Antimicrobial therapy skin infections

Many areas of the human body are colonized with bacteria— this is known as normal flora. Infections often arise from one s own normal flora (also called an endogenous infection). Endogenous infection may occur when there are alterations in the normal flora (e.g., recent antimicrobial use may allow for overgrowth of other normal flora) or disruption of host defenses (e.g., a break or entry in the skin). Knowing what organisms reside where can help to guide empirical antimicrobial therapy (Fig. 66-1). In addition, it is beneficial to know what anatomic sites are normally sterile. These include the cerebrospinal fluid, blood, and urine. 

Every patient receiving antimicrobial therapy for skin and soft tissue infections must be monitored for efficacy and safety. Efficacy typically is manifested by reductions in temperature, white blood cell count, erythema, edema, and pain that begin within 48 to 72 hours. To ensure safety, dose antibiotics according to renal and hepatic function as appropriate, and monitor for and minimize adverse drug reactions, allergic reactions, and drug interactions. 

Systemic therapy with a variety of (3-lactams, macro-lides and lincosamides (clindamycin) has been the cornerstone of skin infection therapy for many years [17]. However, topical antibiotics can play an important role in both treatment and prevention of many primary cutaneous bacterial infections commonly seen in the dermatological practice [18], Indeed, while systemic antimicrobials are needed in the complicated infections of skin and skin structure, the milder forms can be successfully treated with topical therapy alone [18], The topical agents used most often in the treatment of superficial cutaneous bacterial infections are tetracyclines, mupirocin, bacitracin, polymyxin B, and neomycin. 

Occlusive therapy Occlusive dressings such as a plastic wrap increase skin penetration by 10-fold. Discontinue the use of occlusive dressings if infection develops and institute appropriate antimicrobial therapy. 

Oral therapy of infections is usually cheaper and avoids the risks associated with maintenance of intravenous access on the other hand, it may expose the gastrointestinal tract to higher local concentrations of antibiotic with consequently greater risks of antibiotic-associated diarrhoea. Some antimicrobial agents are available only for topical use to skin, anterior nares, eye or mouth in general it is better to avoid antibiotics that are also used for systemic therapy because topical use may be especially likely to select for resistant strains. Topical... 

There are certain infections which, due to the relative inaccessibility of the causative microorganisms to antimicrobial agents, invariably require a prolonged duration (3-5 weeks, rather than 5-8 days) of therapy. They include prostatitis, osteomyelitis and skin infections in dogs, and Khodococcus equi pneumonia in foals (6-16 weeks of age). In the treatment of these infections, preference should be given to the use of orally effective antimicrobial agents. 

Cutaneous Mo.st (about 95%) anthrax infections occur when the bacterium enters a cut or abrasion on the. skin, such as when handling contaminated wool, hides, leather or hair products (especially goat hair) of infected animals. Skin infection begins as a raised itchy bump that resembles an insect bite but within 1-2 days develops into a vesicle and then a painless ulcer, usually 1 -3 cm in diameter, with a characteristic black necrotic (dying) area in the center. Lymph glands in the adjacent area may swell. About 20% of untreated cases of cutaneous anthrax will result in death. Deaths are rare with appropriate antimicrobial therapy. 

The proper route of administration for an antimicrobial depends on the site of infection. Parenteral therapy is warranted when patients are being treated for febrile neutropenia or deep-seated infections such as meningitis, endocarditis, and osteomyelitis. Severe pneumonia often is treated initially with intravenous antibiotics and switched to oral therapy as clinical improvement is evident. Patients treated in the ambulatory setting for upper respiratory tract infections (e.g., pharyngitis, bronchitis, sinusitis, and otitis media), lower respiratory tract infections, skin and soft tissue infections, uncomplicated urinary tract infections, and selected sexually transmitted diseases may receive oral therapy. 

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