Study shows antimicrobial effective against listeria
in soft cheese
Source of Article: http://www.foodproductiondaily.com/Quality-Safety/Study-shows-antimicrobial-effective-against-listeria-in-soft-cheese
By Jane Byrne, 03-Dec-2008
Enterococcus faecium WHE 81, a
multi-bacteriocin producer, is effective as an
antimicrobial against Listeria monocytogenes
in Munster cheese,
a red smear soft cheese, according to a French study.
The authors of the
study, which was published in the journal Food Microbiology, said that
it is well established that soft cheese
is amongst the products that pose the highest risk with regard to human listeriosis.
The researchers said
that this present study, along with their previous research provides strong
evidence that, in case of smear soft cheese, bacteriocin-producing
lactic acid
bacteria can perform efficiently to control L. monocytogenes
when used as surface cultures.
Objective
The purpose of the
current research, according to the scientists involved, was to investigate
the antilisterial effectiveness of E. faecium WHE 81 used as culture for surface smear in Munster cheese.
E faecium WHE 81, isolated from
Munster
cheese has been reported to be a reputed multi-bacteriocin
producer with up to four independent antimicrobial
peptides produced, two of which are enterocins A
and B, which are known to be effective antilisterial
agents, claims the report.
Results
The researchers said
that, during the ripening period, L. monocytogenes
rapidly initiated growth in control samples, with counts of approximately 104
CFU g−1 on day 17 and of approximately 105 CFU g−1 on day 21.
Conversely, in the
test samples limited increases or no increase at all in L. monocytogenes counts was recorded during the cheese
ripening. At the term of the ripening period, L. monocytogenes
often remained below enumeration levels and most of the samples analyzed were
free from the pathogen, claims the study.
And, according to the
published findings, the inoculation of the cheese with E. faecium WHE 81 did not result in any perceivable
change in pH, fungal flora or pigmented bacteria in the cheese rind during
ripening.
“In our experiments,
L. monocytogenes could not initiate growth and was
even eradicated in most cheeses analyzed.
“Therefore, the
supplementary use of bacteriocin-producing E. faecium appears to be a promising measure to combat L. monocytogenes in an infected production line,” claim the researchers.
Mutli-bacteriocin approach
However, the
scientists note that the continuous use of a bacteriocin
is questionable as a primary means of food preservation as resistant Listeria
mutants often occur as a result.
“In this regard, the
fact that E. faecium WHE 81 could produce several bacteriocins with different structures is an interesting
feature, especially since synergistic activity has been shown between enterocin A and enterocin B,
two of the bacteriocins produced by this
strain," claim the research team.
They argue, therefore,
that the use of E. faecium WHE 81 as an
antimicrobial could be considered as a mutli-bacteriocin
hurdle approach, likely to be more efficient in preventing the growth of
undesired bacteria than the use of a single bacteriocin
producer.
Source: Food
Microbiology Volume 26 Issue 1 February 2009, Pages 16-20
Published online ahead of print
Title: Smearing of soft cheese with Enterococcus
faecium WHE 81, a multi-bacteriocin
producer, against Listeria monocytogenes
Authors: E. Izquierdo, E. Marchioni,
D. Aoude-Werner, C. Hasselmann,
S. Ennahar
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