Trisodium phosphate increases sensitivity of gram-negative bacteria to lysozyme and nisin.
Cell suspensions of Campylobacter jejuni, Escherichia coli, Pseudomonas fluorescens, and Salmonella enteritidis exposed to sublethal concentrations (0.5 to 5 mM) of trisodium phosphate (TSP) for 10 min showed greatly increased susceptibility to lysozyme (10 micrograms ml-1) and/or nisin (1 microM). Under optimal conditions at 37 degrees C, reductions in viable 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 cell kills (95%) were reduced by more than two log cycles. Cells dried on 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 microM) or lysozyme (100 micrograms 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 aureus by > 99.9%. The results suggest that the high TSP concentrations (approximately 10% wt/vol, 0.25 M) needed for successful decontamination of gram-negative bacteria, on the surface of poultry and other foodstuffs, may be substantially reduced by following TSP treatment with exposure to low lysozyme or nisin concentrations.
Carneiro de Melo
A M
AM
Division of Life Sciences, King's College London, UK.
Cassar
C A
CA
Miles
R J
RJ
D000818:Animals; D002645:Chickens / Q000382:microbiology; D005516:Food Microbiology; D006090:Gram-Negative Bacteria / Q000187:drug effects*; D009113:Muramidase / Q000494:pharmacology*; D009561:Nisin / Q000494:pharmacology*; D010710:Phosphates / Q000494:pharmacology*
D010710:Phosphates; D009561:Nisin; D009113:Muramidase; C018279:sodium phosphate