Effects of above-optimum growth temperature and cell morphology on thermotolerance of Listeria monocytogenes cells suspended in bovine milk

The thermotolerances of two different cell forms of Listeria monocytogenes (serotype 4b) grown at 37 and 42.8 degrees C in commercially pasteurized and laboratory-tyndallized whole milk (WM) were investigated. Test strains, after growth at 37 or 42.8 degreesC, were suspended in WM at concentrations...

Full description

Saved in:
Bibliographic Details
Published in:Applied and environmental microbiology 1998-06, Vol.64 (6), p.2065-2071
Main Authors: ROWAN, N. J, ANDERSON, J. G
Format: Article
Language:English
Subjects:
Action of physical and chemical agents on bacteria
Animals
Bacteriology
Biological and medical sciences
Cattle
Cells
Food industries
Food Microbiology
Fundamental and applied biological sciences. Psychology
Heat-Shock Proteins - biosynthesis
Hot Temperature
Listeria monocytogenes
Listeria monocytogenes - cytology
Listeria monocytogenes - growth & development
Listeria monocytogenes - pathogenicity
Microbiology
Milk
Milk - microbiology
Pasteurization
Sterilization
Temperature
Virulence
Citations: Items that this one cites
Items that cite this one
Online Access:Get full text
Tags: Add Tag
No Tags, Be the first to tag this record!
Description
Summary:The thermotolerances of two different cell forms of Listeria monocytogenes (serotype 4b) grown at 37 and 42.8 degrees C in commercially pasteurized and laboratory-tyndallized whole milk (WM) were investigated. Test strains, after growth at 37 or 42.8 degreesC, were suspended in WM at concentrations of approximately 1.5 x 10(8) to 3.0 x 10(8) cells/ml and were then heated at 56, 60, and 63 degrees C for various exposure times. Survival was determined by enumeration on tryptone-soya-yeast extract agar and Listeria selective agar, and D values (decimal reduction times) and Z values (numbers of degrees Celsius required to cause a 10-fold change in the D value) were calculated. Higher average recovery and higher D values (i.e., seen as a 2.5- to 3-fold increase in thermotolerance) were obtained when cells were grown at 42.8 degrees C prior to heat treatment. A relationship was observed between thermotolerance and cell morphology of L. monocytogenes. Atypical Listeria cell types (consisting predominantly of long cell chains measuring up to 60 micron in length) associated with rough (R) culture variants were shown to be 1.2-fold more thermotolerant than the typical dispersed cell form associated with normal smooth (S) cultures (P
ISSN:0099-2240
1098-5336
DOI:10.1128/aem.64.6.2065-2071.1998