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Infection and Immunity, March 2000, p. 1297-1303, Vol. 68, No. 3
INSERM U431, Faculté de Médecine,
30900 Nîmes, France
Received 7 October 1999/Returned for modification 22 November
1999/Accepted 6 December 1999
Bacteria of the genus Brucella are facultative
intracellular pathogens which have developed the capacity to survive
and multiply in professional and nonprofessional phagocytes. The
genetic basis of this aspect of Brucella virulence is still
poorly understood. To identify new virulence factors, we have adapted
signature-tagged transposon mutagenesis, which has been used
essentially in animal models, to an in vitro human macrophage infection
model. A library of 1,152 Brucella suis 1330 tagged
mini-Tn5 Km2 mutants, in 12 pools, was screened for
intracellular survival and multiplication in vitamin
D3-differentiated THP1 cells. Eighteen mutants were identified, and their attenuation was confirmed in THP1 macrophages and
HeLa cells. For each avirulent mutant, a genomic fragment containing
the transposon was cloned. The genomic DNA sequence flanking the
transposon allowed us to assign functions to all of the inactivated
genes. Transposon integration had occurred in 14 different genes, some
of which were known virulence genes involved in intracellular survival
or biosynthesis of smooth lipopolysaccharide (the virB
operon and manB), thus validating the model. Other genes identified encoded factors involved in the regulation of gene expression and enzymes involved in biosynthetic or metabolic pathways. Possible roles in the virulence of Brucella for the
different factors identified are discussed.
0019-9567/00/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.
Identification of Brucella suis Genes
Affecting Intracellular Survival in an In Vitro Human Macrophage
Infection Model by Signature-Tagged Transposon
Mutagenesis
*
Corresponding author. Mailing address: INSERM U431,
Faculté de Médecine, Avenue Kennedy, 30900 Nîmes,
France. Phone: (33) 4 66 23 48 99. Fax: (33) 4 66 23 49 28. E-mail:
docallaghan{at}zeus.sc.univ-montpl.fr.
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