Systemic Antimicrobial Therapies for Pressure Ulcers
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I n chronic wounds, an altered balance among the number of organisms present, their virulence, and host resistance leads to bacterial infection. Infected chronic wounds may manifest with a friable bright red granulating wound bed, localized pain, increased wound size, perilesional warmth and tenderness, erythema on the surrounding skin, malodorous base, and increased wound exudate. The final outcome of infected wounds depends on a balance between factors that promote further complications or lead to their resolution. Wound infection in the geriatric population merits especially assiduous control and rapid intervention because it adversely affects patients' psychological, functional, and medical status. Patients may fear that infection will progress, causing severe psychological distress due to pain or altered appearance; they may experience a rapid decline of their already compromised functional status.
Simple bacterial wound infections often are treated according to their morphological appearance and to clinical experience because only a few pathogens are involved (see Figure 1). Treatment of critical lesions such as infected pressure ulcers or foot ulcers in a person with diabetes once involved administering oral or parenteral antibiotics among normal hosts. Usually, patients with deeper infections are sicker and require more vigorous intervention. Intravenous antibiotics are often prescribed after hospital admission in these cases; surgical drainage and rapid debridement are necessary when the infectious process is deep, extending down to fascia or muscle (see Figure 2). In recent decades, with a dramatic development of several groups of antimicrobial agents, the clinician has been faced with a long list of new antibiotics1 that may be lacking meaningful comparative information. Because of the large number of new agents in clinical practice, terms such as "new generation" antibiotics are commonly used.
Pressure ulcers are commonly colonized by several organisms in the absence of clinical signs of infection (see Table 1). When infection is present, the significance of laboratory tests must be critically evaluated and drug susceptibility tests must be considered according to the clinician's experience and the evidence base from the literature.2 On the other hand, some organisms that once had predictable antibiotic susceptibility characteristics now have become resistant.3 The rapid emergence of antibiotic-resistant bacteria has been highlighted by Colsky et al4 in an ongoing surveillance of patients with complicated skin infections that required hospitalization. In this study, 50% of Staphylococcus aureus isolates from chronic wounds was resistant to oxacillin, with 36% of Pseudomonas isolates resistant to ciprofloxacin. A comparison between these data and previous data obtained by the same authors for the same group of patients5 demonstrated an increasing trend in antibiotic resistance for different species of bacteria involved in soft and deep skin infections.
A favorable clinical outcome is achieved in infected pressure ulcers when the patient is in stable condition and systemic treatment is established together with good local care (ie, a combination of surgical debridement and exudate control). The antimicrobial drug regimen must be adjusted according to the clinical response of the patient. If marked discrepancies are evident between drug susceptibility tests and clinical response, the following possibilities must be considered: inappropriate selection of drug dosage or route of administration, the emergence of drug-resistant bacteria, and the additional participation of micro-organisms not previously detected.
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