Bacterial biofilm formation after nasal packing in nasal mucosa-wounded mice

Bacterial biofilm plays an important role in recalcitrant chronic rhinosinusitis. Staphylococcus aureus is a crucial pathogen in chronic rhinosinusitis and S. aureus biofilm is related to unfavorable postoperative outcomes. Although S. aureus is known to be the most common bacteria leading to postoperative infection, whether biofilm forms on the wound surface after functional endoscopic sinus surgery and the relationship between biofilm formation and surgery are still not clear. This study was designed to observe whether S. aureus biofilm forms in mice with wounded nasal mucosa mice after bacteria inoculation.

Three hundred twenty-four wild-type male C57BL/6 mice were recruited for the experiment. Except for the four used in the preliminary experiment, the mice were randomly divided into four groups: a wound plus packing group (group A), a wound group (group B), a packing group (group C), and a control group (group D). After treatment, groups A, B, and C were inoculated with S. aureus suspension at 1 × 10(9) CFU/mL in the right nasal cavity; sterile physiological saline was used instead of bacteria suspension for group D. Confocal laser scanning microscopy was used to detect the biofilm. A nasal lavage culture was also completed.

Biofilm formation was found in group A on the 3rd, 7th, and 15th days after inoculation with growth rates of 10, 25, and 40%, respectively. Three cases of biofilm were also detected in group B on the 15th day postinoculation. There was no biofilm observed on the nasal mucosa in group C or D. The nasal lavage culture showed that the inoculated bacteria stayed on the nasal mucosa temporarily after inoculation.

Our results indicate that a nasal wound, nasal packing, and the existence of pathogenic bacteria are all essential elements for biofilm formation in healthy mice. This result indicated that biofilm formation may be avoided by shortening the duration of nasal packing and reducing the nasal wound.