Antibiotic resistance is a major risk factor for epidemic behavior of Acinetobacter baumannii

OBJECTIVE: To study the presence of bacterial factors in clinical isolates of Acinetobacter species in order to identify markers of epidemic potential . DESIGN: Case-control study. METHODS: Forty-six isolates of Acinetobacter species, including 23 epidemic and 23 sporadic strains from different outbreaks in nine European countrie s, were compared for the presence of the following factors: hemagglutinatio n, presence of capsules and fimbriae, binding to salivary mucins, resistanc e to drying, and antibiogram typing. Genotyping of all strains was performe d by amplified fragment-length polymorphism (AFLP). RESULTS: All outbreak strains except two (91%) were identified as Acinetoba cter baumannii. Binding to salivary mucins and resistance to antibiotics we re significantly associated with epidemic behavior. Antibiogram typing show ed clustering of predominantly A baumannii strains within one group, and th ese strains were significantly more resistant to antibiotics than sporadic strains. AFLP genotyping revealed a great heterogeneity among the different European Acinetobacter strains. Cluster analysis of AFLP fingerprints show ed several small clusters of different A baumannii outbreak strains. AFLP g enotyping could not identify a common epidemic marker within the strains st udied. CONCLUSIONS: Antibiogram typing can be used in routine clinical laboratorie s as a screening method to recognize potentially epidemic A baumannii strai ns. Several other factors were found, both in different outbreaks as well a s in sporadic Acinetobacter isolates. These characteristics were unable to predict epidemic behavior and therefore cannot be used as discriminative ep idemic markers. AFLP genotyping demonstrated no common clonal origin of Eur opean epidemic A baumannii strains. This indicates that any clinical A baum annii isolate with resistance to multiple antibiotics can be a potential no socomial outbreak strain (Infect Control Hosp Epidemiol 2001;22:284-238).