The objective of the research study was to determine the survival of Staphylococcus aureus ATCC 25923 strain in banana-milk drink fermented using Lactobacillus casei Łock 0900 strain, during its storage at a temperature of 15 ºC. Moreover, the effect was investigated of the addition of prebiotic (oligofructose), its concentration rate being 3 and 5 %, on the survival of the pathogen. An unfermented drink (neither probiotic nor prebiotic were added) was a control sample. Furthermore, the survival of S. aureus strain was determined in a product that contained no probiotic, but its pH value was similar to that of the probiotic drink after fermentation. It was found that the conditions in the fermented probiotic product were lethal for the S. aureus strain. During a 6 day period of analysis, the amount of living cells of the pathogen was reduced by 2 logarithmic orders. On the other hand, it was reported that the addition of oligofructose had no effect on the reduction in the living cells of that pathogen. In the unfermented product, during a 21-day period, the amount of S. aureus cells increased by 6 logarithmic orders. Regardless of the oligofructose concentration, a significant decrease was reported in the pH value of the product: from 5.02 (prior to fermentation) to 3.9 (on the last day of the analysis). The results of the control analysis show that the metabolites other than lactic acid have no impact on the dying of S. aureus strain.