Bacterial exposure required to induce rabbit calvarial bone graft infection by superficial contamination.
Little is known about the minimum bacterial dose required to induce infections by superficial contamination alone (i.e., not direct inoculation). This study quantified superficial rabbit calvarial bone graft contamination by exposing parietal bone grafts to Staphylococcus aureus. Two 5 x 5-mm full-thickness calvarial bone grafts were harvested from 40 rabbits and contaminated with different concentrations (range = 10(7)-10(11) colony-forming units [CFUs]/mL) of S. aureus by immersion. One graft from each rabbit was cultured immediately, and the other was inset into a calvarial donor site, fixed in place with wire, and observed for evidence of infection. At harvest (28 days postoperatively), a bacterial exposure of greater than 10(8) CFUs/mL of S. aureus was required to induce infections in the rabbit calvarial grafts (p < 0.001, Student's t-test), transmitting an infectious dose of approximately more than 10(4) CFUs per graft. These results validate the previously known dogma regarding the number of organisms needed to manifest infection [1,2] and highlight a multifold increment in bacterial count needed to transmit this infectious dose by superficial contamination alone. Such a model may be useful in investigating the efficacy of various treatment modalities of contaminated bone.
Division of Plastic, Reconstructive and Oral-Maxillofacial Surgery, University of Pittsburgh Medical Center, Pennsylvania.
J F
JF
Lalikos
M P
MP
Mooney
J
J
Janosky
A
A
Losken
H W
HW
Losken
D000391:Air Microbiology; D000704:Analysis of Variance; D000818:Animals; D016025:Bone Transplantation / Q000009:adverse effects*; D016009:Chi-Square Distribution; D015169:Colony Count, Microbial; D004195:Disease Models, Animal; D008297:Male; D010019:Osteomyelitis / Q000209:etiology / Q000382:microbiology*; D010294:Parietal Bone / Q000637:transplantation; D011817:Rabbits; D013203:Staphylococcal Infections / Q000382:microbiology*; D013211:Staphylococcus aureus; D013530:Surgical Wound Infection / Q000209:etiology / Q000382:microbiology*