(BQ) Part 2 book "Cases in medical microbiology and infectious diseases" presentation of content: Skin and soft tissue infections, central nervous system infection, systemic infections, advanced cases. | SECTION FOUR SKIN AND SOFT TISSUE INFECTIONS 255 7/24/14 11:44 AM 256 Skin and Soft Tissue Infections I N T ROD UC T I O N T O S E C T I ON IV The resistance of skin to infection is due to the integrity of the keratinized skin, the presence of inhibitory fatty acids produced by sebaceous glands, the dryness of the skin, and the inhibitory effect of the resident normal skin microbiota. Skin and soft tissue infections can be caused by either direct penetration of a pathogen through the skin or hematogenous spread of the pathogen to the site. The normal skin microbiota includes organisms that may cause infection in the setting of a disruption in the integrity of the skin (such as the presence of a surgical suture or an insect bite). In the setting of severe damage to the skin, as occurs with burns, even normally innocuous organisms, including endogenous bacteria, can cause severe disease. Similarly, when the skin is no longer dry, as may occur in moist intertriginous spaces or when occlusive dressings are present, the patient is at increased risk of infection. Cutaneous manifestations of systemic disease are common. Rocky Mountain spotted fever, meningococcemia, enteroviral infection, and toxic shock syndrome can all present with fever and a diffuse erythematous macular rash. Other systemic infections that can present with a diffuse rash include scarlet fever, measles, and German measles. The characteristic rash of Lyme disease, erythema migrans, is specific enough to establish the diagnosis. The nature of the lesion (macular, papular, vesicular, pustular, or bullous) may help to narrow the differential diagnosis. For example, varicella-zoster virus infection typically results in vesicular skin lesions. The rash of secondary syphilis, on the other hand, may present clinically as macular, papular, maculopapular, or pustular skin lesions but does not present as a vesicular rash. Skin and soft tissue infections can be classified on the .
