Evaluation of the usefulness of a new direct immunofluorescence assay (ScanVIT-Legionella[trade mark sign]) for monitoring hospital water systems contaminated with Legionella spp

To compare the efficiency of the ScanVIT-Legionella[trade mark sign] test (Vermicon, Munich, Germany) vs a conventional culture method for the quantification of Legionella spp. in hospital water samples in daily hospital practice. The detection of Legionella spp. takes place on a cultivated filter brought into contact with dye-marked gene probes. The results are analysed under fluorescence microscopy. Bacteria that light up green belong to the genus Legionella; those that light up both green and red belong to the species Legionella pneumophila. Our results showed that the ScanVIT test has a sensitivity of 90%; agreement between the two methods was 82%. In the 48 samples that tested positive with both methods, the Legionella concentration detected by the culture method was consistently higher. A statistically significant difference between the results obtained with the two test methods emerged at the Wilcoxon test (P < 0·001). The ScanVIT test may be recommended for investigating the presence of Legionella by qualitative testing. Given the simplicity of colony identification by fluorescence, the ScanVIT test can be used in laboratories where staffs are not experienced in identifying typical colonies of Legionella.