3 research outputs found
Quantifying the combined effect of salt and temperature on the growth of <i>Listeria</i> strains isolated from salmon and salmon processing environments
The effects of temperature and salt concentration on the growth of relevant strains of L. monocytogenes and Listeria innocua, were quantified based on growth in a liquid broth medium, monitored by measuring turbidity. Absorbance curves were used to estimate maximum growth rate and lag time. The growth rates increase with increasing temperatures. The levels were quite similar for both species, although L. monocytogenes showed higher growth rate than L. innocua at 4 °C. Lag time was more affected both by temperature and salt concentration, and these effects were most prominent for L. innocua.</i
An interlaboratory study to find an alternative to the MPN technique for enumerating Escherichia coli in shellfish
8 páginas, 4 tablas, 3 figuras.-- I. D. Ogden ... et al.Nine laboratories in eight countries tested 16 batches of common mussels (Mytilus edulis) over a 32 week period in order
to find an alternative to the Most Probable Number (MPN) technique to enumerate E. coli. The alternatives investigated
included the 3M Petrifilm system, the Merck Chromocult agar method and a Malthus conductance technique. The Petrifilm
was found to be unsuitable and was subsequently dropped from the trial. After 669 analyses, a correlation of 0.83 was
observed for log E. coli counts between the MPN and Chromocult methods and there was no significant evidence that either
method tended to give higher readings than the other. The MPN was slightly better than the Chromocult method for
repeatability but the Chromocult was slightly better for reproducibility. However, the observed differences are probably too
small to be of practical importance. On the basis of these data therefore, the two methods appear equally suitable for E. coli
enumeration in shellfish. There were poor correlations between these methods and the Malthus technique. A small but
significant number of samples tested positive on the Malthus instrument but were recorded negative on the MPN and
Chromocult tests. Subsequent analysis positively identified E. coli from these Malthus assays. After statistical analysis,
errors were noted in both the MPN and Chromocult methods but it was found that there would be no statistical differences if
the Chromocult agar were used as an alternative to the MPN techniqueEuropean Commission DGXIV (Fisheries)Peer reviewe