Bacterial stress response to environmental radiation relating to the Fukushima radiation discharge event, Japan: Will environmental bacteria alter their antibiotic susceptibility profile?

Antibiotic resistance in clinical pathogens in humans may be traced back to resistance mechanisms in environmental bacteria and any factors, which are likely to alter (upregulate) resistance in environmental organisms, is of potential and eventual consequence to human pathogens. Furthermore, sublethal doses of gamma radiation to environmental organisms may cause sublethal stress and a selective pressure, which may lead to mutational events that alter the bacterium's susceptibility profile. A gamma (γ) radiation simulation experiment was performed to emulate the exposure of four environmental bacteria, including Listeria innocua, Bacillus subtilis, E. coli and Pseudomonas aeruginosa, to levels of radiation in and around Fukushima, Japan, equating to 1, 10 and 100 years equivalence exposure. Alteration to susceptibility to 14 antibiotics was measured as the primary endpoint. There was no significant alteration in the susceptibility of the Gram-positive organisms, whereas both Gram-negative organisms became slightly more susceptible to the antibiotics tested over time. These data indicate that such radiation exposure will not increase the antibiotic resistance profile of these organisms and hence not add to the global public health burden of increased antibiotic resistance in human bacterial pathogens.

► γ radiation contaminating the environment in and around the Fukushima nuclear plant, Japan, will not lead to an increase in antibiotic-resistance levels in Gram-positive bacteria, at 1, 10 or 100 years equivalence. ► γ radiation contaminating the environment in and around the Fukushima nuclear plant, Japan, may lead to a decrease in antibiotic-resistance levels in Gram-negative bacteria, at 1, 10 or 100 years equivalence.