How many outbreaks of nosocomial infections occur in German neonatal intensive care units annually?

Outbreaks on neonatal intensive care units (NICUs) achieve huge media interest, but the real number of neonatal outbreaks within a country is unknown. This calculation is based on the data of the component for nosocomial infections in very low birth weight (VLBW) infants of the German national nosocomial infection surveillance system (NEO-KISS) from 2006 to 2011. Almost all German NICUs caring for VLBW infants participated in this surveillance system. A cluster was defined and an outbreak was assumed when at least two cases of severe neonatal infection (bloodstream infection, pneumonia) occurred within a defined time interval in one center with the same pathogen species in different patients. Four different intervals were used for calculation: 14, 30, 60, and 90 days. Infections with coagulase-negative staphylococci (CoNS) were excluded. A total of 228 NICUs provided data in the six-year study period. A total of 37,038 VLBW infants and 1,361,950 patient days were used for the calculation. 7,405 severe neonatal infections occurred, and a microbiological detection of the pathogen was successful in 2,084 cases. Altogether, between 121 and 280 outbreaks were calculated according to the different time intervals used. Most outbreaks were due to Staphylococcus aureus, followed by Enterococcus spp. and Enterobacter spp. It can be assumed that at least between 26 and 61 neonatal outbreaks with at least two severe infections take place in German NICUs per year. The actual number seems to be higher because only laboratory-confirmed infections in a subgroup of patients were used for the analysis.