Outbreak of multiresistant Acinetobacter baumannii in a polyvalent intensive care unit: clinical, epidemiological analysis and PFGE-printing evolution

An outbreak of multidrug-resistant Acinetobacter baumannii (MRAB) occurred over the course of a 27-week period in our adult polyvalent intensive care unit (ICU). Twenty-one patients were affected, and 72 strains were identified from different clinical samples. The strains were resistant to all antibiotics except for colistin and ampicillin/sulbactam. Forty-nine MRAB strains collected from 18 patients were analysed by pulsed-field gel electrophoresis (PFGE). This analysis revealed four highly-related PFGE types (genetic similarity index >90%) termed 1, 2, 3 and 4, that were isolated in 13, seven, one, and three patients, respectively. A single PFGE type was identified from five of ten patients with successive isolation of MRAB; in the other five patients, two or three PFGE types were detected. This suggested phased evolution of PFGE types 2, 3 and 4 from PFGE type 1. Global mortality was high (13 patients; 62%). Non-survivors had higher APACHE II scores than survivors on the date that MRAB was isolated (OR = 1.57; 95% CI [1.02, 2.44]). The outbreak was controlled after implementation of an extensive infection control program.