In this work, the influence of various concentrations of modified nucleosides 2-fluoroarabinofuranosyl adenine, 2-amino-6-chloro-arabinofuranosyl purine and nucleotide 2-fluoroarabinofuranosyl adenine monophosphate on conditionally pathogenic bacterial cultures in the exponential phase of their growth, in which there is an intensive growth of cells that actively consume oxygen and nutrients, was evaluated. B. cereus cells belong to gram–positive, obligate aerobes, and P. Mirabilis to gram-negative, facultative anaerobes. It was found that gram-positive culture B. cereus is more susceptible to the action of the studied compounds: when the concentration of the studied compounds reaches 10‾3 M, a 30-40% slowdown in bacterial growth was found, while for P. mirabilis, 15-20% suppression of bacterial cell viability was noted at the same concentrations of compounds. It was also shown that the production of reactive oxygen species (ROS) in bacterial strains was enhanced in a dose-dependent manner when bacterial cells were cultured in the presence of all the compounds studied. The greatest increase in the level of ROS was found when bacterial cultures were cultured in the presence of fludarabine, which, however, does not completely correlate with the effect of inhibiting cell growth.