The Beijing strain of TB

An article in the current Lancet discusses the Beijing genotype strain of TB and hypothesises that this more virulent, drug resistant and lethal form of TB evolved in response to the human immune system.

Reports from Africa indicate that the Beijing strain is surging ahead as

this strain had evolved unique properties that allowed for both acquisition and transmission of drug resistance

whilst a survey of MDR-TB in Europe found the Beijing strain to be present in a majority of cases. Another study from the Netherlands found that

Beijing genotype strains have a higher capacity to withstand tuberculosis treatment, even in the absence of drug resistance

The Beijing strain has the potential to challenge conventional TB diagnosis and treatment, which might be found to be both insufficient and inadequate.

Summary of the Lancet article below the fold

The Lancet Infectious Diseases, Volume 10, Issue 2, Pages 103 - 111, February 2010
doi:10.1016/S1473-3099(09)70330-5

Possible underlying mechanisms for successful emergence of the Mycobacterium tuberculosis Beijing genotype strains

Dr Ida Parwati MD a , Reinout van Crevel MD b, Dick van Soolingen PhD c

Summary

The wide geographic distribution of one clade of Mycobacterium tuberculosis, the Beijing genotype family, and its genetic homogeneity, suggests that strains belonging to this grouping might have a selective advantage over other M tuberculosis strains. This hypothesis was addressed by reviewing molecular-epidemiological, experimental, and clinical studies. Beijing strains represent about 50% of strains in east Asia and at least 13% of strains worldwide. Their emergence might be linked to escape from BCG vaccination, and to multidrug resistance, which is associated with the Beijing genotype in many areas. Different animal models have shown Beijing strains to be more virulent, and to cause more histopathological changes, higher outgrowth, and increased mortality. At a molecular level, Beijing strains have specific properties in terms of protein and lipid structures and their interaction with the human immune system. Finally, the Beijing genotype has been linked to polymorphisms in immune genes, suggesting the possibility of human—mycobacterial co-evolution. The emergence of the Beijing genotype family might represent an evolutionary response of M tuberculosis to vaccination or antibiotic treatment, with an important negative impact on tuberculosis control. More research is needed to further unravel the mechanisms underlying the emergence of M tuberculosis Beijing genotype strains, and examine the implications for future control strategies.