Isolation of Staphylococcus hyicus subsp. hyicus from pigs affected with exudative epidermitis and experimental infection of piglets with isolates.

Five strains of Staphylococcus hyicus subsp. hyicus were isolated: three strains (P-1, P-2 and P-3) from the crust on the body surface of 6-month-old pigs on a farm in Aomori prefecture, and two (P-5 and P-6) from both the crust on the body surface and the joint of a 1-month-old piglet with exudative epidermitis (EE) on another farm. The characterization of the isolates and the experimental infection of the piglets with strain P-1 were carried out. Subcutaneous inoculation with the bacterial suspension (10(10) CFU) produced EE to all nine piglets. Eight of them had exudation and exfoliation within 24 hr of infection. Histopathologically, disappearance of stratum corneum and necrosis with vacuolar degeneration of prickle cells were remarkable in the epidermis. Infiltration of neutrophils and lymphocytes were observed in the dermis. The results clearly indicate that S. hyicus is responsible for incrustation of the body surface of weanling pigs and exudative epidermitis in young piglets.