Effects of β-toxin of Staphylococcus aureus on ciliary activity of nasal epithelial cells

Abstract

Objectives: To investigate the in vitro effects of staphylococcal β-toxin on ciliary activity and the in vivo effects on sinusitis induction. Study Design: The in vitro effects of staphylococcal β-toxin on ciliary activity were investigated at different concentrations and exposure times. Experimental sinusitis was induced in rabbits with application of β-toxin and confirmed 7 days later. Methods: Ciliated epithelial cells were taken from the maxillary sinus mucosa of 10 rabbits. Five culture dishes from each rabbit were used for the experimental group, and one culture dish from each rabbit was used for the control group. In the experimental group, ciliary beat frequency (CBF) was measured at concentrations of 0.1, 1, 2, 5 and 10 U/mL of β-toxin using a video-computerized analysis technique, while in the control group, culture medium containing no toxin was used. CBF was measured 1, 2, 4, 6, 8, 12, 24, and 48 hours after administration of β-toxin. To induce experimental sinusitis, 2 U/mL of β-toxin was percutaneously applied to the maxillary sinus of 10 rabbits without occlusion of the natural ostium, while normal saline was percutaneously applied to the right-side maxillary sinus of 4 rabbits in the control group. At 7 days, mucosal membranes were taken from the inferomedial wall of the maxillary sinus for light microscopic study. Results: CBF dropped significantly after an 8-hour incubation at 2, 5, and 10 U/mL of β-toxin. No ciliary activity was observed after a 24-hour incubation at 2 and 5 U/mL and a 12-hour incubation at 10 U/mL of β-toxin. Mucoid, purulent discharge was observed in the maxillary sinuses of the β-toxin-applied group. Prominent epithelial disruption and infiltration of inflammatory cells into the epithelium and lamina propria were observed in the β-toxin-applied group. Conclusions: Staphylococcal β-toxin may reduce ciliary activity and induce sinusitis without occlusion of the natural ostium of the maxillary sinus in rabbits. This study provides another animal model of sinusitis for understanding the pathogenesis of sinusitis induced by bacterial exotoxins.