Identification of Acinetobacter baumannii strains with monoclonal antibodies against the O antigens of their lipopolysaccharides

Despite the emergence of Acinetobacter baumannii strains as nosocomial path ogens, simple methods for their phenotypic identification are still unavail able. Murine monoclonal antibodies specific for the O-polysaccharide moiety of the lipopolysaccharide (LPS) of two A. baumannii strains were obtained after immunization with heat-killed bacteria. The monoclonal antibodies wer e characterized by enzyme immunoassay and by Western and dot blot analyses and were investigated for their potential use for the identification of A. baumannii strains. The antibodies reacted with 46 of the 80 A. baumannii cl inical isolates that were investigated, and reactivity was observed with 11 of 14 strains which were isolated during outbreaks in different northweste rn European cities; no reactivity was observed with Acinetobacter strains o f other genomic species, including the closely related genomic species 1 (A cinetobacter calcoaceticus), 3, and 13 sensu Tjernberg and Ursing, or with other gramnegative bacterial strains. The results show that O-antigen-speci fic monoclonal antibodies such as the ones described are convenient reagent s which can be used to identify Acinetobacter strains in clinical and resea rch laboratories.