Furuncle-like lesions in mouse experimental skin infections with Staphylococcus aureus

Abstract

The pathomechanism of furuncle has not been fully elucidated and should be investigated using an appropriate animal model. We observed the invasion of Staphylococcus aureus cells into hair follicles in mice, using a strain of S. aureus isolated from human furunculosis. Light microscopical examination revealed that S. aureus cells attached to corneocytes at 6 h after inoculation, proliferated around the ostium of the hair follicle and invaded the hair follicle at 12 h after inoculation. Electron microscopically, S. aureus cells attached to the horny layer of hair follicle with long, thick, string-like structures. At 12 h after inoculation, S. aureus cells invaded in a file between the inner root sheath and outer root sheath. We could not induce direct invasion from the follicle ostium. Our findings suggest that there are some regions of the hair follicle through which S. aureus cells can relatively easily invade deeper into the follicle. The most important question is what confines the invasion and inflammation of S. aureus to the hair follicle. We suggest that there is some locus minoris for invasion into hair follicles by S. aureus, such as an interface between the two sheaths.