Australian researchers have identified a new superbug in hospitals that is capable of causing near-untreatable infections.

Multidrug-resistant Staphylococcus epidermidis (S. epidermidis) is a leading cause of hospital-acquired infections, but far less is known about this organism than its cousin, methicillin-resistant Staphylococcus aureus (MRSA).

S. epidermidis is found on the skin of all humans, and is frequently dismissed as a false positive result in diagnostic samples.

Researchers in Melbourne have looked at hundreds of S. epidermidis isolates from 78 institutions in 10 countries around the world, and found three strain sub-types that have spread globally and are resistant to nearly all antibiotics.

S.epidermidis appears to have made a small change in its DNA that led to resistance to two major antibiotics, while some of the strains discovered in Europe are resistant to all known antibiotics.

“These two antibiotics are unrelated and you would not expect one mutation to cause both antibiotics to fail,” said lead researcher Dr Jean Lee.

“Our study suggests current guidelines for treating these infections with the combination of these two antibiotics that were thought to protect one another against developing resistance are based on an incorrect assumption, and that current treatment recommendations need to be reviewed.”

S. epidermidis infects people who are immunocompromised or have had prosthetic materials implanted, such as catheters and joint replacements.

The researchers suggest the reason for the spread of these S. epidermidis strains is likely two-fold.

Firstly, catheters and other implanted devices are frequently impregnated with antibiotics as a strategy to prevent infection, however this approach is likely promoting the development of resistance.

Secondly, these infections are most prevalent in intensive care, where patients are sickest and strong antibiotics liberally prescribed, promoting the development of additional resistance.

University of Melbourne’s Professor Ben Howden said the extent of the spread of these antibiotic-resistant strains highlights a growing problem in hospitals around the world.

“There is an urgent need for an international monitoring system to understand the prevalence and impact of S. epidermidis and to systematically measure antibiotic resistance and infections due to this pathogen,” he said.

“We need a better understanding of how S. epidermidis is persisting in hospitals, because it’s happening in an era where MRSA is disappearing through good infection control measures,” Professor Howden said.

The full study is accessible here.