The influence of the sodium chloride concentration in the growth medium of Staphylococcus aureus on its attachment to lettuce surfaces

摘要

In this study, we aimed to investigate the effects of bacterial growth conditions, such as NaCl concentration, on the level of attachment of Staphylococcus aureus to fresh food. Lettuce coupons were exposed to S. aureus, that had been grown in different NaCl concentrations, in suspension for 24 h at 5 °C (non-growth conditions). By measuring the number of bacteria remaining in the suspensions, we calculated the number attached to the lettuce leaves. The surface hydrophobicity, heat tolerance, and zeta potential of S. aureus grown under different NaCl concentrations were also measured. We found that the attachment of S. aureus to food was influenced by the NaCl concentration in the growth medium. Although the attachment level decreased due to the addition of NaCl, a marked increase occurred when S. aureus was grown in 8% NaCl. The minimum values for surface hydrophobicity, heat tolerance, and zeta potential also occurred at a concentration of 8% NaCl. However, this pattern was not observed with changes in the concentration of KC1. These results will be relevant to the study of hazardous biofilms on fresh foods and food processing equipment, as well as quality assurance procedures and food safety.