title: Individual units rather than entire hospital as the basis for improvement: the example of two Methicillin resistant Staphylococcus aureus cohort studies.
abstract: BACKGROUND
  Two MRSA surveillance components exist within the German national nosocomial infection surveillance system KISS: one for the whole hospital (i.e. only hospital based data and no rates for individual units) and one for ICU-based data (rates for each individual ICU). The objective of this study was to analyze which surveillance system (a hospital based or a unit based) leads to a greater decrease in incidence density of nosocomial MRSA METHODS: Two cohort studies of surveillance data were used: Data from a total of 224 hospitals and 359 ICUs in the period from 2004 to 2009. Development over time was described first for both surveillance systems. In a second step only data were analyzed from those hospitals/ICUs with continuous participation for at least four years. Incidence rate ratios (IRR) with 95% confidence intervals were calculated to compare incidence densities between different time intervals.
  
  
  RESULTS
  In the baseline year the mean MRSA incidence density of hospital acquired MRSA cases was 0.25 and the mean incidence density of ICU-acquired MRSA was 1.25 per 1000 patient days. No decrease in hospital-acquired MRSA rates was found in a total of 111 hospitals with continuous participation in the hospital- based system. However, in 159 ICUs with continuous participation in the unit-based system, a significant decrease of 29% in ICU-acquired MRSA was identified.
  
  
  CONCLUSIONS
  A unit-based approach of surveillance and feedback seems to be more successful in decreasing nosocomial MRSA rates, compared to a hospital-based approach. Therefore each surveillance system should provide unit-based data to stimulate activities on the unit level.
authors.affiliation: Institute of Hygiene and Environmental Medicine Charité-University Hospital Berlin, Hindenburgdamm 27, 12203 Berlin, Germany. Petra.Gastmeier@charite.de.
authors.forename: Petra
authors.initials: P
authors.lastname: Gastmeier
authors.forename: Frank
authors.initials: F
authors.lastname: Schwab
authors.forename: Iris
authors.initials: I
authors.lastname: Chaberny
authors.forename: Christine
authors.initials: C
authors.lastname: Geffers