engleski

The presence of specific capsule genes among different Legionella longbeachae isolates

The capsule is a complex extracellular polysaccharide structure that represents an important virulence factor of many pathogenic bacteria. Recent analysis of the Legionella longbeachae genome and transcriptome has identified a highly conserved gene cluster encoding proteins that are presumed to be involved in the production of the capsule. L. longbeachae is an emerging pathogen isolated from potting soil which causes respiratory infections mostly in Australia, but there is an increase in the number of sporadic infections worldwide. The mechanisms of its pathogenesis are still not well understood and the investigation of the role of the capsule as a virulence factor could enlighten these processes. In order to investigate the presence of two genes, llo3148 and llo3152, assumed to be involved in the capsular biosynthesis, genetic screens among different strains of L. longbeachae, as well as Legionella spp. were done. The llo3148 gene encodes for CpsB, mannose-1-phosphate guanyltransferase, an enzyme involved in mannose metabolism which is an important component of the capsule, while llo3152 encodes for the capsule polysaccharide export inner membrane protein CtrB, a component of the CtrABCD transporter system. The analysis was performed among 14 different clinical and environmental isolates of L. longbeachae (13 of them belonging to Sg1 and one belonging to Sg2), two strains of L. pneumophila and one strain of L. steigerwaltii, L. micdadei and L. gormanii, respectively. To confirm presence or absence of the capsule, negative staining as well as visualization by electron microscopy was applied. The results revealed that the llo3148 and llo3152 genes were present in all analysed L. longbeachae isolates regardless of the origin of the strains. Negative staining and electron microscopy analysis confirmed the presence of a capsule-like structure surrounding the L. longbeachae isolates. Further molecular and functional analyses will no doubt give interesting insights concerning the role of the capsule in the pathogenesis of Legionella longbeachae infections

capsule; Legionella longbeachae; llo3148 and llo3152 gene

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