Pyoderma refers to any purulent disease of the skin, but this communication is restricted to only certain bacterial infections of the skin. Such infections can be either primary or secondary. Although "pyo-" indicates the presence of pus, certain instances of infection may not be pus-producing, for example, staphylococcal bullous impetigo.1 Nonbacterial, pus-producing skin disease's, such as pustular psoriasis, are not discussed.
Impetigo and furunculosis are the most significant bacterial infections of the skin. Chronic, deeper infections, termed ecthyma, probably start as impetigo. Both bacterial folliculitis and carbuncles are anatomical variants of furunculosis. Diffuse interstitial infection is termed cellulitis, and erysipelas is a superficial variant. Almost any dermatosis in which the stratum corneum is broken can become secondarily infected. colonization by pathogens ( coagulase-positive staphylococci and β hemolytic streptococci) is common, but manifest disease is relatively uncommon. There are skin diseases in which bacteria can be recovered from the lesions, but
Fritsch WC. Therapy of Impetigo and Furunculosis. JAMA. 1970;214(10):1862-1866. doi:10.1001/jama.1970.03180100056010