Shedding of lipopolysaccharide and 200-kDa surface antigen during the in vitro growth of virulent Ara− and avirulent Ara+ Burkholderia pseudomallei

Non-virulent Ara+ B. pseudomallei environmental isolates differ from virulent Ara− clinical isolates by their ability to assimilate -arabinose and the absence of a 200 kDa antigen on their surface. The latter, present only on the Ara− isolates from either clinical or environmental origin, was recently demonstrated by its immunoreactivity with monoclonal antibody (MAb) 5F8. We recently demonstrated that lipopolysaccharide (LPS) from both biotypes were indistinguishable from one another with regard to SDS-PAGE profiles and immunoreactivities with immune sera. In this study, the shedding of LPS and 200-kDa antigen into the culture medium during the in vitro growth of Ara− was compared with that of its Ara+ counterpart, using MAb-based sandwich ELISAs. The results showed that the LPS shedding profiles from the two biotypes were similar to one another. This was in contrast to the situation with the 5F8-reactive antigen. The culture fluid of all Ara− isolates and none of the Ara+ isolates were found to react strongly with the MAb 5F8 during the early log phase of growth. However, during the late stationary phase, a trace amount of the 5F8-reactive material could also be detected in the culture fluid of the Ara+ isolates.