Study Shows Resistance to Shorter Drug Regimens for Some Tuberculosis Strains Spreading Between Patients

A new study shows that “resistance to shorter and less toxic drug regimens for multidrug-resistant tuberculosis (MDR-TB) is emerging and spreading between patients.”

Analysis of Mycobacterium tuberculosis genomes from 27 countries “identified more than 500 strains of MDR-TB with additional resistance to at least one of the compounds in the BPaL/M (bedaquiline, pretomanid, and linezolid with or without moxifloxacin) regimen.” More than a quarter of those strains “appeared to have spread between patients.”

BPaL/M is a “6-month, all-oral drug regimen that is significantly shorter than the previous MDR-TB regimen, which lasted longer than 15 months and involved injectable drugs with severe and painful side effects. Randomized trial data has shown BPaL/M also has a much higher cure rate—90% or higher, compared with 50% and below for the previous regimen.”

The researchers analyzed the genomes of 6,926 M tuberculosis isolates collected over 13 years in Georgia, “a country with high MDR-TB burden.” Analysis of the 58 discovered strains found that 28% of them were “grouped in four genomic clusters in which all the strains had an identical mutational profile, indicating patient-to-patient transmission.” They then analyzed 81,576 genomes from 26 countries to determine if these highly drug-resistant TB strains were being transmitted elsewhere, and they identified “454 highly drug-resistant strains, and 117 of 420 (28%) were linked to direct transmission.”

Study author Galo Goig stated that “the fact that more than a quarter of these highly drug-resistant cases are due to patient-to-patient transmission, only two years after WHO endorsed the new regimen, is worrying.”