Introduction And Literature Review
1.1 Introduction
In human medicine, the most important family of bacteria is Enterobacteriaceae, which includes genera and species that cause well-defined diseases, as well as nosocomial infections. The members of this family are Gram-negative, rod-shaped, non-spore-forming facultative anaerobes that ferment glucose and other sugars, reduce nitrate to nitrite, and produce catalase but seldom oxidase. Most Enterobacteriaceae are components of the gastrointestinal flora of humans and animals, although many are also widespread in the environment. Furthermore, these bacteria can cause many different infections, such as septicaemia, urinary tract infections, pneumonia, cholecystitis, cholangitis, peritonitis, wound infections, meningitis, and gastroenteritis, and they can give rise to sporadic infections or outbreaks (Donnenberg, 2009).
Salmonella and Shigella infections represent a major health problem worldwide, particularly indeveloping countries where they are recognized as the most frequent causes of morbidity and mortality (David and Frank, 2000, Mahbubur et al., 2007; Abdel et al., 2008). Life lost, together with the high costs to local public health care system, makes prevention and control a priority (Mahbubur et al., 2007; Yah et al., 2007a). The two pathogens have been associated with diarrhoea but the severity of the diarrhoea varies with the pathogens. GenerallyShigella causes bloody diarrhoea while Salmonella induces non-bloody gastroenteritis. Antibiotic resistantSalmonella and Shigella are of global concern because they affect both developed and developing countries due to increased international travel (David and Frank, 2000, Dubois et al., 2007).These concerns have been further reinforced in recent years by the emergence ofantimicrobial resistance among major groups of the enteric pathogens. The presence of antibiotic resistant bacteria from hospitalized patients throughout the world has been documented (Yah et al., 2007b).
Studies with Salmonella and Shigella are of particular relevance because these species can occupy multiple niches, including human and animal hosts (Martin et al., 1996, Levy, 1998; Khan, 2006). Reports have shown that the resistance of gastroenteric Salmonella and Shigella strains to antimicrobial agents is in large part due to the production of extended- spectrum β-lactamases (ESBLs) encoded on plasmids, as well as on the chromosome (David and Frank 2000).
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