Sonication is superior to scraping for retrieval of bacteria in biofilm on titanium and steel surfaces in vitro.
OBJECTIVE
Low-virulence implant infections are characterized by bacterial colonization of the implant with subsequent biofilm formation. In these cases, soft tissue biopsies often prove to be culture negative. Consequently, detachment of the causative adherent bacteria is crucial for correct microbiological diagnosis. Using an in vitro model, we compared 4 methods of biofilm sampling from metal surfaces.


METHODS
Discs of titanium and steel were incubated in the presence of Staphylococcus aureus, Staphylococcus epidermidis, Enterococcus faecalis, and Propionibacterium acnes in Mueller Hinton broth. Non-adherent bacteria were removed by repeated rinsing of the discs. 10 parallels of each disc were subjected to 1 of 4 methods for bacterial recovery: (A) sonication of the discs, (B) scraping of the discs using surgical blades followed by streaking of the blades onto agar plates, (C) scraping of the discs followed by vortex mixing of the surgical blades, and (D) scraping of the discs followed by sonication of the surgical blades. Quantitative bacterial cultures were performed for each sampling method.


RESULTS
With the exception of S. epidermidis on steel, sonication efficiently and reliably dislodged biofilm bacteria. The scraping methods employed did not detach bacteria embedded in biofilm.


CONCLUSIONS
Scraping of metal surfaces is not an adequate method for sampling of biofilm bacteria in vitro.
Bjerkan
Geir
G
Department of Orthopaedic Surgery, St Olav's University Hospital, Trondheim, Norway. geir.bjerkan@ntnu.no
Witsø
Eivind
E
Bergh
Kåre
K
D001422:Bacterial Adhesion; D001431:Bacteriological Techniques; D018441:Biofilms / Q000254:growth & development; D015169:Colony Count, Microbial; D013293:Enterococcus faecalis / Q000254:growth & development; D004866:Equipment Contamination; D006801:Humans; D050296:Microbial Viability; D011425:Propionibacterium acnes / Q000254:growth & development; D019736:Prostheses and Implants / Q000382:microbiology*; D016459:Prosthesis-Related Infections / Q000382:microbiology*; D013010:Sonication; D013193:Stainless Steel; D013211:Staphylococcus aureus / Q000254:growth & development; D013212:Staphylococcus epidermidis / Q000254:growth & development; D014025:Titanium
D013193:Stainless Steel; D014025:Titanium