New quantitative image analysis of staphylococcal biofilms on the surfaces of nontranslucent metallic biomaterials.
BACKGROUND
Implant-related infection after orthopedic surgery is difficult to cure. One of the causes of infection is the bacterial biofilm that forms around biomaterials used during surgery. Therefore, it is necessary to investigate bacterial biofilms extensively to resolve the problems of these postoperative infections. However, no established culture method or quantification system exists for bacterial biofilms grown on the surface of the metallic biomaterials used in orthopedics, which are nonradiolucent. The purpose of this study was to develop a quantitative method to evaluate the difference in resistance of stainless steel versus titanium to staphylococcal biofilms and the efficacy of antibiotics against biofilms.


METHODS
The bacterial strains used in this study were three Staphylococcus aureus stains: strain Seattle 1945 and two clinical strains cultured from postoperative infections. Staphylococcal biofilms were formed on stainless steel washers (SUS304) and titanium washers (pure titanium). They were stained with crystal violet and were examined with a digital microscope to calculate the bacterial coverage rate (BCR) by NIH imaging.


RESULTS
The BCR of S. aureus biofilms formed on stainless steel and titanium washers increased over time. At 24, 48, and 72 h after cultivation, the amount of biofilm on the surface of the stainless steel washers was significantly greater or tended to be greater than that on the titanium. Cefazolin was applied to the obtained biofilms of two clinically isolated S. aureus strains. Cefazolin did not eradicate the biofilms but significantly reduced the biofilm of one strain.


CONCLUSIONS
The newly developed quantitative method (static microtube culture and measurement system) was useful for assessing the amount of bacterial biofilms on the surface of nontranslucent biomaterial. We found that titanium may be more resistant to bacterial infection than stainless steel. To control implant-related severe infections, the biomaterials should be assessed from the viewpoint of their resistibility to bacterial adhesions and infections.
Adachi
Kouichi
K
Department of Orthopaedic Surgery, Graduate School of Biomedical Science, Nagasaki University, 1-7-1 Sakamoto, Nagasaki 852-8501, Japan.
Tsurumoto
Toshiyuki
T
Yonekura
Akihiko
A
Nishimura
Seisuke
S
Kajiyama
Shiro
S
Hirakata
Yoichi
Y
Shindo
Hiroyuki
H
D000900:Anti-Bacterial Agents / Q000627:therapeutic use; D001672:Biocompatible Materials; D018441:Biofilms / Q000187:drug effects; D002437:Cefazolin / Q000627:therapeutic use; D006801:Humans; D007091:Image Processing, Computer-Assisted; D013193:Stainless Steel; D013211:Staphylococcus aureus / Q000187:drug effects / Q000502:physiology*; D013499:Surface Properties; D014025:Titanium
D000900:Anti-Bacterial Agents; D001672:Biocompatible Materials; D013193:Stainless Steel; D014025:Titanium; D002437:Cefazolin