project nazir naidkhai new

Download Project nazir naidkhai new

Post on 22-Jan-2018

162 views

Category:

Documents

1 download

Embed Size (px)

TRANSCRIPT

  • INTRODUCTION

    Salmonella has been long recognsized as an important pathogen of

    human, animals and poultry. The organism has its global distribution and

    usually causes enteric disease in human and animals through ingestion of

    contaminated food/feed mostly of origin (Sharma and Singh, 1997). Non-

    typhoidal salmonellosis is an important food borne infection with an estimated

    incidence of 1.3 billion cases and 3 million deaths all over the world (Thong et

    al., 1995).

    Enteric Salmonella infection is a global problem both in human beings

    and animals. Newborn and young animals commonly suffer from enteric

    infection within 15 days of their birth (Kaura et al., 2001). Enteric disorders

    that occur at organized animal farms in this country account for 10 to 30% of

    annual mortaility and thus are responsible for great economic losses. In human,

    diarrhoeal syndrome caused by non-typhoidal salmonella is common in tropical

    and developing countries. Available data on food poisoning indicate that

    poultry meat is frequently involved in cases of human salmonellosis (Galbraith,

    1990).

    Although, many of routine epidemiological features viz. host specificity,

    sources of infection, the forms of disease manifestation and carrier status of the

    organisms have been documented (Wray and Sojka, 1997; Thapliyal, 1979).

    Some new epidemiological parameters are being studied in recent years to

    elucidate the disease process of salmonellosis. Among these, antimicrogram

    1

  • studies and plasmid profile are of major importance. On study of

    epidemiological feature of salmoellosis, plasmids have been reported to play an

    important role in virulence and antibiotic resistance of Salmonella (Aarestrup

    et al., 1997).

    Bacteria are among the chief causal agents of acute diarrhoea and the

    majority of the bacterial enteropothogens appear to cause fluid lose by

    stimulation enterocytes to actively secrete electrolytes (Rao and Field, 1985).

    Elaboration of one or more enterotoxins is recognized as an important

    pathological attribute of some non-invasive diarrhoea including bacteria in

    elucidating of their enteropoathogenic activity (Rao and Field, 1985; Harne et

    al., 1994). Various Salmonella serotypes have been shown to produce

    enterotoxins (Baloda et al., 1983; Rahman et al 1991a). The enterotoxic moiety

    from salmonella serotypes has been purified and characterized by several

    workers (Finkalstein et al., 1987; Rahman et al., 1994). Salmonella

    pathogenesis is a complex and multifactorial phenomenon. Salmonella species

    interact with ileal mucosa and disrupt normal intestinal functions, which result

    in acute inflammatory cell influx, fluid secretion and enteritis (Wood et al.,

    1998). Many genes are required for full virulence but only a few of these have

    been shown to be necessary for the induction of enteritis (Wallis and Galyov,

    2000). Like many other gram-negative pathogenic bacteria, Salmonella

    possesses a dedicated protein secretion system denoted as Type III Secretion

    System (TTSS), which plays a central role in virulence (Huech, 1998).

    Salmonella serovars have been reported to produce several Type III secretions

    2

  • including SIP (Salmonella Invasion Protein) and Sop (Salmonella outer

    protein). Of the different Sop proteins, Sop B is associated with enteritis and

    diarrhoea. The gene encoding production of Salmonella outer protein (Sop B)

    is located on Salmonella specific DNA fragment representing a pathogenicity

    island, SPI 5 (Wood et al., 1998) and is found to be widely distributed among

    Salmonella (Rahman et al., 2001).

    Another important type III secretion is Sop E, which is associated with

    invasion by stimulating membrane ruffling (Hard et al., 1998). Unlike Sop B

    gene, the Sop E is not widely distributed among Salmonellae and diarrhoea and

    as the cases of this kind is frequently observed in livestock and poultry as well

    as in human.

    Apart from these outer proteins an important pathogenicity is exhibited

    by Salmonella species i.e. Salmonella enterotoxin. Although most of the

    Salmonella serovars were shown to produce enterotoxins, enterotoxigenicity of

    Salmonella has been found difficult to detect by different assays since

    Salmonella produce very level of enterotoxin when cultured by conventional

    methods (Baloda et al., 1983). Moreover, a major portion of Stn is retained as

    cell-bound content, which is not released in the extrcellular milieu (Kaura and

    Sharma, 1988). These are some Salmonella strains, which produce enterotoxin

    but do not release extracellularly and thus may escape different tests and

    detected to be non-enterotoxigenic if only entracellular occurrence of Stn is

    tested (Rahman et al., 1991a).

