Evaluation of the usefulness of a new direct immunofluorescence assay (ScanVIT-Legionella^™) for monitoring hospital water systems contaminated with<i>Legionella</i>spp.

Abstract

AIMS: To compare the efficiency of the ScanVIT-Legionella test (Vermicon, Munich, Germany) vs a conventional culture method for the quantification of Legionella spp. in hospital water samples in daily hospital practice. METHODS AND RESULTS: 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). CONCLUSION: The ScanVIT test may be recommended for investigating the presence of Legionella by qualitative testing. SIGNIFICANCE AND IMPACT OF THE STUDY: 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.