The impact of mouse passaging of Mycobacterium tuberculosis strains prior to virulence testing in the mouse and guinea pig aerosol models.
BACKGROUND
It has been hypothesized that the virulence of lab-passaged Mycobacterium tuberculosis and recombinant M. tuberculosis mutants might be reduced due to multiple in vitro passages, and that virulence might be augmented by passage of these strains through mice before quantitative virulence testing in the mouse or guinea pig aerosol models.


RESULTS
By testing three M. tuberculosis H37Rv samples, one deletion mutant, and one recent clinical isolate for survival by the quantitative organ CFU counting method in mouse or guinea pig aerosol or intravenous infection models, we could discern no increase in bacterial fitness as a result of passaging of M. tuberculosis strains in mice prior to quantitative virulence testing in two animal models. Surface lipid expression as assessed by neutral red staining and thin-layer chromatography for PDIM analysis also failed to identify virulence correlates.


CONCLUSIONS
These results indicate that animal passaging of M. tuberculosis strains prior to quantitative virulence testing in mouse or guinea pig models does not enhance or restore potency to strains that may have lost virulence due to in vitro passaging. It is critical to verify virulence of parental strains before genetic manipulations are undertaken and comparisons are made.
Converse
Paul J
PJ
Department of Medicine, Center for Tuberculosis Research, Johns Hopkins University, Baltimore, Maryland, United States of America. pconvers@jhsph.edu
Eisenach
Kathleen D
KD
Theus
Sue A
SA
Nuermberger
Eric L
EL
Tyagi
Sandeep
S
Ly
Lan H
LH
Geiman
Deborah E
DE
Guo
Haidan
H
Nolan
Scott T
ST
Akar
Nicole C
NC
Klinkenberg
Lee G
LG
Gupta
Radhika
R
Lun
Shichun
S
Karakousis
Petros C
PC
Lamichhane
Gyanu
G
McMurray
David N
DN
Grosset
Jacques H
JH
Bishai
William R
WR
D000336:Aerosols; D000818:Animals; D001431:Bacteriological Techniques / Q000592:standards*; D056084:Genetic Fitness; D006168:Guinea Pigs; D008055:Lipids / Q000032:analysis; D051379:Mice; D023421:Models, Animal; D009169:Mycobacterium tuberculosis / Q000166:cytology / Q000235:genetics / Q000472:pathogenicity*; D012107:Research Design / Q000592:standards; D017384:Sequence Deletion; D012692:Serial Passage; D014376:Tuberculosis / Q000382:microbiology; D014774:Virulence
D000336:Aerosols; D008055:Lipids