Emerging Community-Acquired Methicillin-Resistant Staphylococcus Aureus Pneumonia

Background: Methicillin-resistant Staphylococcus aureus (MRSA) has been an important nosocomial pathogen worldwide for more than four decades. Community-acquired MRSA infections, generally occurring in previously healthy persons without recognizable risk factors for health care setting-related MRSA, are emerging as serious clinical and public health concerns. The most frequent of these community-based infections include skin and soft tissue infections and necrotizing pneumonias. A majority of causative community-acquired MRSA (CA-MRSA) isolates are associated with genes that encode the virulence factor, Panton-Valentine leukocidin (PVL) toxin. Aims & Objectives: To describe six cases of CA-MRSA pneumonia recently admitted to our community hospital in Florida, and discuss the epidemiology, clinical features, and management of these expanding infections. Methods/Study Design: The medical records of six patients with radiographically-confirmed pneumonia and positive sputum cultures for MRSA at the time of hospitalization at the Lawnwood Regional Medical Center and Heart Institute, Fort Pierce, Florida, from December 2006 through January 2007, were retrospectively reviewed. All patients were seen by one of the authors (DO), an infectious diseases consultant. Lawnwood Regional Medical Center is a 341-bed, acute care institution and regional referral center for four counties of Treasure Coast, FL. The hospital institution review board gave permission for this study. Results/Findings: Six patients (5 men, 1 woman) with CA-MRSA pneumonia were identified. The mean patient age was 57 years (range, 32-79 years). Three patients had no history of previous hospital admission, while two patients had been last hospitalized two years prior to the study admission. Three elderly patients had known co-morbidities predisposing to pneumonia including carcinoma of the lung (2 patients), and cirrhosis, diabetes mellitus, chronic renal failure, COPD, and cardiomyopathy (1 patient each). Sputum samples were collected at the time of admission and all grew MRSA. Two isolates were resistant only to oxacillin, while four were also resistant to levofloxacin (3 isolates), erythromycin (2 isolates), ciprofloxacin (1 isolate), and/or clindamycin (1 isolate). One patient had concurrent Pseudomonas bacteremia, and another had Pseudomonas isolated from sputum culture in addition to MRSA. All patients had abnormal chest radiographs; three had focal unilateral pneumonia, two had bilateral pneumonia, and one had a lung abscess. The latter patient also had evidence of metastatic infection with sternoclavicular osteomyelitis. Three patients required ventilatory support; two of these subjects died and one was discharged to hospice care. None of the six patients had any epidemiologic connection to one another. Conclusion: CA-MRSA is becoming an increasingly important cause of community-acquired pneumonia in many parts of the world, and in these regions empiric antibiotic treatment guidelines should be reconsidered.