VATIS UPDATE Article

Scientists from the Broad Institute of MIT and Harvard, the United States, have identified new genetic mutations that cause high-level antibiotic resistance. According to a 2013 report from the Centers for Disease Control and Prevention (CDCP), antibiotic-resistant infections kill at least 23,000 people in the United States annually. “Some species of bacteria, including mycobacteria, develop drug resistance as a result of mutations in their genes,” said Deborah Hung, at the Broad Institute.

Researchers grew hundreds of cultures of Mycobacterium smegmatis, related to the bacterium that causes tuberculosis. The bacteria was exposed to low antibiotic concentrations, where the drugs’ microbe-killing effects were slow. The team then monitored the killing of sensitive bacteria while isolating individual wells where mutants developed. The study showed that ribosomal mutations gave the bacteria resistance to many different classes of antibiotics that do not target ribosome.

The ribosomal mutations also increased resistance to heat shock and membrane stress. However, the reprogramming that occurred within the cells in response to the mutations made the bacteria much less sensitive to both antibiotic and non-antibiotic stresses. This suggests that, in species such as M. smegmatis, these types of mutations can enhance fitness in multidrug environments and serve as stepping stones toward the development of high-level drug resistance, despite the cost that the mutations have on growth.