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Key Points

  1. Findings on physical examination often suggest the origin and likely causative organisms in patients with infections involving the skin and subcutaneous tissues.

  2. When planning operative intervention for lymphadenitis, it is important to preoperatively plan either incision and drainage for abscess formation or lymphadenectomy for suspected mycobacterial infection.

  3. A high index of suspicion of necrotizing fasciitis and early surgical intervention are keys to optimizing patient outcomes.

  4. Laboratory and imaging studies are important adjuncts for the diagnosis of body cavity infections.

We live in a hostile environment. Since the beginning of life on earth, all living organisms have been under attack by would-be invaders seeking to use the nutrients within living tissues for their own survival, often to the detriment of the host. To combat the constant threat of invasion, all living organisms have developed measures to resist microbial invasion. In higher organisms, the mechanisms to resist microbial invasion have become quite complex and are usually extremely effective. However, occasionally resistance to invasion is overcome, due either to a break in host defenses or to a microbial adaptation that creates a more effective invader. When host invasion occurs, the resulting infection will frequently require medical treatment. In some cases, effective treatment also includes surgical intervention.

Unfortunately, many of the disease conditions that require surgical treatment, as well as the nature of the surgical intervention itself, alter host defense mechanisms and thus create further opportunities for microbial invasion. It is not surprising therefore that postoperative infection is the most common complication associated with many surgical procedures. Thus, instituting measures to decrease the risk of postoperative wound infections, in addition to early recognition and expeditious treatment of surgical site infections (SSIs) when they do occur, are essential aspects of optimal surgical care.

Host Defenses

Epithelial Barriers

In higher organisms, all exposed body surfaces (external and internal) are covered by a layer of epithelial cells that serve as a mechanical barrier against microbial invasion, while invasion between cells is inhibited by close apposition of the cellular membranes of adjacent epithelial cells. Besides creating a mechanical impediment to microbial invasion, most epithelial surfaces also have specialized adaptations that limit bacterial attachment and invasion. For example, the epidermis of the skin is composed of multiple layers of cells, the outer layers of which are inanimate, keratinized cells creating a dry, acidic inhospitable environment. Continuous cell shedding facilitates removal of attached organisms, while glandular secretions contain free fatty acids, lysozymes, and β-defensins that inhibit microbial growth. In the respiratory tract, a continuous layer of mucous covers the epithelial surface, trapping inhaled pathogens, which are then swept toward the pharynx by the continuous movement of cilia on the luminal surface of the epithelial cells. In addition, glandular secretions contain defensins and immunoglobulins that inhibit bacterial growth and attachment to epithelial surfaces. The urinary tract maintains sterility via a continuous flow ...

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