Growth of untreated and radiation-damaged Listeria as affected by environmental factors
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Updated: Oct 21, 2026

Measuring Bacterial Load and Immune Responses in Mice Infected with Listeria monocytogenes
Published on: August 9, 2011
J Farkas1, E Andrássy, L Mészáros
1Department of Refrigeration and Livestock-Products Technology, University of Horticulture and Food Industry, Budapest, Hungary.
Abstract:
The growth of untreated Listeria monocytogenes 4ab No. 10 and that of the surviving fraction of its population treated with 0.8 kGy gamma rays was investigated in a microtitreplate system at incubation temperatures between 3 degrees C and 35 degrees C in Tryptic Phosphate Broth (TPB) or Brain Heart Infusion Broth (BHIB) media containing NaCl between 0.25 to 16.75% (w/v), and acidified with citrate-phosphate buffers to pH values between 4.63 and 7.06. The initial viable count was 3 x 10(3)/ml. Time periods to visible growth were recorded. Radiation survivors showed increased salt- and pH-sensitivities and increased minimum temperature for growth in TPB-based media. Adverse effects of sub-optimal environmental factors (reduced water activity, pH and temperature) and radiation injury were much less pronounced in BHIB-based media. Polynomial equations describing the combined effects of hydrogen ion and salt concentrations on the detectable growth at 30 degrees C were constructed for quantitative assessment of interactions. The results demonstrate that combining environmental stresses with low-dose irradiation can control growth of L. monocytogenes.
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