Impact of drug resistance on fitness of Mycobacterium tuberculosis strains of the W-Beijing genotype

Abstract

Mycobacterium tuberculosis strains of the W-Beijing genotype became a common cause of tuberculosis during the past years and they are often associated with drug resistance. The biological factors facilitating the selection and wide dissemination of these strains are not known. To determine how acquisition of drug resistance affected growth of strains of the W-Beijing genotype, the growth of 55 M. tuberculosis isolates were studied using the BBL MGIT Mycobacteria Growth Indicator Tube and the BACTEC MGIT 960 System. Susceptible strains of non-Beijing genotypes were found to be the most fit strains. Drug-resistant strains of non-Beijing genotypes were more likely to grow slower than susceptible strains (P=0.001). Drug-resistant strains of the W-Beijing genotype had two tendencies of growth: some of them showed reduced growth compared to susceptible strains, while others did not show loss of fitness measured as growth.

Epidemic Spread of Multidrug-Resistant Tuberculosis in Johannesburg, South Africa

“…Its ability to replace resident strains was demonstrated in a community-based study in Cape Town that prospectively tracked the rapid emergence of Beijing genotype strains over a 12-year period (44). The success and global spread of the Beijing genotype has been ascribed to multiple factors (45), including resistance to Mycobacterium bovis BCG-induced immunity (46), potential hypervirulence, and reduced fitness costs associated with the acquisition of drug resistance (47). The resolution of Beijing genotype strains was enhanced by 24-MIRU typing relative to the 12-MIRU typing.…”

Beijing and Haarlem Genotypes Are Overrepresented among Children with Drug-Resistant Tuberculosis in the Western Cape Province of South Africa

“…The geographic variability observed in this association (30), the frequent clustering of resistant genotypes, and their successful spread within the Russian prison system (7,29) suggest recent clonal expansion. This is supported by evidence that some strains of the Beijing genotype family retain fitness despite the acquisition of drug resistance (28). The Haarlem genotype family has also been associated with drug resistance and rapid clonal expansion (8,19).…”

Evolution and Transmission Patterns of Extensively Drug-Resistant Tuberculosis in China

“…A recent report in the Western Cape of South Africa showed that although MDR-TB was spreading by transmission, XDR-TB appeared to be acquired but not clonally derived (8). The diversity of the resistance mutations in Beijing strains has also been observed in Russia (9) and Japan (10), indicating independent acquisition. This is in contrast to the highly publicized outbreak of XDR-TB in HIV-positive individuals due to transmission in Tugela Ferry, South Africa.…”