    3

  • Production of the enterotoxin (Stn) has been found to be mediated by the

    presence of Stn gene and it has been cloned and sequenced (Chary et al., 1993;

    Chopra et al., 1994). More recently, the Polymerase Chain Reaction (PCR) has

    been used for the detection of Stn gene (Prager et al., 1995; Rahman, 1999). Its

    detection by the PCR in field isolates of various Salmonella can indicate the

    protential of Stn production. Use of the standard PCR technique to study the

    presence of Stn gene among the field isolates can an important tool in the

    molecular characterization of field Salmonella isolates.

    The epidemiology and pathogenic process in salmonellosis is dictated

    by an array of factors that act in tandem and ultimately manifest into the typical

    symptoms of salmonellosis. In recent years, a number of virulence-associated

    fimbriae including Salmonella Enteritidis Fimbriae designated as SEF and

    Plasmid Encoded fimbriae designated as PEF have been identified and cloned

    (Clouthier et al., 1994). However, information on the occurrence of these

    fimbriae among the field isolates is still meagre (Rahman et al., 2000a). Both

    the above types of fimbriae are genetically encoded and its characterization can

    help in understanding the role of these genes in expression of these virulence

    factors.

    4

  • AIM AND OBJECTIVES

    The aim of the project was undertaken with the following objectives

    with given 50 samples:

    I. To study the Antimicrogram patterning of the given isolates.

    II. To study some of the molecular characteristics of the given

    isolates such as

    III. Detection of Sop B gene.

    IV. Detection of fimbrial genes (Sef and Pef).

    V. Detection of salmonella enterotoxin gene (Stn)

    VI. Detection of Sop E protein by Dot-ELISA.

    VII. Study on plasmid profiles.

    5

  • REVIEW OF LITERATURE

    Salmonella

    The importance of bacteria of the genus Salmonella as potential

    pathogens of human and animals needs no emphasis. Salmonella are widely

    distributed in nature. Currently, there are more than 2400 Salmonella serotypes

    prevalent in the world. A few of them are highly host specific, while majority

    of them are unadapted and can cause infection in a wide variety of animals

    species (Gupta and Verma, 1993). They are the chief cause of diarrhoeal

    disease all over the world (Gianella, 1980). Newborn and young animals

    commonly suffer from enteric infections within 15 days of their birth (Kaura et

    al., 2001). Enteric disorders that occur at organized animal farms account for

    10 to 30% of annual mortality in our country and are thus responsible for great

    economic loss Kaura et al., (2001).

    The genus name Salmonella has been adopted in the honor of Salmon,

    who isolated the hog cholera bacillus considered to be the causal agent of

    swine plague (Salmon and smith, 1885) but subsequently the organism was

    found to be only a secondary invader and named as Salmonella Choleraesuis.

    The typhoid bacillus was first seen by Eberth (1880) in the spleen and

    mesenteric gland of patient that died of typhoid and the organism was isolated

    by Gaffkey (1884) and Schotmuller (1901) differentiated Salmonella

    Paratyphi A and Salmonella Paratyphi B.

    6

  • The genus Salmonella of the Enterobacteriaceae family consists of

    Gram-negative bacilli, fermentative, aerobic or facultative anaerobic bacteria

    that are generally motile with peritichous flagella except Salmonella pullorum

    and Salmonella gallinarum. The organisms of the genus are non-lactose

    fermenters, oxidase negative, urease negative acetyl carbinol negative,

    potassium cyanide negative but citrate positive (Sleigh and Duguid, 1989).

    Nomenclature of Salmonella species

    Nomenclature and classification of Salmonella are ever changing. In

    recent years, the Kauffman- white Antigenic scheme as proposed by Ewing

    (1986) has been modified and updated and this updated version is being

    accepted by majority of the laboratories worldwide.The members of of the

    genus Salmonella have been grouped in two species, viz. Salmonella bongori

    containing 18 serovars and Salmonella enterica consisting of more than 2400

    serovars (Popoff