Left: Surface disinfection. Right: 1000fold increase of surviving cells as adaptation to repeated cycles of incomplete disinfection
Source: BAM, Division Biodeterioration and Reference Organisms
The increase of resistance against antimicrobials, such as antibiotics and disinfectants, is one of the big challenges of our time. Untreatable infections due to antibiotic resistance are already reality, causing globally hundreds of thousands of deaths per year. The emergence of resistance is fueled by the increasing use of antimicrobials. Bacteria constantly evolve (i.e., mutate) to adapt to their environment, and frequent exposure to antimicrobials favors bacteria with mutations that increase resistance to antimicrobials.
Disinfectants are biocides and are an important measure to control the transmission of bacterial (and viral) pathogens. The use of disinfectants has been surging over the last two years. But already before the SARS-CoV2 pandemic, the consumption in terms of mass of disinfectants was estimated to be higher than for antibiotics. Thus, it is likely that disinfectants are a driver of microbial adaptation to antimicrobials on a global scale. However, there are still many unknowns of how resistance to disinfectants develops and how this is related to resistance to antibiotics.
BAM researchers now published results in the scientific journal Nature Communications, in which they describe a novel principle for how bacteria adapt to stress imposed by the commonly used disinfectant and material preservative benzalkonium chloride (BAC). In the bacterium E. coli, they observed that a population, composed of billions of individual cells, contains a very small subpopulation, composed of thousands of cells, that can survive disinfection with BAC for much longer than most of the population. When the researchers treated the bacteria daily with the disinfectant, they found that the number of survivors increased a thousand times within only 4 days of repeated disinfection. By surviving disinfection, the subpopulation had enabled the whole population to adapt to the treatment. Eventually, the mutants displaced the susceptible ancestor bacteria. Furthermore, the evolved E. coli mutants showed changes in their susceptibility to antibiotics.
The findings of the study demonstrate how the (mis-)use of disinfectants can contribute to changes in susceptibilities of bacteria to disinfectants and antibiotics. Biocides are invaluable in many areas of today’s society. Just like antibiotics, they have saved countless lives and continue to do so. Safeguarding the efficacy of these precious resources is paramount and inappropriate use should be avoided.
Persistence against benzalkonium chloride promotes rapid evolution of tolerance during periodic disinfection
Nicolas Nordholt, Orestis Kanaris, Selina B.I. Schmidt, Frank Schreiber
published in Nature Communications, Vol. 12, issue 1, page 6792, 2021
BAM, Division Biodeterioration and Reference Organisms