Report: Bacteria become resistant to drugs when stressed

Bacteria become resistant to antibiotics when encountering stress such as high temperatures, according to a recent study.

Scientists from the University of California Irvine and Faculté de Médecine Denis Diderot in Paris found that when they put bacteria under stress, the bacteria spontaneously developed resistance to antibiotics. The researchers grew E. coli at high temperatures. It then grew resistance to rifampicin, BioMedCentral reports.

The mutations that were responsible for causing antibiotic resistance in the E. coli had different effects in other bacteria strains. The original test strain had a growth advantage at high temperature. Strains of bacteria with the same mutated subunit of RNA polymerase rpoB were still able to grow in the presence of rifampicin, but they did not have the same growth advantage as the high temperature strain.

"Our study shows that antibiotic resistance can occur even in the absence of antibiotics and that, depending on the type of bacteria, and growth conditions, rather than being costly to maintain can be highly beneficial," Olivier Tenaillon, the leader of the study, said, according to BioMedCentral. "Given that rifampicin is used to treat serious bacterial infections such as tuberculosis, leprosy, Legionnaire's disease, and for prophylaxis in cases of meningococcal meningitis, this development has important implications for public health."

The study demonstrated that the evolution of antibiotic resistance is governed by two separate properties of genes, pleiotropy and epistasis.

"Pleiotropy describes how the antibiotic resistance mutations affect other functions, hence their fate in other environments," Arjan de Visser, a scientist with the laboratory of genetics at Wageningen University in the Netherlands, said, according to BioMedCentral. "Epistasis describes how well different mutations combine in their effect on resistance, and therefore determines which mutational pathway will be preferred by evolution when several mutations are needed for full resistance."