The response of Staphylococcus aureus germ to the action of ionizing radiation and cold plasma jet was studied in the frame of a comparative experimental research. The inactivation effect of electromagnetic ionizing radiations provided by medical X-ray device has resulted in up to 75% diminution of bacterial cell density, while for the same radiation doses provided by 6 MeV electron beam delivered by hospital radiotherapy accelerator, three times slighter effect has resulted. It was further shown that bacteria inactivation could be obtained by applying cold plasma treatment for shortened irradiation times; 100 s instead of 50 min having similar effect of about 73% efficiency on S. aureus, as resulted from counting the survival colony forming units. The S. aureus antimicrobial susceptibility was found slightly changed for X-rays but not for electron beam irradiation or cold plasma exposure.