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Certain antibiotics can make the superbug, methicillin-resistant Staphylococcus aureus (MRSA), even stronger, a new study found.

MRSA is a major public health concern due to the fact that it has become very difficult to treat and according to a new study, treatment for MRSA skin infections might be getting even scarcer. For this study, researchers examined the effects of using first-line antibiotics - beta-lactam antibiotics (i.e. penicillin, amoxicillin and carbapenem) - on MRSA skin infections in rats.

The researchers found that this class of antibiotics appeared to make the skin condition worse.

"We now have evidence that the very factor that defines certain S. aureus as MRSA is a factor that can also make MRSA more pathogenic," study author Sabrina Muller of Cedars-Sinai Medical Center said reported in the press release. "However, this pathogenic factor is not unleashed unless MRSA is exposed to beta-lactam antibiotics. Therefore, a poor choice of antibiotic can make MRSA infection worse compared to no treatment."

The researchers first examined the structural makeup of MRSA and found that unlike normal S. aureus, MRSA can bypass the effects of beta-lactam antibiotics. These antibiotics kill regular S. aureus by inactivating the enzymes responsible for cell wall synthesis. In MRSA, however, an enzyme known as PBP2A does not become inactivated in the presence of beta-lactam antibiotics.

Instead, the superbug continues to build strong cell walls that are different from those seen in normal staph infections. These walls trigger the body's immune system, which leads to more inflammation that causes the infection to worsen.

"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," co-senior study author George Liu of Cedars-Sinai Medical Center said.

The researchers hope that their study's findings will help doctors make safer medical decisions when it comes to treating MRSA skin infections. However, since the study was conducted in rats, the researchers stated that they have to now collect human data in order to determine the effects of beta-lactam antibiotics on human cases.

Co-senior study author David Underhill of Cedars-Sinai Medical Center added, "The obvious next step is to verify whether this occurs in humans. If human data suggest that beta-lactam antibiotics given alone could make MRSA infection worse, then we may need to rethink whether beta lactams should be our first choice of empiric antibiotic before the source of the infection is known, especially in case of severe infections."

The study's findings were published in Cell Host & Microbe.