On the last Wednesday of spring we were spoiled with the room on the top floor of the Australian Museum and magnificent views of Sydney, yes, once again! Joining us were not only our regular JAMS crowd, but also visitors from Europe (yes, that is really cold in Europe during this time of the year!)
Does Acinetobacter baumannii have an O antigen?
Acinetobacter baumannii is amongst the most troublesome Gram-negative pathogens worldwide, due to strains that are resistant to multiple antibiotics, disinfection and periods of desiccation. Little is known about the virulence mechanisms, though a role for capsule has been demonstrated. Previous analysis of A. baumannii genome sequences identified a region of extensive diversity presumed to be involved in the synthesis of a surface polysaccharide, variously identified as O-antigen or capsule. We used bioinformatic tools to assess whether this polysaccharide is exported as capsule, or ligated to a lipid A-core oligosaccharide moiety to become the O antigen moiety of lipopolysaccharide. A gene for O-antigen ligase was not found, and we propose that A. baumannii strains produce a capsule (and lipid A-core oligosaccharide), but no lipopolysaccharide. 9 capsule types and 3 core types were found in the 10 completed genomes and more in draft genomes. Multiple capsule types were found in members of the 2 major clonal complexes, and this variation may contribute to the success of the A. baumannii clones by factoring in the evasion of the host immune response.