Strain-related virulence of the dominant Mycobacterium tuberculosis strain in the Canadian province of Manitoba.
METHODS
The Canadian province of Manitoba.


OBJECTIVE
To confirm the putative hypervirulence observed in Mycobacterium tuberculosis Type1 strain and further characterize the progression and manifestation of pulmonary tuberculosis caused by this strain in comparison to other common clinical isolates from Manitoba.


METHODS
C3H and BALB/c mice were exposed to aerosols either of Type1, Type2, Type5, Type72 or H37Rv strain to study their respective survival profiles. Additionally, bacillary loads and lung histology were examined at 15 days post-exposure.


RESULTS
In both mouse models, Type-1 infected mice succumbed to disease significantly earlier than other strains (p < or =0.0002). Differences between average log(10) CFU values between clinical isolates were less than 1log(10) difference. In C3H mice, the amount of granulomatous inflammation was highest in Type1 infected mice but not significantly different than all clinical strains. In contrast, BALB/c mice infected with Type1 induced the lowest amount of granulomatous inflammation compared to other clinical isolates.


CONCLUSIONS
Our results indicate that although mice infected with the Type1 strain died significantly earlier than mice infected with other clinical strains in both C3H and BALB/c mice, the hypervirulence of the Type1 strain is not attributed to the growth rate of the organism, as differences in growth between clinical M. tuberculosis isolates were insignificant.
Petrelli
D
D
National Microbiology Laboratory, National Reference Centre for Mycobacteriology, Health Canada, Room H3420 1015 Arlington St, Winnipeg, Manitoba, Canada R3E 3R2. dennis_petrelli@hc-sc.gc.ca
Kaushal Sharma
M
M
Wolfe
J
J
Al-Azem
A
A
Hershfield
E
E
Kabani
A
A
D000818:Animals; D003114:Colony-Forming Units Assay; D005260:Female; D006801:Humans; D008350:Manitoba; D051379:Mice; D008807:Mice, Inbred BALB C; D008809:Mice, Inbred C3H; D023421:Models, Animal; D009169:Mycobacterium tuberculosis / Q000235:genetics / Q000472:pathogenicity*; D013045:Species Specificity; D014397:Tuberculosis, Pulmonary / Q000382:microbiology / Q000635:transmission*; D014774:Virulence