Sensitive genus-specific detection of Legionella by a 16S rRNA based sandwich hybridization assay

A high sensitivity was obtained by modifying the probe chemistry and hybridization conditions. The most sensitive assay uses a 3′-end biotin-labelled capture probe and a 3′-end DIG tailed detection probe and has a detection limit of 20 amol target molecules corresponding to 1.2 × 107 molecules of 16S rRNA and approximately 1800 Legionella cells. Using this assay type the number of Legionella cells was determined in Legionella contaminated water samples. The results show that the developed SHA can be applied for estimation of the approximate number of Legionella cells based on the number of 16S rRNA molecules in a water sample.