Chen P, Ruiz RE, Bishai WR; American Society for Microbiology. General Meeting.
Abstr Gen Meet Am Soc Microbiol. 1999 May 30-Jun 3; 99: 653 (abstract no. U-101).
Johns Hopkins School of Hygiene and Public Health, Baltimore, MD.
Previous studies have shown that the Mycobacterium tuberculosis alternative sigma factor, SigF, is regulated at the transcriptional level and that sigF expression increases with stationary phase, anaerobic growth, oxidative stress, and certain antibiotic treatment. To determine whether SigF plays a direct role in stress responses and virulence of M. tuberculosis, we have replaced the wild type (wt) M. tuberculosis sigF gene with a defective, unrevertible, mutant version via homologous recombination. Methods: MICs of various antibiotics for both wt and sigF knock-out (KO) mutant were determined by BACTEC. The virulence of the mutant was examined by intravenously infecting groups of Balb/c mice with approximately 5 X 10(5) organisms. The pathology of infected organs and CFUs from lung and spleen homogenates were followed at various time points. Survival of wt and mutant bacilli were evaluated by the CFU method after stress treatments. Results: The sigF KO mutant was found to be 4 and 2.5 times more susceptible to rifampin and beta-lactam-containing antibiotics, respectively, than the parental wt strain. During mouse infection, the sigF KO mutant proliferated in lung until 8 weeks, but thereafter failed to increase further from weeks 8 to 20. Significantly fewer mutant bacilli survived in both spleens and lungs of infected animals beginning at 2 weeks. The histologic analysis showed that the organs from mutant-infected mice had markedly reduced and delayed inflammation as compared to the wt. The defect in SigF did not affect the survival of the organisms under stationary phase, heat shock, or anaerobic conditions in vitro. However, treatment with cumene hydroperoxide reduced the survival of sigF KO mutant in vitro. Conclusion: The alternative sigma factor, SigF, of M. tuberculosis plays important roles in the development of persistent infection in vivo and in antibiotic resistance.
Publication Types:
Keywords:
- Animals
- Communicable Diseases
- Heat-Shock Response
- In Vitro
- Mice
- Mycobacterium tuberculosis
- Oxidative Stress
- Sigma Factor
- Tuberculosis
- Virulence
Other ID:
UI: 102195836
From Meeting Abstracts