Vidyya Medical News Service
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Volume 6 Issue 59 Published - 14:00 UTC 08:00 EST 28-Feb-2004 Next Update - 14:00 UTC 08:00 EST 29-Feb-2004
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Does tuberculosis result from one strain, or more?

South African investigators have challenged the premise that tuberculosis generally results from a single strain of Mycobacterium tuberculosis by demonstrating that multiple infections are present in patients with active tuberculosis.

The setting for their research was a site with a high infection rate. The researchers analyzed pre-treatment sputum specimens from 200 patients over age 15. All had been diagnosed with smear-positive TB.

The authors demonstrated that 19 percent of the patients in the study were simultaneously infected with strains belonging to the Beijing and non-Beijing evolutionary lineages. The researchers said that the occurrence of multiple infections took place in 17 percent of the new tuberculosis cases.

The authors also noted that from data in the study, which was collected at an epidemiologic field site in Cape Town from March 2000 to June 2002, it was not possible to predict the order in which the different infections occurred. They pointed out that reinfection might reactivate a latent infection which, in turn, might be responsible for disease progression. They said that if this scenario were true, such cases would present strains that are different from their source cases even though contact existed.

The study appears in the first issue for March 2004 of the American Thoracic Society's peer-reviewed American Journal of Respiratory and Critical Care Medicine.



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