Biomedical Engineering Reference
In-Depth Information
2.4
Bacteriophages
Bacteriophages are obligate parasites of bacteria. Lytic bacteriophages offer a
great potential as natural biopreservative agents, due to their capacity to selec-
tively control bacterial populations. This phenomenon occurs spontaneously in
Nature, but can also be applied purposedly in food systems. One feature of bac-
teriophages is their high host specifi city, at the level of species and even strains.
Specifi city at strain level can be a limitation for application of bacteriophages.
Nevertheless, several studies have shown the effi cacy in food systems of mixtures
containing different bacteriophages and also broad-host range bacteriophages
that were able to attack a high number of bacterial strains, including the most
virulent strains found in foods (Hagens and Loessner
2007
,
2010
,
2014
; Sharma
2013
; Sulakvelidze
2013
). Control of
L. monocytogenes
by bacteriophages has
been addressed in many different ready-to-eat foods of animal as well as plant
origin. Commercial phage preparations like ListShield™ (containing a mixture
of six naturally occurring listeriophages) and Listex™ P100 (based on listerio-
phage P100) have been approved by the FDA and USDA (Hagens and Loessner
2014
). Bacteriophages specifi c for
Salmonella
serotypes have also been used on
various food substrates such as sprouted seeds and animal skins and carcasses.
The commercial preparation SalmoFresh contains a cocktail of naturally occur-
ring lytic bacteriophages that selectively and specifi cally kill
Salmonella
, includ-
ing strains belonging to the most common/highly pathogenic serotypes:
Typhimurium, Enteritidis, Heidelberg, Newport, Hadar, Kentucky, and Thompson.
Bacteriophages specifi c for
E. coli
(including virulent strains) have also shown
effi cacy on different food substrates. The commercial preparation EcoShield™
contains a cocktail of three lytic phages specifi c for
E. coli
O157:H7. Illustrative
studies on application of bacteriophages can be found in the scientifi c literature
for other human pathogenic or toxinogenic bacteria such as
Shigella
spp. (Zhang
et al.
2013
),
C. jejuni
(Bigwood et al.
2008
),
Cronobacter sakazakii
(Zuber et al.
2008
),
S. aureus
(Bueno et al.
2012
), as well as spoilage bacteria such as
Pseudomonas fl uorescens
(Sillankorva et al.
2008
).
Brochothrix thermosphacta
(Greer and Dilts
2002
) or
Leuconostoc gelidum
(Greer et al.
2007
).
Another emerging fi eld of interest is the application of bacteriophages for reduc-
ing the carriage of zoonotic agents in livestock and poultry and also for the prophil-
axy and therapy in diseased animals. Phage therapy is potentially useful in virulent
Salmonella
and
E. coli
infections in chickens, calves and pigs, and in control of the
food-borne pathogens
Salmonella
and
C. jejuni
in chickens and
E. coli
O157:H7 in
cattle (Johnson et al.
2008
; Connerton et al.
2011
; Sulakvelidze
2013
; Endersen
et al.
2014
). Selective application of bacteriophages could improve animal health
and animal production and reduce the risks of transmission of zoonotic agents to
humans.
