TY - JOUR

T1 - In vivo gentamicin susceptibility test for prevention of bacterial biofilms in bone tissue and on implants

AU - Jensen, Louise Kruse

AU - Bjarnsholt, Thomas

AU - Kragh, Kasper N.

AU - Aalbæk, Bent

AU - Henriksen, Nicole Lind

AU - Blirup, Sophie Amalie

AU - Pankoke, Karen

AU - Petersen, Andreas

AU - Jensen, Henrik Elvang

PY - 2019

Y1 - 2019

N2 - The objective of this study was to set up an in vivo gentamicin susceptibility test for biofilm prevention in bone tissue and on implants. Twenty-five pigs were allocated to six groups. Pigs in group A (n 6) were inoculated with saline. Pigs in groups B (n 6), C (n 3), D (n 3), E (n 3), and F (n 4) were inoculated with 10 l saline containing 10 4 CFU of Staphylococcus aureus. Different concentrations based on the MIC of gentamicin for the specific strain were added to the 10-l inoculum for groups C (160 MIC), D (1,600 MIC), E (16,000 MIC), and F (160,000 MIC). The inocula were injected into a predrilled tibial implant cavity, followed by insertion of a steel implant (2 by 15 mm). The pigs were euthanized after 5 days. In vitro, all the doses used were found to be bactericidal after up to 6 h. All implant cavities of pigs inoculated with bacteria and bacteria plus 160 MIC or 1,600 MIC of gentamicin were positive for S. aureus. In animals in each of groups E (16,000 MIC) and F (160,000 MIC), 2/3 and 1/4 of the implant cavities were S. aureus positive, respectively. By grouping groups C and D (10,000 MIC) and groups E and F (10,000 MIC), a significant decrease in the number of implant-attached bacteria was seen only between the high-MIC-value group and group B. Histologi-cally, it was demonstrated that 1,600, 16,000, and 160,000 MIC resulted in a peri-implant tissue reaction comparable to that in saline-inoculated animals. In vivo, the antimicrobial tolerance of the inoculated planktonic bacteria was increased by in vivo-specific factors of acute inflammation. This resulted in bacterial aggregation and biofilm formation, which further increased the gentamicin tolerance. Thus, susceptibility patterns in vitro might not reflect the actual in vivo susceptibility locally within a developing infectious area.

AB - The objective of this study was to set up an in vivo gentamicin susceptibility test for biofilm prevention in bone tissue and on implants. Twenty-five pigs were allocated to six groups. Pigs in group A (n 6) were inoculated with saline. Pigs in groups B (n 6), C (n 3), D (n 3), E (n 3), and F (n 4) were inoculated with 10 l saline containing 10 4 CFU of Staphylococcus aureus. Different concentrations based on the MIC of gentamicin for the specific strain were added to the 10-l inoculum for groups C (160 MIC), D (1,600 MIC), E (16,000 MIC), and F (160,000 MIC). The inocula were injected into a predrilled tibial implant cavity, followed by insertion of a steel implant (2 by 15 mm). The pigs were euthanized after 5 days. In vitro, all the doses used were found to be bactericidal after up to 6 h. All implant cavities of pigs inoculated with bacteria and bacteria plus 160 MIC or 1,600 MIC of gentamicin were positive for S. aureus. In animals in each of groups E (16,000 MIC) and F (160,000 MIC), 2/3 and 1/4 of the implant cavities were S. aureus positive, respectively. By grouping groups C and D (10,000 MIC) and groups E and F (10,000 MIC), a significant decrease in the number of implant-attached bacteria was seen only between the high-MIC-value group and group B. Histologi-cally, it was demonstrated that 1,600, 16,000, and 160,000 MIC resulted in a peri-implant tissue reaction comparable to that in saline-inoculated animals. In vivo, the antimicrobial tolerance of the inoculated planktonic bacteria was increased by in vivo-specific factors of acute inflammation. This resulted in bacterial aggregation and biofilm formation, which further increased the gentamicin tolerance. Thus, susceptibility patterns in vitro might not reflect the actual in vivo susceptibility locally within a developing infectious area.

KW - Aminoglycosides

KW - Animal models

KW - Biofilms

KW - Susceptibility testing

U2 - 10.1128/AAC.01889-18

DO - 10.1128/AAC.01889-18

M3 - Journal article

C2 - 30455228

AN - SCOPUS:85060777092

VL - 63

JO - Antimicrobial Agents and Chemotherapy

JF - Antimicrobial Agents and Chemotherapy

SN - 0066-4804

IS - 2

M1 - e01889-18

ER -