Isolation of Legionella pneumophila from clinical specimens: salutary effects of lung tissue dilution.

Diagnosis of legionnaires' disease is seldom confirmed by isolation of Legionella pneumophila. In 2 cases, isolates were obtained using inoculums of diluted lung tissue suspension, even though no growth ocurred when undiluted suspensions were used. It is speculated that tissue dilution decreases the concentration of antimicrobial agents and antibacterial properties associated with lung host defense mechanisms, which allows improved recovery rates. This technique is recommended when attempting isolation of L. pneumophila from clinical specimens.