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.
Division of Life Sciences, King's College London, UK.
A M
AM
Carneiro de Melo
C A
CA
Cassar
R J
RJ
Miles
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