Chronic surgical site infection due to suture-associated polymicrobial biofilm

Abstract

Background: Surgical site infection (SSI) is a common surgical complication; culture-negative SSI presents a particular problem in management.

Methods: Examination of explanted foreign bodies (sutures) using confocal laser scanning microscopy (CLSM) and fluorescent in situ hybridization (FISH) after surgical exploration of a chronic culture-negative SSI.

Results: Confocal microscopy (CM) demonstrated bacilli and cocci attached to the surface of the explanted sutures in a mixed biofilm. Fluorescent in situ hybridization confirmed that Staphylococci were components of the mixed biofilm. Removal of the foreign bodies (sutures) resolved the chronic infection.

Conclusion: Chronic SSI can arise from underlying bacterial biofilms, which can invest implanted foreign bodies and associated soft tissue surfaces.

FIG. 1.

Intraoperative views of the draining sinuses. (A) Green suture material was visible in the depth of the sinuses after curetting of the sinus tracks; the surrounding limited erythema is consistent with a localized infectious focus. (B) Suture material resident in the abdominal wall after removal of overlying skin and fat. (Color image is available online at www.liebertpub.com/sur)

FIG. 2.

Confocal microscopic examination of explanted suture material. (A) Viability staining showing a biofilm (arrow) attached to the suture braids (autofluorescing red). Green and yellow bacteria indicate viable cells at the wound site. (B) Higher magnification of the crevice region between the braids of the suture showed that the biofilm was polymicrobial, consisting of bacilli and cocci. (Color image is available online at www.liebertpub.com/sur)

FIG. 3.

Fluorescent in situ hybridization shows Staphylococcal cells (yellow) in a patchy biofilm attached to the reactive soft tissue that enveloped the infected suture. The nuclei of the host cells were stained red with propidium iodide, and f-actin in the cytoplasm was stained blue with phalloidin. (A) Isometric view showing small biofilm cell clusters and single cells attached to the tissue. (B) Plan view of the biofilm in a different area of tissue. The XZ and YZ sagittal sections through the host tissue and biofilm are shown below and to the right of the plan view, respectively. (Color image is available online at www.liebertpub.com/sur)