Abstract
Listeria monocytogenes
is one of the most important emerging foodborne pathogens. The objectives of this work were to investigate the incidence of
Listeria
spp. and
L. monocytogenes
in soft cheese and ice cream in Assiut city, Egypt, and to examine the effect of some probiotic
Bifidobacterium
spp. (
Bifidobacterium breve
,
Bifidobacterium animalis
, or a mixture of the two) on the viability of
L. monocytogenes
in soft cheese. The existence of
Listeria
spp. and
L. monocytogenes
was examined in 30 samples of soft cheese and 30 samples of ice cream. Bacteriological analyses and molecular identification (using 16S rRNA gene and
hlyA
gene for
Listeria
spp. and
L. monocytogenes
, respectively) were performed on those samples. Additionally,
Bifidobacterium
spp. were incorporated in the making of soft cheese to study their inhibitory impacts on
L. monocytogenes
. Out of 60 samples of soft cheese and ice cream, 25 samples showed
Listeria
spp., while
L. monocytogenes
was found in only 2 soft cheese samples. Approximately 37% of soft cheese samples (11 out of 30) had
Listeria
spp. with about 18.0% (2 out of 11) exhibiting
L. monocytogenes
. In ice cream samples,
Listeria
spp. was presented by 47% (14 out of 30), while
L. monocytogenes
was not exhibited. Moreover, the addition of
B. animalis
to soft cheese in a concentration of 5% or combined with
B. breve
with a concentration of 2.5% for each resulted in decreasing
L. monocytogenes
efficiently during the ripening of soft cheese for 28 d.
Listeria
spp. is widely found in milk products. Probiotic bacteria, such as
Bifidobacterium
spp., can be utilized as a natural antimicrobial to preserve food and dairy products.