Quantification of Staphylococcus aureus adhesion to equine bone surfaces passivated with Plasmalyte and hyperimmune plasma.
OBJECTIVE
To quantify the adhesion of Staphylococcus aureus to 4 equine bone surfaces passivated in a balanced polyionic solution (Plasmalyte) or hyperimmune equine plasma (Polymune plasma).


METHODS
In vitro comparative study.


METHODS
Third metacarpal bone (MC3) surface explants from 9 equine cadavers.


METHODS
Approximately 1 cm(2) sections of periosteum were removed from MC3 and stapled to sterile stainless steel screens. Three bone surface explants were cut using a surgical saw to present 1 cm(2) surfaces of subperiosteal bone, cut cortical bone, or endosteum. Duplicate explants of each surface were immersed for 1 hour in Plasmalyte or hyperimmune equine plasma. Each explant was then placed in a well of a 6-well sterile tissue culture plate with the surface of interest exposed. Each surface was inoculated with approximately 100 colony-forming units of S. aureus in 10 microL of Mueller Hinton broth and incubated for 6 hours at 37 degrees C. After gentle rinsing to remove non-adherent bacteria, samples were sonicated for 5 minutes at 60 kHz to loosen adhered bacteria. The number of adherent bacteria was determined by serial dilutions and incubation of the sonicate. Scanning electron microscopy (SEM) was performed on samples identically treated from an additional horse to confirm bacterial removal by sonication from all surfaces and support quantitative culture results.


RESULTS
Less S. aureus adhered to periosteum than to cortical bone, cut cortical bone, and endosteal surfaces, which were all similar. Exposure of all surfaces to hyperimmune plasma reduced S. aureus adherence compared with Plasmalyte exposure; SEM supported these conclusions.


CONCLUSIONS
Less bacteria adhere to periosteum than other bone surfaces. Hyperimmune plasma reduces bacterial adhesion to all bone tissue surfaces.


CONCLUSIONS
Understanding the factors that affect bacterial adhesion to bone will facilitate development of improved intraoperative lavage solutions to reduce the morbidity and mortality associated with postoperative infection.
Bauer
Sandra M
SM
School of Veterinary Medicine, the Department of Statistics, and the College of Medicine, University of Wisconsin, Madison, WI 53706, USA.
Santschi
Elizabeth M
EM
Fialkowski
James
J
Clayton
Murray K
MK
Proctor
Richard A
RA
D000818:Animals; D001422:Bacterial Adhesion / Q000502:physiology; D005260:Female; D050723:Fractures, Bone / Q000150:complications / Q000382:microbiology / Q000601:surgery / Q000662:veterinary*; D006734:Horse Diseases / Q000382:microbiology*; D006736:Horses / Q000293:injuries / Q000601:surgery; D008297:Male; D008663:Metacarpus / Q000293:injuries / Q000382:microbiology* / Q000601:surgery; D010949:Plasma; D013211:Staphylococcus aureus / Q000502:physiology* / Q000648:ultrastructure; D007507:Therapeutic Irrigation / Q000379:methods / Q000662:veterinary*; D014946:Wound Infection / Q000517:prevention & control / Q000662:veterinary