THE MACROSCOPIC AND MICROSCOPIC EFFECTS OF INTRADERMAL INJECTION OF CRUDE AND PURIFIED STAPHYLOCOCCAL EXTRACTS ON CANINE SKIN

Intradermal injection of staphylococcal protein A, and crude extracts of Staphylococcus intermedius and Staphylococcus aur eus in normal dog s elicited dose-dependent increases in skin fold thickness. The most c oncentrated doses of S. intermedius elicited a significantly greater r esponse than the equivalent dose of S. aureus between 30 min and 4 h a fter injection (p < 0.05). This may be due to prior sensitisation or m ay indicate that S. intermedius is more virulent. At all other times a nd doses there was no significant difference between the two crude sta phylococcal extracts. Histological examination indicated that while th ere were differences between the responses to the three extracts, all three elicited similar epidermal lesions (sub-corneal pustules, spongi osis and hyperplasia) and superficial perivascular dermatitis. A simil ar pattern of changes has been recorded in canine superficial pyoderma supporting the hypothesis that penetration of staphylococcal products into the dermis is involved in the pathogenesis of the lesions of pyo derma.