Local infectious disease experts are working with their overseas counterparts to tackle one of the most resilient hospital superbugs.

The scourge of hospitals the world over, methicillin-resistant staphylococcus aureus, better known as MRSA, can cause oozing sores that take weeks to heal.

As the name suggests, the bacterium quickly develops a resistance to most antibiotics, making such infections tough to treat. Rather than developing a new drug, the experts from four countries will be testing a combination of two existing drugs that have shown promise in small-scale trials.

"The pharmaceutical industry's interest in this area is declining," said Dr David Lye, a senior consultant in Tan Tock Seng Hospital's (TTSH) infectious diseases department. "And new drugs are not proven to be better, but they are definitely more expensive."

While a daily dose of the current standard treatment - a drug called vancomycin - costs around $8, newer drugs can cost several hundred dollars a day.

For the trial, doctors will recruit 440 patients over a four-year period to see how well vancomycin and cloxacillin - another "old" antibiotic - work to purge MRSA from the blood.

This combination is estimated to cost $30 a day, but those who take part in the trial will get the medicine for free.

Singapore is in charge of recruiting half the patients, while the other three countries - Australia, New Zealand and Israel - will recruit the rest. TTSH will lead the local portion of the trial and the Singapore General Hospital and National University Hospital will also come on board.

Staphylococcus aureus is a common bacterium found on the skin or in the nose of three in 10 people without causing harm. Infections start when the bacteria enters the bloodstream through breaks in the skin, such from intravenous lines in hospitals.

"Patients who need kidney dialysis, those in intensive care, and cancer patients often need these (intravenous) lines," said Associate Professor Steven Tong of the Menzies School of Health Research in Australia.

According to the Health Ministry, the number of MRSA blood infections here stayed stable at about 0.89 case per 1,000 patient days between 2011 and 2014.