Mycobacterium avium is an intracellular pathogen that is associated with di
sseminated infection in acquired immunodeficiency syndrome (AIDS) patients.
Human monocyte-derived macrophages were infected with M. avium strain 101
and a quinolone (Bay y 3118) was used at 8 mu g ml(-1), a concentration tha
t kills growing bacteria but fails to eliminate static organisms. Infected
monolayers were treated with Bay y 3118 for 4 days and viable bacteria obta
ined from the lysis of macrophages were used to infect other macrophages wi
thout passage in media. The procedure was repeated five times, after which
seven different subpopulations that failed to grow within macrophages were
identified. While the DNA fingerprinting confirmed that all came from the s
ame strain: three protein profiles were observed. Static subpopulations wer
e not killed by cytokine-stimulated macrophages, in contrast to the replica
ting subpopulation. Three of the static subpopulation strains were shown to
be auxotrophic for glutamic acid or methionine. All seven non-duplicating
subpopulation strains grew well in complete 7H10 agar. The importance of a
static subpopulation of M. avium within macrophages is presently unknown. I
t is possible, however, that the non-growing bacteria would persist within
macrophages. (C) 1999 Federation of European Microbiological Societies. Pub
lished by Elsevier Science B.V. All rights reserved.