Salmonella is a Gram-negative, facultative intracellular pathogen that is capable of causing gastroenteritis and typhoid fever in the affected host. Salmonella infections are reported as the second leading cause of foodborne illnesses in the United States. Salmonella has the potential to cause fatal bacterial infections in infants, the elderly and individuals with a suppressed immune system.
The
majority of foodborne Salmonella serovars can colonize in the
intestinal tracts of poultry. One of the major routes of human
salmonellosis is believed to be consumption and handling of contaminated
poultry and poultry products. According to surveillance data from the
U.S. Department of Agriculture's Food Safety and Inspection Service
(FSIS), Salmonella accounts for 23 percent of foodborne outbreaks and 31
percent of illness. Salmonella enterica serovar Enteritidis (S.
Enteritidis) is the most common serovar, causing 27 percent of
salmonellosis. The top of the list of the commodities to which S.
Enteritidis outbreaks were attributed was egg and laying hens.
If
Salmonella colonizes in the gut of laying hen heavily, a some eggs can
be contaminated with the bacterial cells. If even a few eggs used for
hatching are contaminated, then a limited number of chicks come out from
the egg with bacterial contamination (called vertical transfer), but
then it can be spread in millions of chicks within few days via
horizontal transfer.
The most common and
available current option for reducing established Salmonella
colonization in poultry flocks is the addition of antibiotics to poultry
feeds and water. However, due to the emergence of microorganisms
resistant to multiple classes of antibiotics, there are some concerns
that such practices may cause dissemination of antibiotic-resistant
human pathogens and increase untreatable human disease. In addition to
this, the cost of antibiotics puts increasing pressure on the search for
new ways to control colonization of Salmonella in the gut of laying
hens and stopping the vertical transfer of Salmonella to chicks and
eggs. Further antibiotic use is not allowed in organic/pasture poultry.
Recently,
it was found that the yolk of immunized chickens is a rich and
inexpensive source of polyclonal antibodies that decrease the attachment
of Salmonella onto chicken cells. Using specific bacterial antigen
antibodies provides protection against pathogens. When the feed of the
laying hens is supplemented with these antibodies, the newly hatched
chicks from these hens carry the antibodies from the mother via the egg.
Antibodies derived from the egg yolks of immunized hens have the added
benefit that large quantities of antibodies can be produced less
expensively than with mammalian sources. Further, the collection of eggs
is much less invasive and stressful to the animals as compared to using
a needle to obtain blood, and purification is also a relatively simple
process involving the removal of the lipoprotein fraction from the egg
yolk.
Polyclonal antibodies derived from egg
yolks have the potential for broader spectrum applications such as feed
supplements to control contamination of eggs with S. Enteritidis and
vertical transfer from eggs to chicks.
