Dr Deborah Williamson
Dr Deborah Williamson

20 September 2016

A topical cream containing antibiotics that is widely used for treating skin infections caused by staphylococcal (‘staph’) bacteria could have perversely contributed to New Zealand’s soaring rate of staph skin infections.

Fusidic acid is currently recommended as a first-line treatment for skin infections such as school sores (impetigo), the most common cause of which is the bacteria Staphylococcus aureus (S. aureus).

However, a Health Research Council of New Zealand (HRC)-funded study led by clinical microbiologist Dr Deborah Williamson has found high levels of fusidic acid resistance in S. aureus skin infections in New Zealand.

Dr Williamson says there has been a significant increase in the number of S. aureus infections in New Zealand over the past decade, with Māori and Pacific children particularly affected. New Zealand has a higher incidence of S. aureus infections than anywhere else in the developed world.

“The increase that we’ve seen in the incidence of serious skin infections in New Zealand children has happened at the same time as an increase in the dispensing of topical fusidic acid to treat skin infections,” says Dr Williamson.

“Coupled with this increased use of topical fusidic acid, we have also found a marked increase in fusidic acid resistance in S. aureus, both in Auckland and in a collection of S. aureus samples that were taken from around New Zealand. Since 1999 when we first measured this, fusidic acid resistance in New Zealand has almost doubled to approximately 30 per cent – that’s one of the highest rates in the developed world.”

Dr Williamson, who carried out this study for her PhD as part of a HRC Clinical Research Training Fellowship at the University of Auckland, is now Deputy Director of the Microbiological Diagnostic Unit – Public Health Laboratory at the University of Melbourne in Australia.

She says in the face of such high levels of resistance it is “highly questionable whether fusidic acid should continue to be recommended as a first-line topical agent for school sores”.

In addition to urgent regulatory interventions on the use of fusidic acid in New Zealand, Dr Williamson says clinical trials are needed to assess the effectiveness of alternative compounds, such as antiseptic agents, in treating school sores.

“Some people think that topical antibiotic creams aren’t as big an issue when it comes to antibiotic resistance as antibiotics in tablet form because you apply it to the skin, but these topical antibiotics kill or inhibit bacteria in the same way as tablets. We have extremely strong evidence now to show that New Zealand needs to take a hard line on the use of topical antibiotics,” says Dr Williamson.

HRC Chief Executive Professor Kath McPherson says this important study is a stark example of how well-intentioned responses to a significant public health problem – such as prescribing antibacterial agents at high rates to counter an epidemic of S. aureus skin infections in New Zealand – can have major unintended consequences.

“Antibacterial resistance threatens the effective prevention and treatment of an ever-increasing range of infections caused by bacteria, parasites, viruses and fungi. The recent final ruling by the FDA in the US to ban the marketing of antibiotic hand and body wash products that contain certain specific antibacterial ingredients shows just how seriously we need to treat this very real threat to global public health,” says Professor McPherson.

As a result of her work on this HRC-funded study, Dr Williamson has received a Mardsen Fund grant with Professor Gregory Cook (University of Otago, Dunedin) to research how antiseptics can influence antibiotic resistance, and potentially identify ways to limit the spread of resistant S. aureus.