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Appl. Environ. Microbiol., 05 1997, 2047-2053, Vol 63, No. 5
M Steinert, L Emody, R Amann and J Hacker
Legionella pneumophila is an aquatic bacterium and is responsible for
Legionnaires' disease in humans. Free-living amoebae are parasitized by
legionellae and provide the intracellular environment required for the
replication of this bacterium. In low-nutrient environments, however, L.
pneumophila is able to enter a non-replicative viable but nonculturable
(VBNC) state. In this study, L. pneumophila Philadelphia I JR 32 was
suspended in sterilized tap water at 10(4) cells/ml. The decreasing number
of bacteria was monitored by CFU measurements, acridine orange direct count
(AODC), and hybridization with 16S rRNA- targeted oligonucleotide probes.
After 125 days of incubation in water, the cells were no longer culturable
on routine plating media; however, they were still detectable by AODC and
by in situ hybridization. The addition of Acanthamoeba castellanii to the
dormant bacteria resulted in the resuscitation of L. pneumophila JR 32 to a
culturable state. A comparison of plate-grown legionellae and reactivated
cells showed that the capacity for intracellular survival in human
monocytes and intraperitoneally infected guinea pigs, which is considered a
parameter for virulence, was not reduced in the reactivated cells. However,
reactivation of dormant legionellae was not observed in the animal model.
Copyright © 1997, American Society for Microbiology
Resuscitation of viable but nonculturable Legionella pneumophila Philadelphia JR32 by Acanthamoeba castellanii
Institut fur Molekulare Infektionsbiologie, University of Wurzburg, Germany.
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