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Antibiotic usage in dermatology
Our ability to diagnose and treat diseases of all organ systems has progressed beyond even our most optimistic predictions of 50 years ago, and our understanding of human pathophysiology continues to make enormous advances. Unfortunately, however, our ability to treat bacterial pathogens with antibiotics has suffered enormous setbacks since the introduction of these drugs. In 1950, the antibiotic arsenal included penicillin, streptomycin and sulfonamides, followed by tetracyclines, chloramphenicol and erythromycin. Today, bacterial resistance has compromised the effectiveness of these antimicrobials. Until the last decade the development of new antibiotics has roughly kept pace with the continuing evolution of bacterial resistance to antimicrobials. Today, the problem of resistance has become far more serious, escalating to crisis proportions.
Antibiotic misuse is a major contributor to bacterial resistance. It has also been conclusively demonstrated that a decrease in the use of an antibiotic in a community may result in a decrease in the percentage of resistant pathogens in that community.
Dermatologists rely heavily on antibiotics to treat their patents for a variety of conditions; thus, it seems clear that policies and programs to foster the judicious use of antibiotics must be endorsed. These are common conditions for which dermatologists prescribe antibiotics, and where actions toward optimizing the use of these agents can be suggested.
Antibiotics are often prescribed for prophylaxis after cutaneous trauma or surgical wounds. Studies to prove antibiotics helpful in these clinical situations are difficult to conduct. There are, however, some prudent guidelines. When feasible, topical antimicrobials are preferred over systemic agents. This should be a general principle of dermatological antibiotic use, because topical application exposes only the sparse cutaneous bacterial flora to the agent, whereas systemic use causes all of the floral sites, including gastrointestinal, respiratory and genital, to undergo selection pressure for the development of resistance. Also, antibiotics, whether topical or systemic, should only be used as prophylaxis for wounds that have a significant likelihood of infection. Examples would include traumatic wounds in the tropics, where there is a high incidence of secondary infection, or surgical wounds in a “dirty” site. Antibiotic treatment should be directed toward the most likely pathogens rather than all potential organisms. Topical mupirocin, for example, with its narrow gram-positive spectrum, is a preferred agent for cuts or scratches incurred in the summer heat; prophylaxis for surgical wounds is best aimed at preventing staphylococcal and streptococcal infections, rather than a broader spectrum of organisms.
Impetigo is a superficial cutaneous infection by Staphylococcus aureus or Streptococcus pyogenes. Although usually a self-limited infection, most dermatologists treat minimal impetigo with a topical antibiotic. Extensive cases are treated with several days of a systemic antibiotic directed at Gram-positive cocci. Erysipelas and cellulitis are usually acute, potentially dangerous S. pyogenes infections of the dermis and subcutaneous tissue. Systemic therapy with a beta-lactam antibiotic is the optimal treatment. Bacterial folliculitis is most often a S. aureus infection of hair follicles which, when persistent, deserves topical or systemic anti-staphylococcal therapy, depending on the extent of infection. Furuncles and abscesses, and cutaneous purulent collections are best treated by drainage alone, where appropriate. Antibiotic treatment, although frequently given, is only indicated if there is significant associated cellulitis.
Patients with acute flares of atopic dermatitis or other types of eczema often respond more promptly to therapy if antibiotic treatment aimed at staphylococci and streptococci is part of the regimen. The rationale is that the gram-positive pathogens are often present in large numbers in dermatitic skin. Heavy colonization contributes to inflammation by causing toxin-mediated or superantigen-mediated release of cytokines and other inflammatory mediators. Decreasing the bacterial colonization results in decreased inflammation. Empiric antibiotic treatment might be recommended for all patients with severe inflammatory dermatoses. Topical antibiotics may be employed if the process is limited; systemic treatment is necessary to treat extensive inflammatory dermatoses.
Treating acne and rosacea
Acne vulgaris is an extremely common clinical condition in adolescents and young adults, for which dermatologists rely heavily on antibiotics. The pathology of acne involves the pilosebaceous follicle in the skin. Abnormal follicular keratinization and increased sebum production results both in comedone formation and overgrowth of Proprionibacterium acnes, which results in inflammation. Antibiotic therapy has a direct anti-inflammatory action, as well as reducing P. acnes counts in the follicles. Therapy with these drugs is typically recommended for patients with inflammatory acne, often intermittently or continuously, throughout the disease’s usual natural history of 8-12 years. In cases of mild inflammatory acne, topical antibiotics are used initially. Erythromycin and clindamycin are the common agents prescribed. More severe cases require treatment with oral antibiotics, often continued for years. The tetracyclines (i.e., tetracycline, doxycycline, minocycline), erythromycin and, to a lesser extent, clindamycin and sulfa-trimethoprim, are the oral antibiotics more typically used.
Chronic use of topical agents can lead to the development of resistant P. acnes and staphylococci. Multi-resistance in these organisms has also been demonstrated, although studies show that the development of resistance to topically-applied erythromycin is decreased by the concomitant application of benzoyl peroxide.
Resistance has been shown to emerge in the skin flora of household contacts of patients treated with topical antibiotics. Systemic use of antibiotics markedly amplifies resistance because of the increased number of bacteria exposed to selection pressures.
Alternative treatment regimens that do not rely on the use of antibiotics
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