Summary
ST autografts for ACLR were commonly contaminated with skin commensal bacteria during harvest.
Abstract
Purpose
Hamstring autografts in anterior cruciate ligament reconstruction (ACLR) were found to be more susceptible to postoperative deep knee infection compared to other auto- and allografts. The parameters that explain the vulnerability of hamstring grafts to infection have not been well studied yet. Bacterial contamination during retrieval and the preparation of the graft are the most accepted hypothesis
The purpose of this study was to investigate the rate of bacterial contamination of semitendinosus (ST) tendons during graft harvest in (ACLR), in order to precisely specify the underlying pathogens and obtain data on their susceptibility to potential antibiotics.
Methods
In a prospective study, a total of 59 consecutive patients undergoing primary ACLR were recruited from one center. No patient had history of previous surgery to the knee or showed clinical signs of infection. Four tissue samples of harvested ST tendons for anterior cruciate ligament (ACL) autografts (case group; ST) were examined for evidence of bacterial colonization and compared to four tissue samples of the native ACL as negative controls (control group; ACL). Three of the respective samples were subjected to cultural microbiological examination and one to 16S rRNA-PCR. Antibiotic susceptibility testing was performed for each pathogen that was identified.
Results
A total of 342 samples were analyzed by culture. Significantly more patients showed a positive culture of the ST (33.9%; n=20/59) compared to 3.4% of patients (n=2/59) with positive culturing of the ACL (p< 0.0001). Including 16S rRNA-PCR, in a total of 42.4% (25/59) of patients, bacteria were detected in at least one ST sample either by PCR and/or culture. All species found (n=33) belong to the typical skin flora with Staphylococcus epidermidis (39.4%; n=13/33) being the most common species, followed by Staphylococcus capitis (24.2%; n=8/33). All tested isolates (n=29) were susceptible to vancomycin (29/29, 100%), 69% (n=20/29) to oxacillin and 65.5% (n=19/29) to clindamycin.
Conclusion
ST autografts for ACLR were commonly contaminated with skin commensal bacteria during harvest. One third of the isolates showed resistance to typical perioperative intravenous antibiotics, whereas all isolates were sensitive to vancomycin. Therefore, routine prophylactic decontamination of all hamstring autografts before implantation should be recommended, preferably with topical vancomycin.