FIG. 1.

Effects of temperature, inoculum size, and strain on multiplication of L. pneumophila in A. castellanii ATCC 30234. The numbers of Legionella cells in amoeba vacuoles after 24 and 48 h of incubation were expressed as percentages of that at 0 h (bacterial number in amoebas when Legionella and amoebas were coincubated for 3 h at 35°C and for a further 1 h with 50 μg/ml of gentamicin). Data are means ± SD. *, P < 0.05; **, P < 0.01. MOI, multiplicity of infection; numbers indicate bacterium/amoeba cell ratios.