It’s called MRSA, and it kills 20,000 people per year in the United States — and antibiotics may be making it even worse.

A new study indicates that what are known as beta-lactam antibiotics, a class that covers penicillin, cephalexin, and carbapenems, is making so-called “golden staph” worse by helping it become more resistant to drugs, according to a report by The Australian.

MRSA is a very deadly infection that is a problem for hospitals, where it kills one third of those who come down with it, which comes out to about 20,000 deaths each year in the U.S. alone and costs the health system $40 billion annually. Now, a new study in the journal Cell Host & Microbe finds that antibiotics are doing what scientists have long feared: turning it into a superbug by helping it develop a resistance to drugs.

The new study indicated that beta-lactam antibiotics were successfully degrading the cell walls of the MRSA bacteria, but it also resulted in the activation of immune cells in mice that resulted in worse inflammation and skin infections in mice. It means that for some patients, if they got treatment from antibiotics, the cure might be worse than the disease.

The study came about in the wake of a discovery by Chinese scientists that antibiotics appeared to be actually increasing the risk of heart attack. They noticed a small but “statistically significant” increase in risk of sudden cardiac death in patients that took macrolides, which are often prescribed for bacterial infections of a number of diseases. A total of 192 heart-related deaths per million courses of treatment were found in these patients.