Factors affecting the susceptibility of Staphylococcus aureus CCRC 12657 to water soluble lactose chitosan derivative

In this study, the susceptibility of Staphylococcus aureus CCRC 12657 to water-soluble lactose chitosan derivative as influenced by pH, temperature and cell age were investigated. Besides, the effect of this chitosan derivative on enterotoxin production and cell leakage of S. aureus CCRC 12657 was also examined. It was found that the susceptibility of S. aureus CCRC 12657 to lactose chitosan derivative varied with incubation temperature, pH and cell age. The lactose chitosan derivative exerted a higher antibacterial activity against S. aureus CCRC 12657 at 37degreesC than at 22 and 5degreesC. At pH 6.5-7.0, S. aureus CCRC 12657 was more susceptible to the chitosan derivative than at pH 6.0 or 7.5. Besides, cells of S. aureus CCRC 12657 in the late-exponential phase (12 h) were most susceptible to the chitosan derivative followed by cells in the stationary phase (24 h) and mid-exponential phase (6 h). Supernatant of cell suspension showed a marked increase in absorbance at 280 nm after the cells of the test organism were exposed to deionized water-containing lactose chitosan derivative. Furthermore, it was also noted that the lactose chitosan derivative not only caused the death of S. aureus CCRC 12657 but also inhibited enterotoxin production in Brain-Heart infusion broth. (C) 2004 Elsevier Ltd. All rights reserved.