Control of carbapenem-resistant Acinetobacter baumannii outbreak in an intensive care unit of a teaching hospital in Southern Italy

Background: Acinetobacter baumannii is an opportunistic pathogen that has become a major cause of concern, since it is a frequent cause of healthcare-associated infections (HAIs). The aim of the study was to describe the occurrence, the management and the control of an outbreak that occurred in an intensive care unit (ICU) of a teaching hospital in Southern Italy caused by multiple strains of extensively drug-resistant A. baumannii (XDRAB). Methods: Case-patient was defined as a patient with an healthcare-associated infection caused by an XDRAB isolate identified in a clinically significant culture. Environmental samples were collected from different surfaces. The isolates were identified by typical Gram stain morphology, using the Vitek 2 system (bioMerieux, France) and by MALDI-TOF MS mass spectrometry (bioMerieux, France). Genotyping was performed through rep-PCR analysis. Results: A patient presented an XDRAB ventilator-associated pneumonia at admission and was managed with strict isolation precautions until discharge. Five patients had a ventilator-associated pneumonia and two had a central line-associated bloodstream infection. Of the environmental samples, 1 sample obtained from the side of the bed of an infected patient yielded growth of XDRAB. Infection control measures were adopted. Rep-PCR analysis identified four patterns. Conclusions: The integration of epidemiological and microbiological data and the application of infection control measures were crucial to bring such an outbreak to a rapid halt. The distinctive characteristic of this study was the complex molecular pattern of the outbreak, which subsided in a short period of time due to adherence to infection-control measures, confirming the fundamental role of molecular typing in the comprehension of outbreaks dynamics and of integrated control interventions for the interruption of epidemic events.