Inhibition of growth ofLegionella species by heterotrophic plate count bacteria isolated from chlorinated drinking water

The ability of heterotrophic plate count bacterial strains isolated from chlorinated drinking water on low-nutrient media to inhibit the growth ofLegionella species was examined. Between 16% and 32% of these strains were able to inhibit the growth ofLegionella species when tested on buffered charcoal yeast extract agar. The exact proportion of inhibiting strains varied with the individualLegionella species. Two strains that inhibited the growth of severalLegionella species could also stimulate the growth of the same species when both the test strain and theLegionella species were grown on buffered charcoal yeast extract agar that lacked the essential amino acidl-cysteine.