Control of a Clonal Outbreak of Multidrug-Resistant Acinetobacter baumannii in a Hospital of the Basque Country after the Introduction of Environmental Cleaning Led by the Systematic Sampling from Environmental Objects
Background. Between July 2009 and September 2010, an outbreak of multidrug-resistant (MDR) Acinetobacter baumannii was detected in one critical care unit of a tertiary hospital in the Basque Country, involving 49 infected and 16 colonized patients. The aim was to evaluate the impact of environmental cleaning and systematic sampling from environmental objects on the risk of infection by MDR A. baumannii. Methods. After systematic sampling from environmental objects and molecular typing of all new MDR A. baumannii strains from patients and environmental isolates, we analyzed the correlation (Pearson’s r) between new infected cases and positive environmental samples. The risk ratio (RR) of infection was estimated with Poisson regression. Results. The risk increased significantly with the number of positive samples in common areas (RR = 1.40; 95%CI = 0.99–1.94) and positive samples in boxes (RR = 1.19; 95%CI = 1.01–1.40). The number of cases also positively correlated with positive samples in boxes ( ; ) and common areas ( ; ). Conclusion. Once conventional measures have failed, environmental cleaning, guided by systematic sampling from environmental objects, provided the objective risk reduction of new cases and enabled the full control of the outbreak. 1. Introduction Acinetobacter baumannii is a ubiquitous, gram-negative and nonfermenting bacillus that can cause both community and healthcare-associated infections due to its antimicrobial resistance, thereby leading to pan-drug resistance and causing large tertiary intrahospital outbreaks, often involving multiple facilities [1]. The multidrug-resistant (MDR) A. baumannii is an opportunistic pathogen that can cause health care-associated infections due to its antimicrobial resistance, resistance to desiccation and capability of surviving on the surfaces of critical areas [2]. The major risk factors for infection include invasive procedures, such as the use of mechanical ventilation, central venous or urinary catheters, and broad-spectrum antimicrobials [3]. In this paper we describe an outbreak of MDR A. baumannii in one of the critical care units of our tertiary hospital in the Basque Country from July 2009 to September 2010. The goal of the study was to analyze the impact of the environmental factors and cleaning measurements taken over the evolution of the outbreak and to interpret these results from an epidemiological point of view. 2. Materials and Methods 2.1. Setting The critical care area where the outbreak arose is subdivided into three units (A1, A2, and A3), with a total of 33 beds, all of
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