Variable number tandem repeat loci providing discrimination within widespread genotypes of Acinetobacter baumannii

Some genotypes of Acinetobacter baumannii, defined by pulsed-field gel electrophoresis (PFGE), have been found in many hospitals. Our aim was to find variable number tandem repeat (VNTR) loci capable of providing discrimination among isolates with highly similar or identical PFGE profiles, to gain insights into the epidemiology. Thirteen loci identified in A. baumannii ATCC 17978 were tested using a panel of isolates that included multiple representatives of genotypes belonging to the three European clonal lineages. Two loci, with repeat units of 9 and 6 bp respectively were selected. Repeat numbers varied between 3 and 29, and 9 and 26 respectively at the two loci. The repeat numbers of representatives of each genotype often differed between hospitals, providing a means of tracking patient transfers and possible transmissions between patients. The results suggest that this analysis accurately reflects the known epidemiological information, and provides a valuable tool for cross-infection studies.