Exploring anti-bacterial compounds against intracellular Legionella.
Legionella pneumophila is a ubiquitous fresh-water bacterium which reproduces within its erstwhile predators, environmental amoeba, by subverting the normal pathway of phagocytosis and degradation. The molecular mechanisms which confer resistance to amoeba are apparently conserved and also allow replication within macrophages. Thus, L. pneumophila can act as an 'accidental' human pathogen and cause a severe pneumonia known as Legionnaires' disease. The intracellular localisation of L. pneumophila protects it from some antibiotics, and this fact must be taken into account to develop new anti-bacterial compounds. In addition, the intracellular lifestyle of L. pneumophila may render the bacteria susceptible to compounds diminishing bacterial virulence and decreasing intracellular survival and replication of this pathogen. The development of a single infection cycle intracellular replication assay using GFP-producing L. pneumophila and Acanthamoebacastellanii amoeba is reported here. This fluorescence-based assay allows for continuous monitoring of intracellular replication rates, revealing the effect of bacterial gene deletions or drug treatment. To examine how perturbations of the host cell affect L. pneumophila replication, several known host-targeting compounds were tested, including modulators of cytoskeletal dynamics, vesicle scission and Ras GTPase localisation. Our results reveal a hitherto unrealized potential antibiotic property of the β-lactone-based Ras depalmitoylation inhibitor palmostatin M, but not the closely related inhibitor palmostatin B. Further characterisation indicated that this compound caused specific growth inhibition of Legionella and Mycobacterium species, suggesting that it may act on a common bacterial target.
Max von Pettenkofer Institute, Ludwig-Maximilians University, Munich, Germany.
Christopher F
CF
Harrison
Sébastien
S
Kicka
Valentin
V
Trofimov
Kathrin
K
Berschl
Hajer
H
Ouertatani-Sakouhi
Nikolaus
N
Ackermann
Christian
C
Hedberg
Pierre
P
Cosson
Thierry
T
Soldati
Hubert
H
Hilbi
D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D002460:Cell Line; D049452:Green Fluorescent Proteins / Q000378:metabolism; D006801:Humans; D020128:Inhibitory Concentration 50; D042541:Intracellular Space / Q000187:drug effects / Q000382:microbiology*; D016952:Legionella pneumophila / Q000187:drug effects* / Q000254:growth & development; D051379:Mice; D008826:Microbial Sensitivity Tests; D008970:Molecular Weight; D009161:Mycobacterium / Q000187:drug effects / Q000254:growth & development; D011420:Propiolactone / Q000031:analogs & derivatives / Q000494:pharmacology; D013045:Species Specificity; D013450:Sulfones / Q000494:pharmacology
D000900:Anti-Bacterial Agents; D013450:Sulfones; C578782:palmostatin B; C578783:palmostatin M; D049452:Green Fluorescent Proteins; D011420:Propiolactone