The impact of inadequate disinfection on outbreak of carbapenem-resistant Acinetobacter baumannii in a medical intensive care unit

Abstract

Purpose: This study was conducted to investigation of an outbreak caused by carbapenem-resistant A. baumannii (CRAB) in a medical intensive care unit (ICU) in a regional hospital. Methods: In response to carbapenem-resistant A. baumannii (CRAB) outbreak from October 2012 to February 2013, we developed several infection control measures including extensively review process of environmental cleaning and disinfection, and using molecular methods to identify each clinical and environmental CRAB isolate. Results: During this period of five months, 22 patients had CRAB colonization and 18 patients had CRAB infections. In-hospital mortality was significantly higher among patients with infection than colonization (44.4% vs 9.1%, p Z 0.028). Additionally, nine environmental specimens, including five specimens collected after terminal disinfection, were positive for CRAB. Nine of 12 environmental isolates and 31 of 36 available clinical isolates belong to one unique pulsotype, which was confirmed by molecular methods. We found the concentration of disinfectant sodium hypochlorite was inadequate, which was only 0.08%. After correction for environmental cleansing and aforementioned surveillance study, there was no more CRAB on the control panel surfaces of the medical equipment, and patients in the ICU. Additionally, in vitro study of CRAB against different concentration of sodium hypochlorite showed that 0.5% sodium hypochlorite eradicates CRAB after 30 seconds of inoculation, but 0.08% sodium hypochlorite can only reduce the bacterial load. Conclusions: This study highlights the importance of preparation of disinfectant and adequate environmental disinfection in the control of CRAB outbreak in the ICU.