Association between the presence of the Panton-Valentine leukocidin-encoding gene and a lower rate of survival among hospitalized pulmonary patients with staphylococcal disease.

Staphylococcus aureus is responsible for more than 2% of cases of community-acquired pneumonia and 10% of cases of nosocomial-acquired pneumonia. The lethality rate of such infections ranges from 30% to 80% (6). These infections are complicated by the fact that these bacteria have acquired diverse genetic information that makes them resistant to most antibiotics. Methicillin-resistant S. aureus (MRSA) is the most common cause of serious hospital-acquired infections (1). Infections of the respiratory tract by S. aureus can be more severe if the infecting strain produces the Panton-Valentine leukocidin (PVL) (9). The serious impact of PVL-positive S. aureus infections seems to be associated with pulmonary complications. We hypothesized that PVL-positive MRSA is associated with mortality in patients with S. aureus pneumonia. During a period of 12 months, all of the hospital-acquired MRSA isolates recovered from individual patients in the pulmonary ward at the NS Candelaria University Hospital were included in this study. MRSA isolates were considered hospital acquired if they were recovered from a specimen collected 72 h or more after admission to the hospital. A collection of 24 MRSA isolates was characterized by different molecular techniques (3, 7, 8). Cases were analyzed to assess the association between PVL and death in patients affected by different pulmonary diseases and comorbidity charge summarized in the modified Charlson combined index (2). Computerized tomography analysis was also performed when necessary. The concordant diagnosis of pneumonia was determined by chart review by two independent, blinded pulmonologists. Pneumonia or bronchitis was defined by signs and symptoms of lower respiratory tract infection and chest radiography. After detection of MRSA, antibiotic treatment was guided by the antibiotic susceptibility results generated with the Vitek 2 system (bi-