to methicillin), the bacteria grew cell walls that were very inflammatory and harmful to tissues. Interestingly, beta lactams are used to treat normal staph infections, yet in MRSA-specific cases they have the opposite effect. The antibiotics inactivate the enzymes which construct the cell walls; however, when MRSA is exposed to beta lactams, one of the enzymes, PBP2A, is not inactivated. Therefore, MRSA is able to continue building cell walls. The authors also found that the cell walls are different than those in normal staph infections.

“This altered cell wall induces a powerful inflammatory response,” explained co-senior author David Underhill, PhD. “In mice infected with MRSA, induction of PBP2A with methicillin led to more inflammation and pathology.”

MRSA’s antibiotic resistance correlates with inflammatory responses, described in Cell Host & Microbe. The mice became even sicker when treated with beta lactams, which indicates that the same could happen in humans.

“Based on this research, clinical studies are warranted,” said one of the authors Sabrina Mueller, PhD. “However, pending the outcome of those studies, physicians should follow current national guidelines set by the Infectious Diseases Society of America for antimicrobial treatment of staph infections.”

The researchers stressed that these findings are based off of mice models and need to be investigated in humans.

“There is much work ahead of us before we can make a firm recommendation about the advantages or disadvantages of treatment with beta-lactam antibiotics,” Liu concluded.

There are more than 11,000 deaths each year from MRSA, according to the Centers for Disease Control and Prevention (CDC), and lifestyle choices such as smoking cigarettes increases the bacteria’s resistance.