Comparison of selective and non-selective enrichment media in the detection of Listeria monocytogenes from meat containing Listeria innocua.
OBJECTIVE
This study investigated whether the higher incidence of recovery from meat of Listeria innocua compared with L. monocytogenes could be due to the laboratory media used, leading to an artificially lower detection of the pathogenic species, L. monocytogenes.


RESULTS
Minced beef was inoculated with L. monocytogenes, L. innocua, or a mixture of these species, and stored at 0 or 10 degrees C under vacuum or aerobic conditions for up to 28 days. Listeria were recovered from the minced beef using selective (University of Vermont Medium, UVM) and non-selective (Buffered Peptone Water, BPW) enrichment broths after 0, 14, and 28 days of storage. In general, there were no significant differences (P < 0.05) between the numbers of L. monocytogenes recovered from minced beef samples after 24 h enrichment in BPW and the numbers recovered using UVM. In addition, the presence of L. innocua in meat samples containing L. monocytogenes did not significantly (P < 0.05) affect the numbers of L. monocytogenes recovered using either enrichment broth. In most cases there were no significant differences (P < 0.05) between the numbers of L. innocua recovered from minced beef samples after 24 h enrichment in BPW compared with numbers recovered using UVM.


CONCLUSIONS
Listeria innocua was found to have no significant competitive advantage over L. monocytogenes in selective or non-selective enrichment media.


CONCLUSIONS
The results suggest that, in some instances, the use of a selective enrichment broth offers no advantage over a non-selective enrichment broth for the recovery of Listeria species from minced beef.
Duffy
G
G
The National Food Centre, Teagasc, Dublin, Ireland.
Walsh
D
D
Sheridan
J J
JJ
Logue
C M
CM
Harrington
D
D
Blair
I S
IS
McDowell
D A
DA
D015373:Bacterial Typing Techniques; D003470:Culture Media; D005516:Food Microbiology; D008087:Listeria / Q000254:growth & development*; D008089:Listeria monocytogenes / Q000302:isolation & purification*; D008460:Meat / Q000382:microbiology*
D003470:Culture Media