Legionella dumoffii Tex-KL Mutated in an Operon Homologous to traC-traD is Defective in Epithelial Cell Invasion / 生物医学与环境科学（英文）

<p><b>OBJECTIVE</b>To understand the mechanism of invasion by Legionella dumoffii.</p><p><b>METHODS</b>The L. dumoffii strain Tex-KL was mutated using the Tn903 derivative, Tn903dIIlacZ. After screening 799 transposon insertion mutants, we isolated one defective mutant. We then constructed the gene-disrupted mutant, KL16, and studied its invasion of and intracellular growth in HeLa and A549 cells, and in A/J mice survival experiments. The structure of traC-traD operon was analyzed by RT-PCR.</p><p><b>RESULTS</b>The transposon insertion was in a gene homologous to Salmonella typhi traC, which is required for the assembly of F pilin into the mature F pilus structure and for conjugal DNA transmission. Results from RT-PCR suggested that the traC-traD region formed an operon. We found that when the traC gene was disrupted, invasion and intracellular growth of L. dumoffii Tex-KL were impaired in human epithelial cells. When mice were infected by intranasal inoculation with a traC deficient mutant, their survival significantly increased when compared to mice infected with the wild-type strain..</p><p><b>CONCLUSION</b>Our results indicated that the traC-traD operon is required for the invasion and intracellular growth abilities of L. dumoffii Tex-KL in epithelial cells.</p>

Adhesion, invasion and intracellular growth ability of Legionella dumoffii in alveolar epithelial cells / 中国人兽共患病学报

In this study,the L.dumoffii TEX-KL (ATCC 33343),L.dumoffii NY23 (ATCC 33279) and L.pneumophila philadelphila-1 (ATCC 33155) strains were used to explore the adhesion,invasion and intracellular growth ability in the epithelial cells.Approximately 1× 108 bacteria were pelleted,resuspended,and diluted (1 ∶ 10) in RPMI 1640 tissue culture medium.The bacteria were then added to A549 cells (1 × 105 per well) in 24-well plates to give a multiplicity of infection (MOI) of about 100.The Gimenez staining and colony counting methods were used for the determination of the strain adhesion,invasion and intracellular growth ability.It was found that in vitro growth ability of L.pneumophila philadelphila-1,L.dumoffii TEX-KL and L.dumoffii NY23 strains had no significant difference.For in vivo assay,there was also no significant difference in adhesion ability of these strains.However,the CFU counts of L.dumoffii TEX-KL strain invaded into A549 cells was 1 000 times higher than that of the other two strains.Compared with L.pneumophila philadelphila-1 and L.dumoffii NY23 strains,L.dumoffii TEX-KL strain has higher invasion ability and,therefore,higher intracellular growth ability.