Amsc. Demelo et al., TRISODIUM PHOSPHATE INCREASES SENSITIVITY OF GRAM-NEGATIVE BACTERIA TO LYSOZYME AND NISIN, Journal of food protection, 61(7), 1998, pp. 839-843
Cell suspensions of Campylobacter jejuni, Escherichia coli, Pseudomona
s fluorescens, and Salmonella enteritidis exposed to sublethal concent
rations (0.5 to 5 mM) of trisodium phosphate (TSP) for 10 min showed g
reatly increased susceptibility to lysozyme (10 mu g ml(-1)) and/or ni
sin (1 mu M) Under optimal conditions at 37 degrees C, reductions in v
iable count after 30 min were up to six log cycles. At 4 degrees C, C.
jejuni showed greater resistance than at 37 degrees C, and maximal ce
ll kills (95%) were reduced by more than two log cycles. Cells dried o
n the surface of chicken skin were more resistant than suspended cells
to TSP-lysozyme and TSP-nisin treatments; nevertheless, at 37 degrees
C, kills varied from approximately 95% for S. enteritidis cells with
nisin (30 mu M) or lysozyme (100 mu g ml(-1)) to >99.9% for C. jejuni
and E. coli cells with nisin. Under the experimental conditions used,
nisin also reduced viable counts of skin-attached Staphylococcus aureu
s by >99.9%. The results suggest that the high TSP concentrations (app
roximately 10% wt/vol, 0.25 M) needed for successful decontamination o
f gram-negative bacteria, on the surface of poultry and other foodstuf
fs, may be substantially reduced by following TSP treatment with expos
ure to low lysozyme or nisin concentrations.