title: A replication clock for Mycobacterium tuberculosis.
abstract: Few tools exist to assess replication of chronic pathogens during infection. This has been a considerable barrier to understanding latent tuberculosis, and efforts to develop new therapies generally assume that the bacteria are very slowly replicating or nonreplicating during latency. To monitor Mycobacterium tuberculosis replication within hosts, we exploit an unstable plasmid that is lost at a steady, quantifiable rate from dividing cells in the absence of antibiotic selection. By applying a mathematical model, we calculate bacterial growth and death rates during infection of mice. We show that during chronic infection, the cumulative bacterial burden-enumerating total live, dead and removed organisms encountered by the mouse lung-is substantially higher than estimates from colony-forming units. Our data show that M. tuberculosis replicates throughout the course of chronic infection of mice and is restrained by the host immune system. This approach may also shed light on the replication dynamics of other chronic pathogens.
authors.affiliation: Division of Allergy and Infectious Diseases, University of Washington Medical Center, 1959 Northeast Pacific Street, Box 356523, Seattle, Washington 98195, USA.
authors.forename: Wendy P
authors.initials: WP
authors.lastname: Gill
authors.forename: Nada S
authors.initials: NS
authors.lastname: Harik
authors.forename: Molly R
authors.initials: MR
authors.lastname: Whiddon
authors.forename: Reiling P
authors.initials: RP
authors.lastname: Liao
authors.forename: John E
authors.initials: JE
authors.lastname: Mittler
authors.forename: David R
authors.initials: DR
authors.lastname: Sherman
mesh_terms: D000818:Animals; D001483:Base Sequence; D015169:Colony Count, Microbial; D017931:DNA Primers; D051379:Mice; D008810:Mice, Inbred C57BL; D009169:Mycobacterium tuberculosis / Q000254:growth & development*; D010957:Plasmids; D016133:Polymerase Chain Reaction; D014376:Tuberculosis / Q000382:microbiology* / Q000503:physiopathology
chemical_list: D017931:DNA Primers