| Healthcare-Associated Infections: CAP/VAP/MRSA |
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Healthcare-Associated Infections: CAP/VAP/MRSA Marin Kollef, MD Professor of Medicine, Washington University School of Medicine, St. Louis, Missouri In recent years, healthcare-associated pneumonia (HCAP) has increasingly been recognized as distinct from several related conditions, including community-acquired pneumonia (CAP), nursing home-acquired pneumonia, hospital-acquired pneumonia (HAP), and ventilator-acquired pneumonia (VAP). Important demographic characteristics that distinguish patients with HCAP from those with other forms of pneumonia include a greater number of medical comorbidities (eg, diabetes and cardiovascular disease), infections with certain microorganisms (including methicillin-resistant Staphylococcus aureus [MRSA] and gram-negative species), older age, recent hospitalization, and admission to the hospital from a nursing home.1,2 However, it should be recognized that every institution has a distinct patient population with its own risk factor profile for HCAP. Mortality is generally highest for patients with VAP, is intermediate with HCAP or HAP, and is lowest with CAP. These differences in mortality may be due, at least in part, to differences in underlying comorbidities.1 The most common infectious organisms among individuals with HCAP include MRSA and Pseudomonas aeruginosa. Risk factors for HCAP are common among patients presenting to a hospital emergency department (ED), but are often not recognized by treating physicians. The failure to identify high-risk patients may lead to the selection of inappropriate initial antimicrobial therapy. Some studies have found that patients in the ED who have MRSA or gram-negative species are at high risk of inappropriate antimicrobial treatment and substantial delays before appropriate therapy is initiated.3 The appropriate initial selection of antibiotics has been shown to significantly improve the survival of patients with resistant organisms, compared with patients who receive inappropriate initial antibiotic therapy.4 However, even when patients receive an appropriate antimicrobial agent, important determinants of clinical outcome remain unknown, including the susceptibility of the patient’s infection to the selected antimicrobial therapy, the concentration of antimicrobial agent in the target tissues, and the optimal dose of antimicrobial agent to treat infection without promoting resistance. Although the optimal dosing of antimicrobial therapy is not well defined, dosing clearly has an important effect on the efficacy of antimicrobial therapy in patients with HAP/VAP. Finally, although the initiation of appropriate therapy is important to improve survival, it is also important to avoid overuse of antibiotics in VAP and related conditions.5 Current management guidelines from the Infectious Diseases Society of America do not distinguish among HAP, VAP, or HCAP. Patients with all of these conditions are managed the same way: those with late-onset infection (≥5 days) or risk factors for multiresistant organisms receive broad-spectrum antibiotic therapy, and other patients receive limited-spectrum antibiotic therapy.6 Future guideline revision may recommend different management strategies for HCAP, HAP, or VAP, and will also reflect changing resistance patterns since the last guidelines in the selection of empiric antimicrobial therapy. References 1. Kollef MH, Shorr A, Tabak YP, et al. Epidemiology and outcomes of health-care-associated pneumonia: results from a large US database of culture-positive pneumonia. Chest. 2005;128:3854-3862. 2. Lescure FX, Locher G, Eveillard M, et al. Community-acquired infection with healthcare-associated methicillin-resistant Staphylococcus aureus: the role of home nursing care. Infect Control Hosp Epidemiol. 2006;27:1213-1218. 3. Kollef MH, Morrow LE, Niederman MS, et al. Clinical characteristics and treatment patterns among patients with ventilator-associated pneumonia. Chest. 2006;129:1210-1218. 4. Kollef KE, Schramm GE, Wills AR, et al. Predictors of 30-day mortality and hospital costs in patients with ventilator-associated pneumonia attributed to potentially antibiotic-resistant gram-negative bacteria. Chest. 2008;134:281-287. 5. Leone M, Garcin F, Bouvenot J, et al. Ventilator-associated pneumonia: breaking the vicious circle of antibiotic overuse. Crit Care Med. 2007;35:379-385. 6. American Thoracic Society; Infectious Diseases Society of America. Guidelines for the management of adults with hospital-acquired, ventilator-associated, and healthcare-associated pneumonia. Am J Respir Crit Care Med. 2005;171:388-416.
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