Legionnaires` disease (LD) caused by Legionella pneumphila (Lp) is a significant public health threat in community and hospital settings. The accurate detection, identification and typing of Lp is crucial for control and prevention of the disease but is greatly limited by the heavy reliance on urinary antigen testing and rare recovery of Lp in respiratory samples via culture.
The molecular epidemiology laboratory for Lp, recently established at the MOH to support LD control. In order to overcome current hindrances in LD investigation, the laboratory has successfully adopted international standardised methods for culture independent identification and typing of Lp in respiratory samples. These methods include: (a) multiplex qPCR assay for identification and quantitation of Lp and initial serotyping (sg1 vs. non-sg.1); (b) direct sequence-based typing (SBT) applied on respiratory samples; (c) nested SBT applied on respiratory samples.
Since 2013 the Molecular Epidemiology Laboratory of Legionella has supported the investigation of 65 LD cases in Israel by typing of clinical and environmental strains. Molecular diagnosis of LD was established in 27 of cases. In 19 cases, application of direct or nested SBT was successful in establishing the sequence types (ST) implicated in LD. Lp sg. 1 ST1 was by far the most common phenon identified. Notably, performance of direct/nested SBT has also identified several cases of LD caused infection by a mixture of STs which would have been overlooked using conventional methods.
While bacterial culture remains the gold standard for Lp diagnosis, culture independent methods appear highly useful and informative for supporting the investigation of LD.
