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Infection and Immunity, September 1999, p. 4700-4707, Vol. 67, No. 9
Department of Medicine,
Received 9 March 1999/Returned for modification 7 April
1999/Accepted 18 June 1999
The ability to persist in the host after the establishment of
infection is an important virulence determinant for mycobacteria. Mycobacterium abscessus is a rapidly growing mycobacterial
species which causes a variety of clinical syndromes in humans. We have obtained a rough, wild-type human clinical isolate of M. abscessus (M. abscessus-R) and a smooth, attenuated mutant
(M. abscessus-S) which spontaneously dissociated from the
clinical isolate. We have found that M. abscessus-R is able
to persist and multiply in a murine pulmonary infection model in
contrast to M. abscessus-S, which is rapidly cleared. To
understand the basis for this difference, we characterized the behavior
of these variants in human tissue culture models of infection. M. abscessus-R is able to persist and multiply in human monocytes,
while M. abscessus-S is deficient in this ability. Both of
these variants are phagocytized by human monocytes. M. abscessus-R resides in a phagosome typical for pathogenic mycobacteria with a tightly adherent phagosomal membrane. In contrast, M. abscessus-S resides in a "loose" phagosome with the
phagosomal membrane separated from the bacterial cell wall. Both
M. abscessus variants also have distinctive growth patterns
in a recently described fibroblast-mycobacterium microcolony assay,
with M. abscessus-R exhibiting growth characteristics
similar to those previously reported for virulent M. tuberculosis and M. abscessus-S exhibiting growth
characteristics similar to those previously reported for avirulent
M. tuberculosis. In both the monocyte infection assay and
the murine pulmonary infection model, numerous infected mononuclear phagocyte aggregates develop at sites of M. abscessus-R
infection, but are absent with M. abscessus-S infection. We
conclude that a mutation has occurred in the M. abscessus-S
variant which has altered the ability of this organism to persist and
multiply in host cells and that this may be related to the phenotypic
changes we have observed in our tissue culture models of infection.
0019-9567/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.
Preliminary Characterization of a
Mycobacterium abscessus Mutant in Human and Murine Models
of Infection
*
Corresponding author. Mailing address: Department of
Medicine (111J), Albuquerque Veterans Affairs Medical Center, 1501 San Pedro, SE, Albuquerque, NM 87108. Phone: (505) 265-1711, extension 2488. Fax: (505) 256-2803. E-mail: tfbyrd{at}pol.net.
Infection and Immunity, September 1999, p. 4700-4707, Vol. 67, No. 9
0019-9567/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.
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