The current spectrum of Staphylococcus aureus infection in a tertiary care hospital

Staphylococcus aureus remains a prominent cause of community- and hospital-acquired infection. This study reviewed 162 cases of S. aureus infection occurring in 120 adults who were hospitalized at a Veterans Affairs Medical Center and referred for consultation to the Infectious Disease Service. There were 37 cases of skin and soft tissue infection, 5 pyomyositis, 34 osteomyelitis, 13 septic arthritis, 19 pneumonia, 3 empyema, 5 pyelonephritis, 37 vascular infection, 3 epidural abscess, and 6 miscellaneous infections. Bacteremia was documented in 56 of 119 (47%) cases in which blood cultures were obtained, indicating the serious nature of the infections in many cases. Staphylococcus aureus is widely prevalent in healthy persons. Given its ubiquity and the capacity to cause a broad array of infections, an effective host response must play an important role in preventing infection. This host response is immunologically nonspecific, in that it depends upon the effectiveness of mechanical barriers to invasion and, once invasion takes place, the interaction of PMN, complement, and antibody that is probably present in serum of all immunologically competent adults rather than sensitization of B or T lymphocytes by any identifiable antigens specific to S. aureus. Analysis of the present cases calls attention to S. aureus as an opportunistic pathogen, 1 that only infrequently causes serious infection in otherwise healthy persons. Nearly every patient in this series had 1 or more medical condition thought to predispose to infection; 279 such conditions were identified, representing an average of 2.3 per person. A break in the natural barrier to infection was also present in the majority of cases, for example, trauma, wound, or pre-existing decubitus ulcer in skin and soft tissue infections; endotracheal tube in pneumonia; and a catheter bypassing urethra or skin in urinary and vascular infections, respectively. The tendency for patients to be infected with S. aureus repeatedly (mean number of infections, 1.4 per patient) reflects the chronicity of many predisposing factors and, perhaps, of colonization as well. Staphylococcus aureus has a special predilection to cause infections involving prosthetic devices, perhaps related to its affinity for fibronectin, laminin, and other serum proteins that can mediate attachment to foreign material; 46 of 162 (28%) infections were associated with the presence of a foreign body. Such infections are difficult to eradicate with antibiotic therapy alone, perhaps because of a change in the metabolic state of adherent bacteria, and removal of the foreign body is generally required for cure.(ABSTRACT TRUNCATED AT 400 WORDS)