O-antigen diversity among Acinetobacter baumannii strains from the Czech Republic and Northwestern Europe, as determined by lipopolysaccharide-specific monoclonal antibodies

O-antigen-specific monoclonal antibodies (MAbs) are currently being generat ed to develop an O-serotyping scheme for the genus Acinetobacter and to pro vide potent tools to study the diversity of O-antigens among Acinetobacter strains. In this report, Acinetobacter baumannii strains from the Czech Rep ublic and from two clonal groups identified in Northwestern Europe (termed clones I and II) were investigated for their reactivity with a panel of O-a ntigen-specific MAbs generated against Acinetobacter strains from various s pecies. The bacteria were characterized for their ribotype, biotype, and an tibiotic susceptibility and the presence of the 8.7-kb plasmid pAN1, By usi ng the combination of these typing profiles, the Czech strains could be cla ssified into four previously defined groups (A, Nemec, L, Janda, O, Melter, and L, Dijkshoorn, J, med. Microbiol. 48:287-296, 1999): two relatively ho mogeneous groups of multiresistant strains (termed groups A and R), a heter ogeneous group of other multiresistant strains, and a group of susceptible strains. O-antigen reactivity was observed primarily with MAbs generated ag ainst Acinetobacter calcoaceticus and Acinetobacter baumannii strains. A co mparison of reaction patterns confirmed the previously hypothesized clonal relationship between group A and clone I strains, which are also similar in other properties. The results show that there is limited O-antigen variabi lity among strains with similar geno- and phenotypic characteristics and ar e suggestive of a high prevalence of certain A. baumannii serotypes in the clinical environment. It is also shown that O-antigen-specific MAbs are use ful for the follow-up of strains causing outbreaks in hospitals.