The effect of EDTA and trisodium phosphate, alone and in combination with nisin, on the growth of Arcobacter butzleri in culture

Arcobacter butzleri is a common contaminant of foods of animal origin and there is increasing evidence linking the organism to human illness. This study investigated the effectiveness of ethylene diamine tetra-acetic acid (EDTA) and trisodium phosphate (TSP) alone and in combination with nisin, on the growth of A. butzleri in culture. At 1 mM, 5 mM, 10 mM and 20 mM, EDTA inhibited growth, both alone and combined with 500 IU ml−1nisin, but only at 20 mM did the addition of nisin produce a statistically significant difference compared with EDTA alone (4·3 log10and 5·6 log10reduction respectively). Short-term simultaneous exposure with EDTA and 500 IU ml−1nisin was more effective than sequential treatment on both logarithmically growing and stationary phase cells. Growth of A. butzleri was inhibited by 0·5 mM TSP with simultaneous treatment being more effective than sequential treatment. After 10 min simultaneous treatment, only at 40 mM TSP (but not at lower concentrations) was there a statistically significant difference between TSP treatment alone and TSP plus 500 IU ml−1nisin (5·2 log10compared with 7·7 log10reduction). Thirty-minute treatment with 20 mM EDTA or 10 min with 10% TSP at 4°C, followed by incubation in the presence of 500 IU ml−1nisin, resulted in no viable cells being recovered after 24 h (>99·9% cell kill) indicating that a multiple hurdle approach is the most effective method of reducing growth and survival of A. butzleri in culture.