Mip genotyping of Legionella isolated from central air-conditioning cooling towers in Guangzhou public places

Abstract:

[Objective] To analyze the genetic characteristics and dominant types of Legionella isolated from central air-conditioning cooling towers in public places in Guangzhou from 2008 to 2010. [Methods] Genomic DNA was extracted from 140 strains of Legionella (119 strains of pneumophila and 21 strains of non-pneumophila). Subsequently, the mip (macrophage infectivity potentiator) gene was PCR amplified, purified and sequenced. Those nucleotide sequences were blasted in the European Working Group for Legionella Infections (EWGLI) Database for the mip typing. Phylogenetic trees were constructed with the Neighbor-Joining (NJ) method using MEGA 5.0. [Results] Approximately 700 bp fragments of the mip gene was obtained from 140 Legionella strains. The 119 L. peumophila were found to be in 10 mip types, with L. pneumophila-phil-1 as the dominant accounting for 52.9% (63/119). The 21 non-L. penumophila from the isolates were found to be in 6 mip types, with L. feeleii-D3131 as the dominant accounting for 47.6% (10/21). [Conclusion] Great diversity was observed among Legionella strains in central air-conditioning cooling towers of Guangzhou public places, while the mip typing techniques used in this study could be used for fast genotyping of Legionella.

Key words:Legionella, Molecular typing, Mip genotyping