The Reduction of Nosocomial MRSA Infection in Germany An Analysis of Data From the Hospital Infection Surveillance System (KISS) Between 2007 and 2012

Background: Infections with multiresistant Gram negative pathogens are rising around the world, but many European countries have recently seen a decline in infections due to methicillin resistant Staphylococcus aureus (MRSA). We determined the percentage of nosocomial Staphylococcus aureus infections in Germany that were accounted for by MRSA in the past six years and looked for regional differences in the overall downward trend. Methods: Data from the German Hospital Infection Surveillance System (Krankenhaus-Infektions-Surveillance-System, KISS) from the years 2007-2012 were analyzed. In intensive care units, data on the following nosocomial infections were registered: primary sepsis, lower respiratory tract infections, and urinary tract infections; in surgical wards, data on postoperative wound infections were collected. Results: The number of participating intensive care units varied from 465 to 645, while the number of participating surgical wards varied from 432 to 681. Over the period 2007-2012, the percentage of nosocomial Staphylococcus aureus infections that were due to MRSA dropped significantly, from 33% to 27%. More specifically, the percentage of infections due to MRSA dropped from 36% to 31% for primary sepsis and from 36% to 30% for lower respiratory tract infections. Regression analysis revealed significantly lower MRSA fractions in the German states of Brandenburg (odds ratio [OR] 0.41), Bavaria (OR 0.73), and Saxony-Anhalt (OR 0.53), with higher fractions in Berlin (OR 1.59), Mecklenburg-West Pomerania (OR 1.91), Lower Saxony (OR 1.85), and North Rhine-Westphalia (OR 1.55). There were no significant differences in the remaining German states. Conclusion: In Germany, the percentage of nosocomial Staphylococcus aureus infections due to MRSA dropped significantly over the period 2007-2012. The causes of this decline are unclear; it may have resulted from human intervention, pathogen biology, or both.