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Isolation, identification, and selection of lactic acid bacteria
from alfalfa sprouts for competitive inhibition of foodborne pathogens
May 2004
Journal of Food Protection Vol. 67, No. 5
Wilderdyke M.R.[1]; Smith D.A.[1]; Brashears M.M.[2]
[1] Department of Food Science and Technology, University of Nebraska, Lincoln,
Nebraska 68583-0919, USA [2] Department of Animal Science and Food Technology,
Texas Tech University, Lubbock, Texas 79409-2141, USA
Abstract:
Several studies have investigated the control of pathogens on alfalfa sprouts,
and some treatments have been shown to be effective in reducing pathogen
populations. However, control methods investigated thus far only provide
pathogen control at a given point in the sprouting process and can affect
germination. Competitive inhibition of pathogens with lactic acid bacteria might
provide pathogen control throughout the sprouting process and up to consumption.
The purpose of this study was to isolate and identify lactic acid bacteria from
alfalfa sprouts to inhibit the growth of foodborne pathogens. Fifty-eight lactic
acid bacteria isolates were obtained from alfalfa seeds and sprouts. These
isolates were evaluated for inhibitory action against Salmonella enterica,
Escherichia coli O157:H7, and Listeria monocytogenes by agar spot tests. All
pathogens were inhibited by 32 (55%) of the isolates, S. enterica by 56 (97%),
E. coli O157:H7 by 49 (84%), and L. monocytogenes by 41 (71%). The isolates were
identified by the Analytical Profile Index evaluation of carbohydrate
utilization. Isolates obtained from a sample of alfalfa seeds and identified as
Lactococcus lactis subsp. lactis showed zones of inhibition of 4.0 mm or greater
for all pathogens. One of these isolates, Lactococcus lactis subsp. lactis (L7),
and an isolate previously obtained, Pediococcus acidilactici (D3), were
evaluated for competitive inhibition of S. enterica, E. coli O157:H7, and L.
monocytogenes in deMan Rogosa Sharpe agar and broth. Pathogen populations were
significantly reduced by day 5. The selected isolates will be further evaluated
in future studies for inhibitory action toward S. enterica, E. coli O157:H7, and
L. monocytogenes during sprouting.
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