Sub-lethal damage of Listeria monocytogenes after long-term chilled storage at 4 degrees C.
The possibility that long term in vitro chilled storage may result in sub-lethal damage to Listeria monocytogenes cells was investigated by comparing growth of chill-stored (starvation at 4 degrees C) and fresh cultures on selective and non-selective media. Growth of freshly grown cells was minimally (3-8%) affected by selective LSAMM agar compared with non-selective Brain Heart Infusion agar. In contrast, numbers of chill-stored strains were reduced by greater than 99% after direct plating on the same selective and non-selective media. Furthermore, chill-stored strains were able to grow in standard selective broth (Listeria Selective broth and Fraser broth) only if undiluted inocula (approximately 10(5)-10(6) cfu ml-1) were used, whereas they were capable of growth in Brain Heart Infusion broth even when the lowest dilutions were used (approximately 10(1) cfu ml-1). The potential public health consequences of this finding for the isolation of Listeria monocytogenes from foods is considered.
Dykes
G A
GA
MIRINZ Food Technology & Research Ltd, Hamilton, New Zealand. g.dykes@mirinz.org.nz
Withers
K M
KM
D003080:Cold Temperature; D003470:Culture Media; D005511:Food Handling; D005516:Food Microbiology; D008089:Listeria monocytogenes / Q000254:growth & development*
D003470:Culture Media