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Beijing strain of TB not associated with drug resistance
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Beijing strains of Mycobacterium tuberculosis did not appear associated with drug resistance, but they were significantly associated with genotypic clustering, researchers from Fudan University in China suggest.
“There are many different strains of M. tuberculosis, but the Beijing family genotype is widespread and is a major concern,” the researchers wrote. “Researchers have hypothesized that Beijing strains have unique properties that might explain their widespread distribution, such as an escape from the protective effect of the [bacille Calmette-Guérin] vaccine, efficient dissemination or increased virulence, rapid and increased expansion in younger populations and an increased risk of drug resistance.”
The researchers conducted a population-based molecular epidemiologic study to determine whether the Beijing strains were more likely to spread or become drug resistant. They analyzed specimens from 1,448 patients with confirmed TB in China from 2009 to 2010.
Using genotyping, they found that 75% of the TB strains were the Beijing strains. They grouped the strains into 145 clusters, and the largest cluster was formed by a Beijing strain. The proportion of clustered strains was higher for Beijing strains. When they analyzed the patient characteristics, they found that younger patients were more likely to be infected with a Beijing strain.
As for drug resistance, they found that Beijing strains were not associated with drug resistance any more than non-Beijing strains. The researchers also identified six sublineages of the Beijing strains in this patient population.
“Our findings confirm that the Beijing strains are not homogeneous; there are identifiable sublineages of Beijing strains,” the researchers wrote. “Future studies of Beijing family strains should avoid assuming and attributing characteristics to the entire family, and should assess the strains of specific sublineages and/or settings.”
Disclosure: The researchers report no relevant financial disclosures.
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