Identification of Genes Required for Chronic Persistence ofBrucella abortusin Mice

• DOI: 10.1128/iai.68.7.4102-4107.2000
• Publication Date: 2002-07-27T10:03:59Z
• Authors: Priscilla C. Hong; Renée M. Tsolis; Thomas A. Ficht
• Keywords: 0301 basic medicine; Mice, Inbred BALB C; Base Sequence; Virulence; Brucella abortus; Brucellosis; 3. Good health; Mice; Mutagenesis, Insertional; 03 medical and health sciences; Genes, Bacterial; Chronic Disease; Gene Targeting; Mutation; Animals; Humans; Cattle; DNA Primers

ABSTRACTThe genetic basis for chronic persistence ofBrucella abortusin lymphoid organs of mice, cows, and humans is currently unknown. We identifiedB. abortusgenes involved in chronic infection, by assessing the ability of 178 signature-tagged mutants to establish and maintain persistent infection in mice. Each mutant was screened for its ability to colonize the spleens of mice at 2 and 8 weeks after inoculation. Comparison of the results from both time points identified two groups of mutants attenuated for chronic infection in mice. The first group was not recovered at either 2 or 8 weeks postinfection and was therefore defective in establishing infection. Mutants in this group carried transposon insertions in genes involved in lipopolysaccharide biosynthesis (wbkA), in aromatic amino acid biosynthesis, and in type IV secretion (virB1andvirB10). The second group, which was recovered at wild-type levels 2 weeks postinfection but not 8 weeks postinfection was able to establish infection but was unable to maintain chronic infection. One mutant in this group carried a transposon insertion in a gene with homology togcvBofMycobacterium tuberculosis, encoding glycine dehydrogenase, an enzyme whose activity is increased during the state of nonreplicating persistence. These results suggest that some mechanisms for long-term persistence may be shared among chronic intracellular pathogens. Furthermore, identification of two groups of genes, those required for initiating infection and those required only for long-term persistence, suggests thatB. abortususes distinct sets of virulence determinants to establish and maintain chronic infection in mice.