COMPARISON OF 4 DIFFERENT METHODS FOR EPIDEMIOLOGIC TYPING OF ACINETOBACTER-BAUMANNII

A set of 103 epidemiologically well-defined Acinetobacter baumannii is olates obtained from nine hospital outbreaks and 21 unrelated strains were characterized by pulsed-field gel electrophoresis (PFGE) of total genomic DNA digested with ApaI. Among outbreak strains, eight differe nt patterns and five possible variants were identified by PFGE. Result s were compared with those from traditional typing methods such as pla smid profile analysis, antimicrobial susceptibility, and biotyping. Pl asmid analysis revealed six different and two related patterns; one ou tbreak strain lacked plasmids. A total of 16 of the 21 unrelated strai ns harbored plasmids and exhibited unique patterns. Epidemiologically unrelated strains were placed into only two biotypes and had similar a ntimicrobial susceptibility patterns but were clearly distinguished by PFGE. PFGE of A. baumannii chromosomal DNA yielded reproducible and e asily readable results and showed excellent discriminatory power. Howe ver, plasmid profile analysis may provide a cost-effective first step in epidemiological typing of A. baumannii isolates obtained from well- defined hospital outbreaks.