More and more people are fitted with artificial knees, hips and other implants, but many end up with chronic infections as a result of the implants. For some of these patients, even long-term treatment with antibiotics proves totally ineffective. However, new research now raises hope for more effective treatment.

2013.09.05 | Mette Louise Ohana

A staphylococcus biofilm on the surface of an implant.

Knees, elbows, hips, coronary arteries and heart valves – the array of worn-out body parts which can be replaced by doctors today is extensive. And large is the number of patients with one or more implants, and never before has the population been as mobile as it is today.

There is, however, a downside to this otherwise happy story.

"When inserting a foreign object like an artificial hip in the body, this object, unfortunately, risks being colonised by bacteria capable of forming a so-called biofilm on the artificial surface. This occurs in 1-2% of the approx. 16,000 Danes undergoing bone replacement surgery each year. And this type of infection is often very difficult to treat," says Nis Pedersen Jørgensen, a PhD student at Aarhus University and medical doctor at Aarhus University Hospital.

Antibiotics normally kill bacteria such as staphylococci. And when testing bacteria from a biofilm infection using routine methods, the test result will most often show that the infection can be treated as usual. However, in an experiment, researchers have now for the first time tested the effect of different antibiotics on biofilm infections in mice, revealing that the effect of antibiotics is dramatically reduced. 

"We can see that far higher doses of antibiotics are needed to ensure the efficacy of the treatment – up to a thousand times higher, which, of course, is far more than you can administer to a patient. So, in these cases it would be better to begin by replacing the implant," says Nis Pedersen Jørgensen.

Hope for more effective treatment

The current study helps shed light on cases where patients with serious chronic infections cannot be cured despite long-term treatment with antibiotics and thus end up having to undergo surgery again.

"The method we have studied needs to be refined before it can be used for routine testing. Nevertheless, the preliminary results indicate that this will provide us with a better tool for assessing which patients can be treated with antibiotics. Hopefully, we will also be able to reduce the treatment time for patients whose only option is surgery. This will also reduce the costs of treating biofilm infections considerably," says Nis Pedersen Jørgensen.

No figures are available for Danish patients, but in the USA there are an estimated 17 million new cases of biofilm infections every year and at least 550,000 deaths.

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About biofilms

• Biofilms consist of bacteria growing in slime-enclosed aggregates
• The bacterial cluster acts as a shield against antibiotics, in which only the outermost bacteria are attacked
• Biofilms are usually not caused by poor hygiene during surgery, but rather a subsequent infection
• Biofilm infections are both difficult to diagnose and treat
• The new method measures the effect of different types of antibiotics on bacteria in biofilms

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Further information

Nis Pedersen Jørgensen, PhD student and medical doctor
Aarhus University, Department of Clinical Medicine and Aarhus University Hospital, Department of Infectious Diseases
Mobile: +45 2537 2055
nisjoe@rm.dk