Lipopolysaccharide chemotypes of Burkholderia cepacia

Burkholderia cepacia is an important pathogen in patients with cystic fibro sis (CF) and much is now known of its epidemiology, In contrast, its virule nce mechanisms are poorly understood. The lipopolysaccharide (LPS) of B, ce pacia, a well-recognised virulence factor of other gram-negative bacteria, is known to be strongly endotoxic in vitro. The aim of this study was to ob serve if there were any links between the structure of B. cepacia LPS and v irulence. This has been investigated by polyacrylamide gel electrophoresis and immunoblotting to define the chemotype and antigenic cross reactivity o f B, cepacia LPS. Strains (16) belonging to different genomovars of the B, cepacia complex were selected to represent epidemic and non-epidemic clinic al isolates and environmental strains. All strains belonging to genomovars I and II (the latter now renamed B, multivorans) had smooth LPS. However, i solates belonging to genomovar III, the group to which most of the epidemic CF isolates belong - including the highly transmissible strain (ET 12) whi ch has been found in both the UK and North America - were of either rough o r smooth LPS chemotype. In this study, B. cepacia J2315 represents the ET 1 2 lineage, and has a rough chemotype. Rabbit antiserum raised to strain J23 15 revealed that the LPS core of this strain was antigenically related to s ome but not all other genomovar III strains, but it also cross-reacted stro ngly with all B, multivorans (genomovar II) and most genomovar I strains. I ntra-strain phenotypic variation was demonstrated between bacteria grown in broth or on solid agar with a concomitant variation in antigenic cross rea ctivity. There was no clear evidence to associate any particular LPS phenot ype with epidemic or non-epidemic strains, but changes in phenotype in vitr o may provide clues to the survival and adaptability of B. cepacia in hosti le environments and possibly to its ability to produce an inflammatory resp onse in vivo.