Bacterial skin disease in cats seldom occurs unless there is some underlying disorder promoting it. Trauma, malnutrition, parasitism, hormonal abnormalities, and immune system malfunctions can all predispose to the proliferation of bacteria on the skin.
Healthy skin has several mechanisms by which it resists infectious organisms. A dry, outer layer of keratin, combined with periodic shedding of dead skin cells, helps discourage population of the skin surface with harmful bacteria.
Even sebum, produced by the sebaceous glands of the skin, is antibacterial at normal concentrations. Finally, a normal population of bacteria that resides on the skin surface and in the hair follicles competitively inhibits the growth of disease-causing bacteria.
Problems can start to occur when the integument becomes traumatized, or underlying disease alters the normal integrity of the skin. If the skin’s defenses are penetrated in such a way, disease-causing bacteria found naturally in the environment can set up housekeeping.
Superficial bacterial skin disease can take on a number of appearances. These infections are limited to the outermost layers of the skin; however, if left untreated, they can spread to the inner layers, making treatment difficult and lengthy.