Summary

espite attempted maintenance of a sterile surgical field, some bacterial contamination was detected in 50% of cases.

Abstract

Introduction

The rate of post-operative septic arthritis following ACL reconstruction is low overall with reports of around 1%. Recent literature has described the phenomenon of subclinical bacterial colonization of soft tissue grafts and the development of biofilms. This colonization has been implicated as a potential contributor to graft failure, as prior studies have isolated bacterial DNA in failed ACL graft samples taken at the time of revision surgery, and in the right host environment, could progress to symptomatic intra-articular infection. This study assessed the presence of bacterial contamination on surgical gloves at various timepoints throughout an ACL reconstruction. We hypothesized that despite standard procedure to maintain sterility bacterial contamination would be present.

Methods

Bacterial contamination of gloves was assessed in 16 ACL reconstructions (8 bone-patellar tendon-bone autograft; 8 hamstring autograft). Timepoints of sample collection were: 1) After patient draping, 2) After graft harvest, 3) After graft preparation, and 4) Prior to graft passage. Graft tissue samples were also cultured. At these timepoints, the primary surgeon pressed their gloved fingers onto a sterile Tryptic Soy Agar (TSA) plate. Outer gloves were then removed and replaced with fresh sterile gloves to proceed with surgery. TSA plates were incubated for 48 hours at 37°C and 5% CO2 and checked for bacterial growth. Colonies, if present, were transferred to TSB broth using a sterile loop and then incubated for 24hrs and spun down to form cell pellets, that were subsequently sequenced to evaluate for bacteria.

Results

8/16 cases (50%) a sample with bacterial growth. 9/96 (9%) agar plates collected were positive for bacterial growth at three different time points. 1/16 plates (6%) after graft harvest had one CFU. 1/16 platers (6%) collected after graft preparation had one CFU. 7/48 (15%) plates demonstrated growth prior to graft passage. 3/16 tissue samples (19%) were positive for bacterial growth. No negative control plates were found to have bacterial growth. Fischer exact testing found no statistically significant difference between time points.

Conclusion

Despite attempted maintenance of a sterile surgical field, some bacterial contamination was detected in 50% of cases. The low level of bacterial contamination detected during this study are of uncertain clinical significance. Longitudinal follow-up of positive cases could elicit clinical implications of detecting bacteria at the time of surgery, without overt post-operative septic arthritis, including monitoring for graft failure.