• Staphylococcus aureus infection any time after 5 days of mupirocin ointment
  

• Presence or abscence of risk factors associated with S. aureus infections at any time during the hospital stay
  

In a past study, we showed that there is a strong correlation between strains colonizing the anterior nares, strains isolated from the presumed foci of infection, and strains isolated from blood in patients with Staphylococcus aureus bacteremia. These results suggested that a substantial proportion of cases of systemic S. aureus infections appear to be of endogenous origin and that eradication of nasal colonization should be the chief strategy for reducing the incidence of hospital-acquired S. aureus infections.

In order to evaluate the effect of eliminating nasal carriage by mupirocin prophylaxis on subsequent S. aureus infection, a prospective randomized trial was performed particularly including patients with predisposing risk factors for S. aureus infections. All patients admitted to selected units in clinics for anaesthesiology, hemato-oncology, cardiac surgery, and orthopedics at the University Hospital of Muenster were regularly screened for nasal carriage, i.e. at admission and, subsequently, on a weekly basis. S. aureus carrying patients were prospectively randomized, to be either treated with mupirocin for 5 days, or left untreated. Patients infected with S. aureus at admission and patients detected to be MRSA carrier were excluded from randomization.

Patients were regularly seen during the course of their hospital stay and predisposing/conditional risk factors were systematically documented. In both groups (untreated patients and patients with mupirocin prophylaxis), all nosocomial infections were documented according to CDC guidelines. If infected, specimens were taken for microbiological diagnosis. All S. aureus isolates (from the anterior nares as well as from the focus of infection) were collected and were genotyped.