Grouping of 20 reference strains of Legionella species by the growth ability within mouse and guinea pig macrophages

20 Reference strains of Legionella species, isolated from human, were class ified according to their ability to grow within thioglycolate-induced perit oneal macrophages of mice and guinea pigs. inbred and congenic mice were us ed to study the effect of the natural resistance genes Lgn1 and Bcg that ar e expressed phenotypically in the mouse macrophages. The Lgn1 gene controll ed the intracellular growth of Legionella pneumophila Philadelphia-1 and Le gionella jordanis GIFU 12657, but the Bcg gene did not affect the intracell ular growth of any organism examined. Based on these results and the growth ability in guinea pig macrophages, the 20 reference strains were divided i nto four groups. This grouping will help us to understand a variety of mode s of interaction between Legionella species and macrophages. (C) 1999 Feder ation of European Microbiological Societies. Published by Elsevier Science B.V. All rights reserved.