Early Biofilm Formation on the Drain Tip after Total Knee Arthroplasty Is Not Associated with Prosthetic Joint Infection: A Pilot Prospective Case Series Study of a Single Center

Abstract

Background: Periprosthetic joint infection (PJI) is a devastating complication of arthroplasties that could occur during the surgery. The purpose of this study was to analyze the biofilm formation through microbiological culture tests and scanning electron microscopy (SEM) on the tip of surgical drainage removed 24 h after arthroplasty surgery.

Methods: A total of 50 consecutive patients were included in the present prospective observational study. Drains were removed under total aseptic conditions twenty-four hours after surgery. The drain tip was cut in three equal parts of approximately 2-3 cm in length and sent for culture, culture after sonication, and SEM analysis. The degree of biofilm formation was determined using a SEM semi-quantitative scale.

Results: From the microbiological analysis, the cultures of four samples were positive. The semi-quantitative SEM analysis showed that no patient had grade 4 of biofilm formation. A total of 8 patients (16%) had grade 3, and 14 patients (28%) had grade 2. Grade 1, scattered cocci with immature biofilm, was contemplated in 16 patients (32%). Finally, 12 patients (24%) had grade 0 with a total absence of bacteria. During the follow-up (up to 36 months), no patient showed short- or long-term infectious complications.

Conclusions: Most of the patients who underwent primary total knee arthroplasty (TKA) showed biofilm formation on the tip of surgical drain 24 h after surgery even though none showed a mature biofilm formation (grade 4). Furthermore, 8% of patients were characterized by a positivity of culture analysis. However, none of the patients included in the study showed signs of PJI up to 3 years of follow-up.

Keywords: biofilm; infection disease; periprosthetic joint infection; surgical drainage; total knee arthroplasty.

Figure 1

(A) The removal of the surgical drain on the first day after TKA surgery performed in a sterile and standardized manner. (B) Surgical drain tip section on a sterile surface.

Figure 2

Low magnification of SEM image showing the tip of the drain sectioned longitudinally.

Figure 3

Grade 0. Absence of pathogenic cells. (A) Scattered red blood cells (*) are visible in the background. No pathological cells are detectable. (B) Blood clot.

Figure 4

Scattered cocci, immature biofilm (covering < 25% of the specimen surface). (A) Bacterial cells appear irregular, without a matrix covering (orange arrow). (B–D) Cells were arranged either as individual cells, or as short chains with a filamentous projection of extracellular matrix (orange arrows). Red blood cells (*).

Figure 5

Partially mature biofilm (covering < 50% of the specimen surface). (A) Bacterial cells are arranged in a cluster, with extracellular matrix in the background. (B) High magnification. Bacterial cells are arranged in a cluster (orange arrow). Red blood cells (*).

Figure 6

Mature biofilm (covering between 50 and 75% of the specimen surface). (A–D) Images of biofilm structure. Biofilms show a cobwebbed appearance, with an amorphous polymeric extracellular matrix surrounding (orange arrow) and interconnecting bacteria. Red blood cells (*).