The approximate mathematical relationship between the prevalence and incidence data of nosocomial infection is confirmed by this study. However, although it is theoretically possible, we would not recommend the conversion of prevalence into incidence data or vice versa.

After checking the situation in one's own hospital, the "either-or" approach using the two indicators "microbiology report" and "antibiotic administration" can be recommended as a time-saving measure to diagnose pneumonia, urinary tract, and primary bloodstream infections. For wound infections, additional information obtained by changing dressings or participating in ward rounds is necessary to achieve satisfactory sensitivity in the surveillance of nosocomial infections. Of course, it is necessary that the surveillance staff discard all false positives to ensure a satisfactory specificity.

This study demonstrates that NI rates can be significantly reduced by appropriate intervention methods in hospitals that are interested in quality management activities. However, continuous intense efforts are necessary to maintain these improvements.

Since it is very time-consuming to follow patients after their transfer from the ICU, we do not perform a postdischarge follow-up of patients in the course of routine surveillance.

The compliance of hand disinfection is similar to other study results, but on some intensive care units there was considerable room for improvement. In this study the compliance of hand hygiene is more of a constant factor in individual intensive care units than associated with the patient/nurse-ratio.