Figure 4. Digitized pulsed-field gel electrophoresis (PFGE) patterns and phylogenetic tree of 183 VEB-1–producing Acinetobacter baumannii isolates. Half of A. baumannii isolates from the 4 largest hospitals of 2 districts (59 and 62) were randomly selected over the entire epidemic period; all isolates from smaller hospitals or from other districts were included. The PFGE pattern of the A. baumannii AYE reference strain previously described is indicated in brackets (16). ApaI macrorestriction patterns were digitized and analyzed with Taxotron software (Institut Pasteur, Paris, France) to calculate Dice coefficients of correlation and to generate a dendrogram by the unweighted pair-group method using arithmetic averages clustering. The scale indicates the level of pattern similarity. PFGE results were interpreted according to the criteria of Tenover et al. (25). For a given PFGE pattern, the districts, along with the number of times a given PFGE pattern was found, are also indicated.