Effect of heat and acid decontamination treatments on the recovery of Legionella pneumophila from drinking water using two selective media

Two different decontamination systems, heat and acid, and two isolation med ia, GVPC and MWY agar were tested for the recovery of Legionella pneumophil a from drinking water. The samples were concentrated by filtration through 0.2 mu m polyamide filter and the membranes were resuspended in the origina l water samples. The suspension was divided into three parts: the first was placed in a 50 degrees C water bath, the second was acidified in HCl-KCl s olution and the third did not undergo any treatment. The isolation was made by means of media containing charcoal, yeast extract and glycine with cycl oeximide (GVPC) or vancomycin, polimixinB, anysomicin and dyes (MWY). Heati ng at 50 degrees C for 30 minutes was seen to be the best decontamination s ystem above all when used with GVPC agar. Moreover, with this pretreatment higher counts were obtained both on MWY and GVPC agar. The MWY agar produce d the highest isolatin percentages and the highest counts.