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Virulence of Mycobacterium tuberculosis CDC1551 and H37Rv in rabbits evaluated by Lurie's pulmonary tubercle count

W R Bishai1, A M Dannenberg, N Parrish

  • 1Department of Molecular Microbiology and Immunology, School of Hygiene and Public Health, The Johns Hopkins University, Baltimore, Maryland, USA.

Infection and Immunity
|August 24, 1999
PubMed

Insights

The CDC1551 strain of Mycobacterium tuberculosis showed lower virulence than H37Rv in rabbits. This suggests increased transmissibility, not virulence, caused a localized outbreak.

Area of Science:

  • Microbiology
  • Infectious Diseases
  • Tuberculosis Research

Background:

  • Mycobacterium tuberculosis (M.tb.) is a significant human pathogen.
  • The H37Rv strain is a standard laboratory reference strain for M.tb. virulence studies.
  • The CDC1551 strain has been associated with outbreaks in specific geographic regions.

Purpose of the Study:

  • To compare the virulence of the M.tb. CDC1551 strain against the H37Rv strain.
  • To investigate the factors contributing to the spread of the CDC1551 M.tb. strain.

Main Methods:

  • Utilized a rabbit inhalation model to study M.tb. infection.
  • Quantified primary tubercle formation and bacillary load in infected rabbits.
  • Compared gross tubercle appearance and microscopic bacillary counts between strains.

Main Results:

  • Rabbits infected with CDC1551 and H37Rv produced a similar number of grossly visible primary tubercles.
  • Tubercles caused by the CDC1551 strain were smaller than those caused by H37Rv.
  • Fewer bacilli were recovered from CDC1551-induced tubercles compared to H37Rv-induced tubercles.

Conclusions:

  • The CDC1551 strain exhibits reduced virulence compared to the H37Rv strain in the rabbit model.
  • The observed epidemic caused by CDC1551 is likely attributed to enhanced transmissibility rather than increased virulence.

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