Enhanced inhibition of Escherichia coli O157:H7 by lysozyme and chelators.
This study examined the effects of three chelating agents (EDTA, disodium pyrophosphate [DSPP], and pentasodium tripolyphosphate [PSTPP]) on the inhibition of the growth of Escherichia coli O157:H7 by lysozyme. The objective of this study was to identify replacement chelators that exhibit synergistic properties similar to those of EDTA. The inhibitory effects of EDTA at 300 to 1,500 microg/ml and of DSPP and PSTPP at 3,000 to 15,000 microg/ml in combination with lysozyme at 200 to 600 microg/ml for up to 48 h at pHs of 6.0, 7.0, and 8.0 on four strains of E. coli O157:H7 was studied with the use of a microbroth dilution assay. The addition of EDTA enhanced lysozyme's inhibitory effect on strains of E. coli O157:H7. EDTA at > or = 300 microg/ml combined with lysozyme at 200 to 600 microg/ml was sufficient to inhibit the growth of the strains at pHs of 6.0 and 8.0. At pH 7.0, lysozyme at 200 to 600 microg/ml and EDTA concentrations of > or = 1,000 microg/ml were effective in inhibiting three of the four strains. DSPP at pH 6.0 was inhibitory at > or = 10,000 microg/ml when combined with lysozyme at 200 to 300 microg/ml. In contrast, PSTPP increased the inhibitory activity of lysozyme more effectively at pH 8.0. Lysozyme at 200 to 600 microg/ml was effective against two strains of E. coli O157:H7 when used in conjunction with PSTPP at > or = 5,000 microg/ml. The remaining strains were inhibited by PSTPP at > or = 10,000 microg/ml. Our results indicate that inhibition occurred with each lysozyme-chelator combination, but the concentrations of phosphates required to increase the antimicrobial spectrum of lysozyme against E. coli O157:H7 were higher than the EDTA concentrations required to achieve the same effect.
Boland
J S
JS
Department of Food Science and Technology, University of Tennessee, 2605 River Drive, Knoxville, Tennessee 37996-4500, USA.
Davidson
P M
PM
Weiss
J
J
D000890:Anti-Infective Agents / Q000494:pharmacology*; D002614:Chelating Agents / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D004357:Drug Synergism; D004492:Edetic Acid / Q000494:pharmacology; D019453:Escherichia coli O157 / Q000187:drug effects* / Q000254:growth & development; D005516:Food Microbiology; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008826:Microbial Sensitivity Tests; D009113:Muramidase / Q000494:pharmacology*
D000890:Anti-Infective Agents; D002614:Chelating Agents; D004492:Edetic Acid; D009113:Muramidase