The type II O-antigenic polysaccharide moiety of Burkholderia pseudomallei lipopolysaccharide is required for serum resistance and virulence.
Melioidosis, an infection caused by the gram-negative bacterial pathogen Burkholderia pseudomallei, is endemic in south-east Asia and northern Australia. Acute septicaemic melioidosis is a major cause of morbidity and mortality, especially in north-east Thailand. B. pseudomallei is highly resistant to the bactericidal activity of normal human serum (NHS), and we have found that B. pseudomallei 1026b multiplies in 10-30% NHS. We developed a simple screen for the identification of serum-sensitive mutants based on this novel phenotype. Approximately 1200 Tn5-OT182 mutants were screened, and three serum-sensitive mutants were identified. The type II O-antigenic polysaccharide (O-PS) moiety of lipopolysaccharide was not present in the serum-sensitive mutants. A representative serum-sensitive mutant, SRM117, was killed by the alternative pathway of complement and was less virulent than 1026b in three animal models of melioidosis. The Tn5-OT182 integrations in the serum-sensitive mutants were physically linked on the B. pseudomallei chromosome, and further genetic analysis of this locus revealed a cluster of 15 genes required for type II O-PS production. The proteins encoded by these genes were similar to proteins involved in bacterial polysaccharide biosynthesis. The results presented here demonstrate that type II O-PS is essential for B. pseudomallei serum resistance and virulence.
DeShazer
D
D
Department of Microbiology and Infectious Diseases, University of Calgary Health Sciences Centre, Alberta, Canada.
Brett
P J
PJ
Woods
D E
DE
D051103:1-Acylglycerol-3-Phosphate O-Acyltransferase; D000217:Acyltransferases; D000818:Animals; D001483:Base Sequence; D001770:Blood Bactericidal Activity; D016957:Burkholderia pseudomallei / Q000235:genetics / Q000472:pathogenicity* / Q000502:physiology*; D002237:Carbohydrate Dehydrogenases; D003165:Complement System Proteins / Q000276:immunology; D006224:Cricetinae; D004269:DNA, Bacterial; D004195:Disease Models, Animal; D005260:Female; D005798:Genes, Bacterial; D006168:Guinea Pigs; D006801:Humans; D008554:Melioidosis / Q000382:microbiology; D008647:Mesocricetus; D008969:Molecular Sequence Data; D005810:Multigene Family; D019081:O Antigens; D051381:Rats; D017207:Rats, Sprague-Dawley; D012709:Serum Albumin / Q000276:immunology; D013329:Structure-Activity Relationship; D014774:Virulence