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Appl. Environ. Microbiol., Apr 1997, 1219-1224, Vol 63, No. 4
B Neumeister, S Schoniger, M Faigle, M Eichner and K Dietz
Survival and distribution of legionellae in the environment are assumed to
be associated with their multiplication in amoebae, whereas the ability to
multiply in macrophages is usually regarded to correspond to pathogenicity.
Since most investigations focused on Legionella pneumophila serogroup 1, we
examined the intracellular multiplication of different Legionella species
in Mono Mac 6 cells, which express phenotypic and functional features of
mature monocytes, and in Acanthamoeba castellanii, an environmental host of
Legionella spp. According to the bacterial doubling time in Mono Mac 6
cells and in A. castellanii, seven clusters of legionellae could be defined
which could be split further with regard to finer differences. L.
longbeachae serogroup 1, L. jordanis, and L. anisa were not able to
multiply in either A. castellanii or Mono Mac 6 cells and are members of
the first cluster. L. dumoffi did not multiply in Mono Mac 6 cells but
showed a delayed multiplication in A. castellanii 72 h after infection and
is the only member of the second cluster. L. steigerwaltii, L. gormanii, L.
pneumophila serogroup 6 ATCC 33215, L. bozemanii, and L. micdadei showed a
stable bacterial count in Mono Mac 6 cells after infection but a decreasing
count in amoebae. They can be regarded as members of the third cluster. As
the only member of the fourth cluster, L. oakridgensis was able to multiply
slight in Mono Mac 6 cells but was killed within amoebae. A strain of L.
pneumophila serogroup 1 Philadelphia obtained after 30 passages on SMH agar
and a strain of L. pneumophila serogroup 1 Philadelphia obtained after
intraperitoneal growth in guinea pigs are members of the fifth cluster,
which showed multiplication in Mono Mac 6 cells but a decrease of bacterial
counts in A. castellanii. The sixth cluster is characterized by
intracellular multiplication in both host cell systems and consists of
several strains of L. pneumophila serogroup 1 Philadelphia, a strain of L.
pneumophila serogroup 2, and a fresh clinical isolate of L. pneumophila
serogroup 6. Members of the seventh cluster are a strain of agar- adapted
L. pneumophila serogroup 1 Bellingham and a strain of L. pneumophila
serogroup 1 Bellingham which was passaged fewer than three times on BCYE
alpha agar after inoculation and intraperitoneal growth in guinea pigs. In
comparison to members of the sixth cluster, both strains showed a slightly
enhanced multiplication in Mono Mac 6 cells but a reduced multiplication in
amoebae. From our investigations, we could demonstrate a correlation
between prevalence of a given Legionella species and their intracellular
multiplication in Mono Mac 6 cells. Multiplication of members of the genus
Legionella in A. castellanii seems to be dependent on mechanisms different
from those in monocytes.
Copyright © 1997, American Society for Microbiology
Multiplication of different Legionella species in Mono Mac 6 cells and in Acanthamoeba castellanii
Abteilung Medizinische Mikrobiologie und Hygiene, Universitat Ulm, Germany.
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