[Molecular identification, phylogenic and virulence analysis of a Legionella strain isolated from aquatic...

CD-1 was isolated from aquatic environment, which grew with strict L-cysteine dependence. In this study, we applied molecular methods to identify CD-1, and animal test to understand its virulence.

To identify CD-1 strain, CD-1 strain was tested for genus-specific 16S rRNA of Legionella via PCR amplification, then its rpoB gene was sequenced for phylogenic analysis. To understand the virulence, CD-1 was detected for mip gene, which was an indispensable virulent gene of Legionella. Then, BABL/c mice were infected by CD-1 in different dosages.

For identification, CD-1 was positive for genus-specific 16S rRNA of Legionella, while in the phylogenic tree CD-1 was a sister to Legionella longbeachae with high posterior probability (PP = 1.00). For the virulence analysis, CD-1 was positive for mip gene detection. In the animal test, all mice tested died when the infection dose of CD-1 strain reached 10(7) cfu/mL.

CD-1 strain was identified to be Legionella longbeachae with strong virulence to BALB/c mice. It may be a potential virulent strain to human. This is the first strain of Legionella longbeachae isolated in Sichuan province, and this is the first virulence analysis of Legionella strain isolated from aquatic environment in China.