Molecular epidemiology of clinical Acinetobacter baumannii and Acinetobacter genomic species 13TU isolates using a multilocus sequencing typing scheme.

To further expand the limited multilocus sequence typing (MLST) database for Acinetobacter baumannii, 53 clinical isolates from various outbreaks in Europe and the USA, collected between 1991 and 2004, plus the A. baumannii reference strain ATCC 19606(T) and 20 clinical Acinetobacter genomic species 13TU isolates from the same period, were analyzed using a new MLST scheme based on fragments of the gltA, gyrB, gdhB, recA, cpn60, gpi and rpoD genes. Data were compared with typing results generated using pulsed-field gel electrophoresis (PFGE) and randomly amplified polymorphic DNA (RAPD)-PCR. In total, 50 sequence types (STs) were distinguished among the A. baumannii isolates investigated, and the MLST data were in high concordance with the PFGE and RAPD-PCR results. Only five clonal complexes were identified by eBURST analysis, including the 21 STs listed in a previous study, suggesting high diversity among the A. baumannii isolates. With one exception, there was no relatedness among isolates from outbreaks in different countries (Europe) or regions (USA). No intercontinental spread was revealed. Acinetobacter genomic species 13TU isolates could also be analyzed using the A. baumannii MLST scheme (18 different STs) and could be distinguished from A. baumannii isolates according to characteristic sequences. It was concluded that the MLST scheme provides a high level of resolution and is a promising tool for studying the epidemiology of A. baumannii and Acinetobacter genomic species 13TU.