JCM Accepts, published online ahead of print on 17 June 2009

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J. Clin. Microbiol. doi:10.1128/JCM.02316-08
Copyright (c) 2009, American Society for Microbiology and/or the Listed Authors/Institutions. All Rights Reserved.

The in vitro effect of ultrasound on bacteria and a suggested protocol for sonication and diagnosis of prosthetic infections

Tor Monsen^*, Elisabeth Lövgren, Micael Widerström, and Lars Wallinder

Department of Clinical Bacteriology and Department of Orthopedics, University Hospital of Umeå, SE-90185 Umeå, Sweden; Department of Infectious Diseases, Hospital of Östersund, SE-83183 Östersund, Sweden; Department of Medical Microbiology, St. Olavs University Hospital and Institute of Laboratory Medicine, Children's and Women's Health, Norwegian University of Science and Technology, Trondheim, Norway

^* To whom correspondence should be addressed. Email: tor.monsen{at}climi.umu.se.

Sonication of implants has been shown to be a promising method for diagnosis of prosthetic infections due to its improved sensitivity, simplicity and low cost. The aim of the present study was to evaluate the effect of ultrasound performed during different conditions regarding temperature, duration and composition of sonication tubes on bacterial species often associated with prosthetic infections.

We found that ultrasound had an inhibitory effect on bacteria of which Gram-negative bacteria and in particular E. coli were almost eradicated after 5 minutes of sonication at 35°C. Gram-positive bacteria were found to be resistant to the effect of ultrasound.

Four factors were important for the inhibitory effect of sonication; the type of microorganism, temperature of the sonication buffer, time of exposure to ultrasound (minutes) and the material and composition of sonication tube in which sonication is performed.

Based on the results from the present study we propose a protocol for sonication and recovery of bacteria associated with biofilm on infected implants prior to conventional culture. From the present protocol we recommend sonication for 7 minutes at 22°C at maximum effect which permit survival of Gram-negative bacteria.