Chapter 7 : Resistance of Legionella pneumophila to Cationic Antimicrobial Peptides

Intracellular infection with L. pneumophila strains. (A) U937 cell monolayers (n = 3) were infected at a multiplicity of infection (MOI) of 1 with strain 130b (●) and NU260 (□). Asterisks indicate significant differences (P < 0.01; Student's t test) in numbers of recovered bacteria between 130b and NU260. (B) Monolayers of H. vermijormis amoebae (n = 3) were infected with wild-type 130b (●) and mutant NU260 (□) at an MOI of 0.01. Asterisks indicate significant differences (P < 0.05 at 48 h or 0.005 at 72 h; Student's t test). Comparable results were obtained in triplicate experiments, and the data presented here are from one representative experiment.

Growth of L. pneumophila strains in low-Mg2+ liquid medium. Wild-type strain 130b (●) and mutant NU260 (□) were compared for growth in CDM (A), and CDM with 0.005 mM Mg2+ cations (B). Growth was assessed by measuring the optical density at 660 nm of triplicate cultures at various times of incubation. Asterisks indicate significant (P < 0.05; Student's t test) differences between the 130b and NU260 cultures. Standard deviations are shown, but the error bars are too small to be observed in panels A and B. This experiment was performed in triplicate with comparable results and representative data are presented here.