THE CONSTRUCTION AND CHARACTERIZATION OF COLANIC ACID-DEFICIENT MUTANTS IN AN EXTRAINTESTINAL ISOLATE OF ESCHERICHIA-COLI (O4 K54/H5)/

Extraintestinal strains of Escherichia coil possess a variety of virul ence factors that enable them to cause disease. These strains express a group 2 capsular polysaccharide which is important in the pathogenic process. Extraintestinal strains evaluated to date are also capable o f producing the group 1 capsular polysaccharide colanic acid. The bloo d isolate CP9 (O4/K54/H5) constitutively produces the group 2, K54 cap sule but can be induced to produce colanic acid. In this report we ass ess whether colanic acid contributes to the pathogenesis of this extra intestinal pathogen. CP9 and its derivatives that are deficient in the ir ability to produce colanic acid (TR94), the K54 group 2 capsule +/- colanic acid (CP9.137, TR1374) and the O4 specific antigen +/- colani c acid (CP921,CP925) were used to test whether the group 1 capsule col anic acid conferred protection against the bactericidal effects of ser um and recombinant bactericidal/permeability-increasing protein (rBPI- 23) in vitro. Additionally, CP9, CP9.137 and TR94 were evaluated in th e rat granuloma pouch, an in vivo model for localized infection, and. by intraperitoneal inoculation into mice, a systemic infection model. In summary, the inability of CP9 to produce colanic acid in the presen ce or absence of its K54 and O4 antigens had no effect on its ability to survive these host defenses in vitro and did not affect its virulen ce in these two in vivo models of infection.