Destruction of gram-negative food-borne pathogens by high pH involves disruption of the cytoplasmic membrane

A. F. Mendonca, T. L. Amoroso, Stephen John Knabel

Research output: Contribution to journalArticle

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Abstract

High pH has been shown to rapidly destroy gram-negative food-borne pathogens; however, the mechanism of destruction has not yet been elucidated. Escherichia coli O157:H7, Salmonella enteritidis ATCC 13706, and Listeria monocytogenes F5069 were suspended in NaHCO3-NaOH buffer solutions at pH 9, 10, 11, or 12 to give a final cell concentration of approximately 5.2 x 108 CFU/ml and then held at 37 or 45°C. At 0, 5, 10, and 15 min the suspensions were sterilely filtered and each filtrate was analyzed for material with A260. Viability of the cell suspensions was evaluated by enumeration on nonselective and selective agars. Cell morphology was evaluated by scanning electron microscopy and transmission electron microscopy. A260 increased dramatically with pH and temperature for both E. coli and S. enteritidis; however, with L. monocytogenes material with A260 was not detected at any of the pHs tested. At pH 12, numbers of E. coli and S. enteritidis decreased at least 8 logs within 15 s, whereas L. monocytogenes decreased by only 1 log in 10 min. There was a very strong correlation between the initial rate of release of material with A260 and death rate of the gram-negative pathogens (r = 0.997). At pH 12, gram-negative test cells appeared collapsed and showed evidence of lysis while gram-positive L. monocytogenes did not, when observed by scanning and transmission electron microscopy. It was concluded that destruction of gram-negative food-borne pathogens by high pH involves disruption of the cytoplasmic membrane.

Original languageEnglish (US)
Pages (from-to)4009-4014
Number of pages6
JournalApplied and environmental microbiology
Volume60
Issue number11
StatePublished - Jan 1 1994

Fingerprint

food pathogens
cell membranes
pathogen
Cell Membrane
Listeria monocytogenes
membrane
Food
Salmonella enteritidis
food
transmission electron microscopy
scanning electron microscopy
Salmonella Enteritidis
lysis
agar
Suspensions
viability
Escherichia coli
Scanning Transmission Electron Microscopy
Escherichia coli O157
Transmission Electron Microscopy

All Science Journal Classification (ASJC) codes

  • Biotechnology
  • Food Science
  • Applied Microbiology and Biotechnology
  • Ecology

Cite this

Mendonca, A. F. ; Amoroso, T. L. ; Knabel, Stephen John. / Destruction of gram-negative food-borne pathogens by high pH involves disruption of the cytoplasmic membrane. In: Applied and environmental microbiology. 1994 ; Vol. 60, No. 11. pp. 4009-4014.
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Destruction of gram-negative food-borne pathogens by high pH involves disruption of the cytoplasmic membrane. / Mendonca, A. F.; Amoroso, T. L.; Knabel, Stephen John.

In: Applied and environmental microbiology, Vol. 60, No. 11, 01.01.1994, p. 4009-4014.

Research output: Contribution to journalArticle

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