Potential Antibiotic Resurgence: Consecutive Silver Nanoparticle Applications Gradually Increase Bacterial...

The increasing prevalence of resistant bacteria has emerged as a critical public health concern due to their ability to resist multiple antibiotics. This study aimed to investigate whether repeated treatments with silver nanoparticles (AgNPs) could gradually decrease bacterial resistance to antibiotics. The methodology involved three consecutive applications of AgNPs on six bacterial strains, followed by assessing their susceptibility to 38 different antibiotics. To our knowledge, the following three phenomena were observed for the first time. (1) During three consecutive AgNP applications, it was revealed that all the studied bacteria gradually became more susceptible to 38 antibiotics; by the end of the treatments, susceptibility had doubled for five bacteria and tripled for Klebsiella pneumoniae compared to the susceptibility before the first AgNP application. (2) Three consecutive AgNP treatments led to 27-47% restoration of bacterial susceptibility to antibiotics, which had already completely lost their activity before the initial AgNP application. (3) Unlike previous studies, we discovered a novel effect: the repeated AgNP applications increased the susceptibility of Salmonella enteritidis and Staphylococcus aureus to AgNPs themselves. Obtained results suggest that AgNP treatments may offer a new promising strategy to combat antibiotic resistance.