Salmonella is a Gram-negative emerging zoonotic food pathogen having
worldwide distribution.
Salmonella enterica is one of the most commonly detected
enteric foodborne pathogen in humans and animals.
This bacterial species consist of more than 2,500 serovars which are widely
dispersed in insects, reptiles, birds and mammals including humans (Baumler
et al., 1998).
Prevalence of these serotypes may vary considerably between localities,
districts, regions and countries (OIE, 2010).
Most human infection are caused by non-host specific Salmonella serovars like S.
Typhimurium and S. Enteritidis (Hendriksen et al.,
2011; Dar et al., 2017). Non-typhoidal
Salmonella (NTS) species are commonly
encountered in most of the foodborne outbreaks worldwide. Salmonellosis caused by
these zoonotically important serovars are not restricted to humans alone, and
are capable of producing gastrointestinal illness to systemic infection in both
humans and animals (Andino and Hanning, 2015).
In most of the cases the disease can be self-limiting in healthy individual. Salmonellosis
has been reported in most of the countries, high incidence of NTS infection is reported
in areas of intensive animal husbandry.
This is the reason for high intensity of foodborne salmonellosis cases
in USA and E.U (Antunes et al., 2015).

            The global impact of foodborne
salmonellosis is very high, since it is causing 93.8 million human infections
and 155,000 deaths annually (Majowicz et al., 2010; Scallan et al., 2012). Poultry and foods
of animal origin are the major sources of human non-typhoidal salmonellosis (de Freitas- Neto et al., 2010). Humans usually
get infection by ingesting of contaminated food or by direct contact of
infected animal. Poultry are the major reservoir of human associated Salmonella species, including the multi
drug resistant strains of Salmonella (Abulreesh, 2012). Birds
carry the bacterium in their gut without showing any symptoms and shed the
organism through their feces (Adzitey et al., 2011), making it
difficult to diagnose the infection. Salmonella
is transmitted in poultry either by vertical transmission or from the
environmental sources. Sub-clinically
infected birds can spread the organism easily within the flock and increase the
zoonotic transmission risk. Entry of pathogen to flock not only
affect the production system but also results in socioeconomic and health
consequences to whole society.

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            Progressive incidence of zoonotic
foodborne Salmonellosis has increased during the last two decades,this has been
related to increased consumption of poultry meat,egg
and meat products over the last the few decades (Rocourtet al., 2003; Foley et al., 2011;Park et al.,
2013). The Centers for Disease
Control and Prevention (CDC) is regularly monitoring the human salmonellosis
associated with poultry and poultry products (CDC, 2010). The over use of antibiotic in poultry industry led to emergence
of multidrug-resistant strains of non-typhoidal Salmonella species, it may cause serious infections as they spread
within the food chain. In this situation presence
of Salmonella in poultry will
increase pressure on producing countries to introduce targets for reducing
levels of infection by specific monitoring and
control measures.

    
       Salmonellosis remains a major socio economic burden
in developing countries with low
health care settings, unhygienic production and processing area of foods (Baird-parker, 1990). Since
poultry is a vehicle for Salmonella infection, pathogen control strategy at
pre-harvest environments is the first step in reducing the presence of
foodborne pathogens in poultry eggs and meat. Besides using usual preventive
measures like disinfection, control of Salmonella
carriers, UV irradiation etc, application of immune based strategies at farm level
could be made significantly more effective to control Salmonella infection (Dar et al., 2017). As a part of
immunization strategies several studies have been conducted to identify a good immunogen
from Salmonella. More importantly
these studies identified the antigenic nature of outer membraneprotein of Salmonella species (Nandakumar et al., 1993; Kumar et al., 2009; Jhaet al., 2012).These
investigations also have led to the characterization and evaluation of diagnostic
potential of outer membrane protein because of its surface exposed antigen (Devananda, 1911). Such challenging findings opened a new window
to surveillance and diagnosis of Salmonella
infection

            The high incidence of poultry associated
human salmonellosis requisites the rapid, sophisticated diagnostic tools for studying pathogens, including
genomics and proteomics in diagnostic study. Several methods have been
developed for detecting Salmonella
from poultry including culture techniques (FDA, 1992),
DNA based techniques, inmmunoassays etc. Generally
diagnostic methods like conventional culture methods, detection of DNA by PCR
are being commonly employed for identification of organism, but it does not
indicate the presence of live bacteria (Barrow, 2012),
whereas the conventional culture methods are time consuming and
laborious.Serologic test like agglutination
test, ELISA, radioimmunoassay, fluorescent immunoassay etc can diagnose and
identify the prevailing condition for a
detailed epidemiological investigation. ELISA is a sensitive serological tool
widely used in different research areas because of its potential for
immunological detection (Voller et al., 1976). ELISA is not only gives the information
about the infection status of the flock but also differentiate the recently
infected from convalescent one (El -Fakar and Rabie, 2009). A limited number of
antigens have been tested in ELISA for diagnosis of salmonellosis in poultry.
Antigen such as flagellar antigen (fliC and fljB) (Minicozzi et al., 2013), outer membrane
protein (OmpC) (Manoj et al., 2015) have been extensively used in ELISA. Antibody responses to Salmonella outer membrane antigen are positively correlatedwith the
Salmonella burden in the flock. Thus,
serological tests may increase thedegree of detection of birds infected with Salmonella.

 

            Recently outer membrane protein
OmpC of Salmonella Typhimurium have
received a lot of attention for its capability in diagnostic assay (Manoj, 2012) and as a vaccine
candidate (Prejit et al., 2013). However only little information is
available about OmpF protein of Salmonella
Typhimurium. Thus this OmpF protein is being evaluated
for the first time as a diagnostic antigen.The present study relates to improved diagnostic tools for
veterinary use for serodiagnosis of salmonellosis in poultry by developing
recombinant OmpF protein.