An Epidemiological Investigation of a Nosocomial Outbreak of Multidrug-resistant Acinetobacter baumannii in a Critical Care Center in Japan, 2011–2012

Abstract

In 2011, a multidrug-resistant Acinetobacter baumannii (MDRAB) outbreak occurred at a critical care center (CCC) in a tertiary hospital in Japan. Multidrug-resistance is defined as resistance to amikacin, carbapenem, and fluoroquinolone. We conducted an epidemiological investigation of this outbreak to identify risk factors for MDRAB respiratory tract acquisition in this hospital. A case was defined as a hospitalized patient whose culture was MDRAB positive at least 3 days after admission to the CCC between June 1, 2011 and April 20, 2012. Fifteen MDRAB cases were identified, including three with infection and 12 with colonization. This case–control study demonstrated that hypoalbuminemia and carbapenem administration were associated with MDRAB respiratory tract acquisition. Pulsed-field gel electrophoresis analysis and multilocus sequence typing using MDRAB isolates suggested a clonal dissemination of MDRAB strain with sequence type 74 among patients admitted primarily to the CCC. Introduction of control measures from April 16, 2012, including the closure of the emergency room and interruption of admission to the CCC, isolation of patients with MDRAB colonization or infection within a single room, and environmental cleaning, decreased the isolation rate of MDRAB in the hospital. No MDRAB case was detected between March 23 and April 20, 2012.