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2. REVIEW OF LITERATURE

Poul¬try industry, intensive farming practice and irrational use of medicated feeds in broiler and layer operations to improve feed efficiency has made poultry as a major reservoir of antimicrobial resistant strains of Salmonella and E. coli (Crump et al., 2002)
Foodborne diseases and poisoning in the contemporary world are emerging and great public health concerns. Foodborne infections are widely spread in both developed and developing countries. (Akbar et al., 2011)
Poultry is an important farm species in almost all countries, it can be raised with limited cap¬ital and is an important cheap source of animal protein, Birds are intensively reared for meat and egg purpose. (Okorie-kanu et al., 2016)
Escherichia coli and serovars of S. enterica. dominant members of Enterobacteriaceae, are responsible for major cause of foodborne infections worldwide. (Helmy et al., 2017).

Aetiology, History and Background Escherichia coli
Escherichia coli is a gram-negative facultative bacteria belongs to the family Enterobacteriaceae. It is ubiquitous, commensal in animals, strains of E.coli food- and waterborne zoonotic infection (Dhama et al., 2013).
Pathogenic strains of E.coli associated with diarrhea are Enterotoxigenic E. coli (ETEC), Enteopathogenic E. coli (EPEC), Enterohemorrhagic E. coli (EHEC) or Shiga toxin-producing E. coli (STEC), Enteroinvasive E. coli (EIEC), Enteroaggregative E. coli (EAEC) and Diffusely adherent E. coli (DAEC). Enteropathogenic E. coli and certain Enterotoxigenic E. coli strains of E. coli, are significant are the main cause of global health burden of diarrheal disease (croxen et al., 2013).

Strains of E.coli are potential of causing either intestinal or extra-intestinal form of diseases. In humans strain of E. coli O157:H7 has been reported to be pathogenic causing hemorrhagic gastroenteritis and hemolytic uremic syndrome. In Poultry houses, rodent droppings, water, litter, fecal matter, and dust and feeds have been implicated as possible sources of E. coli. (Moawad et al., 2017).

Epidemiology
(Geidam et al 2012) reported the high prevalence of multidrug resistant E.coli over other microbial infection among poultry farms.
(Okorie-kanu et al., 2016) analyzed 68 composite samples of eggs obtained from farms and retail outlets in the study area, 37 (54.4%) were positive for pathogenic E. coli and reported that Eggs from farms recorded higher contamination with pathogenic E. coli than eggs obtained from retail outlets
Diagnosis of E.coli
Escherichia coli gram –ve rod-shaped organism belongs to Enterobacteriaceae family coliform group which ferments lactose and produces acid and gas. uidA gene which encodes for ?-D-glucuronidase is routinely used to specifically identify E. coli. ( Feng et al., 1991)
Probability of detecting target organisms of low concentrations enhanced by PCR which results in exponential amplification of specific DNA sequences and reduces the time required to obtain results. (Molina et al., 2015)

Salmonella
Salmonella enterica subtype Enteritidis major serotype of Salmonella responsible for food borne infection worldwide possess serious economic impact.
Salmonella is the common inhabitant in poultry harbours in gastrointestinal tract, reproductive organs, and birds will shed the organisms during defecation and egg laying. In poultry houses feces, litter, water acts as a source of infection to humans. (Frederick et al., 2011)
Salmonella Typhimurium, Salmonella Enteritidis serotypes of Salmonella spp. are reported to be pathogenic for both human and animal.
Diagnosis of Salmonella
PCR targeting invA gene for Salmonella is rapid, sensitive and specific for detection of Salmonella in many clinical samples. The invA gene encodes for protein membrane of bacteria, which is necessary for invasion to epithelial cells. (Lampel et al., 2000)
Salmonella detection by conventional methods are time consuming which includes selective enrichment and plating followed by biochemical characterization. Polymerase Chain
Reaction (PCR) found to be rapid and reliable method for detection Salmonella and other food borne pathogens (Rodulfo et al., 2012)
Epidemiology
(Davies et al 2003) carried out an investigation about distribution of Salmonella in layer breeding and egg production system and they found that Salmonella enterica serovar Enteritidis PT6 serovar established and infects the chicks.

ANTIBIOTIC SUSCEPTIBILITY OF ENTERIC BACTERIA IN POULTRY

Antimicrobial agents continuously fed to poultry as a antimicrobial growth promoters (AMGP) has resulted in emergence of resistant bacteria in poultry and accordinly their faecal ?ora also contains a relatively high proportion of resistant bacteria (Van den Bogaard et al., 1999)
Indiscriminate antibiotic usage is considered as the influencing factor results in selection, emergence and dissemination of antibiotic-resistant microorganisms, in both veterinary and human medicine. (Van den Bogaard et al., 2001)
(Mayrhofer et al., 2004) studied the Antimicrobial resistance profile of five major food-borne pathogens isolated from beef, pork and poultry and E.coli isolates stx1 positive strains obtained from poultry characterized phenotypically, exhibited a multiple drug resistance against tetracycline, kanamycin, sulfonamides, ampicillin and streptomycin antibiotics under disc diffusion method.
Salmonella and E. coli spp. resistance rates among food animals to antibiotics are reported to be high in most of countries (Mayrhofer et al., 2004)

Extended spectrum beta lactamases
Extended spectrum beta-lactamases (ESBLs) are enzymes commonly inhibited by inhibitors of Class A ?-lactamases such as clavulanic acid and others, such as sulbactam and tazobactam. Confers decreased susceptibility or resistance to Narrow spectrum and Expanded-spectrum cephalosporins, but do not affects cephamycin and carbapenem compounds. (Poirel et al., 2005)
Extended spectrum beta-lactamases (ESBL) incurring resistance to 3rd generation cephalosporins a specific type of antibiotic resistance contemporarily represents a major public health concern (Canton et al., 2008)

Most widely distributed enzymes of ESBL includes TEM and SHV with more than 160 and100 variants which has been recognised mostly associated with Enterobacteriaceae species,mainly K. pneumoniae and Enterobacter spp. isolates and recently with Pseudomonas aeruginosa and Acinetobacter baumannii. (Oliver et al., 2005)
CTX-M, ESBL enzyme confer resistance predominantly to cefotaxime rather than ceftazidime have been detected in many species (Canton et al., 2008).

Epidemiology
The spread of TEM and SHV plasmid-mediated enzymes dissemination provided a major impetus for the development of ‘?-lactamase-stable ?-lactams’. TEM-1,TEM-2 and SHV-1 types, broad-spectrum enzymes, categorized in group III, which are rapidly disseminating and became major sources of acquired resistance to the broad-spectrum penicillins (Livermore et al., 2008).
(Bortolaia et al., 2010) reported prevalence of 2 (3%) out of 60 cloacal swabs collected from were positive for CTX-M ESBL-producing E. coli in ?ocks of chicken egg layers reared in Danish organic systems
(Chauvin et al., 2013) reported that blaCTX-M-1 was along with blaCTX-M-15, are the most frequent ESBL genes harbored by E. coli in fecal samples
(Wasyl et al., 2013) reported that 42.3% of isolates from layers in Poland and other European countries, contained 3G Cephelosporin resistant E. coli which is significant and delineated that poultry and pigs might be a reservoir of third-generation cephalosporin-resistant E. coli.