ABSTRACT
Objective To identify two suspected Legionella pneumophila (L.pneumophila) strains isolated from environmental water and air conditioning cooling water systems in Guangzhou city.Methods The two strains were identified by their cultural characteristics,biochemical test,Legionella-specific primer PCR identification,PCR-enzymatic digestion analysis,16S rRNA,mip and rpoB gene sequencing analysis.Results The two suspected L.pneumophila isolates were identified as gram-negative bacillus appeared as white colonies on BCYEα-agar after incubation for 48 hours at 36℃.Both isolates were positive for oxidase,gelatinase and hydrolysis of hippurate,and negative for urease activity and nitrate reduction.Their phenotypic characteristics were similar to those of L.pneumophila strains.Results of PCR identification by using Legionella-specific primer were positive.Enzymatic digestion analysis showed that the 226 bp PCR products of two isolates were not digested by Taa Ⅰ.The two strains were classified as Legionella busanensis as indicated by gene sequencing analysis of 16S rRNA,mip and rpoB gene.Conclusion Two L.busanensis strains were first isolated from environmental and air conditioning cooling water systems in China.Due to their biochemical characteristics,L.busanensis strains were commonly misidentified as L.pneumophila,but could be effectively identified by PCR-enzymatic digestion analysis and multiple genes identification.