Heat Treatment as an Aid for the Isolation of Legionella pneumophila from Clinical and Environmental Samples

The isolation of legionella's from clinical as well as environmental samples is hindered by the overgrowth of legionella's by the accompanying bacterial flora, which could not be sufficiently suppressed by adding antimicrobial drugs to the BCYAα. The effect of heat treatment on clinical samples and on water samples concentrated by filtration was investigated. Treatment of the samples for 30 minutes at 50 °C reduced the number of cfu of the accompanying flora by a factor 10 1.6-10 3.9 depending on the number of contaminants, whereas the number of cfu of legionella was reduced only by a factor 1.05–1.44. Higher or lower temperatures resulted in a too high reduction of the number of legionella's or an insufficient elimination of the accompanying flora respectively. The described method is less laborious and less critical than the earlier described low pH-treatment.