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STUDIES ON THE OCCURRENCE OF BETA-LACTAMASES IN MEMBERS OF THE GENERA Salmonella AND Shigella ISOLATED FROM VARIOUS HOSPITALS

ABSTRACT

Salmonella and Shigella species isolated from human faecal samples were examined for Beta-lactamase production and resistance to some antibiotic agents. Age distribution of sources of resistant isolates showed that Shigella isolates from Youths (18 - 30 years) were more resistant to Ampicillin (66.67%) and Augmentin (33.33%) than isolates from Infants (6 months - 4 years) which showed percentage resistance of 3% to Ampicillin and 0% to Augmentin. Salmonella species isolated from Adults (31 – above) were more resistant to Augmentin (45%) and Ampicillin (40%), than isolates from Youths (18- 31 years) which showed percentage resistance of 40% to Ampicillin and 36.67% to Augmentin. Salmonella isolated from Infants (6 months – 4 years) showed p ercentage resistance of 28.57% to Ampicillin and 14.29% to Augmentin while isolates from Children (5 - 17 years) showed percentage resistance of 25% to Ampicillin and 12.5% to Augmentin. Sex distribution of sources of resistant isolates showed that Shigella species isolated from males were more resistant to Ampicillin (100%) while isolates from Females were more resistant to Augmentin (50%). Salmonella species isolated from Males showed high percentage resistance to Augmentin (60%) while isolates from Females were more resistant to Ampicillin (57.14%). Salmonella species showed higher percentage resistance to commonly used antibiotic agentsthan Shigellaspecies. The result showed that 8% of Shigella species and 21.5% of Salmonellaspecies were resistant to more than eight antibiotics with multiple antibioticresistance (MAR) index ranging from 0.2-0.9. Presumptive results of resistance curing treatments showed that the resistance traits were plasmid borne. Agarose gel electrophoresis (AGE) showed plasmids with molecular weights clustered around 23.1kb for species of Salmonella and Shigella. Conjugative transfer of resistance determinants was demonstratedfrom Salmonella to E. coli and from Salmonella to Shigella but not from Shigella to E. coli or to Salmonella. Studies on Beta-lactamase production showed that 9 (81.82%) of Shigella species and 22 (61.11%) of Salmonella species were Beta-lactamase producers with 3 (27.27%) of Shigella species and 20 (55.56%) of Salmonella species producing extended spectrum Beta-lactamases (ESBLs). ESBLs production is an acknowledge threat to modern medicine which is antibiotic based.

CHAPTER ONE

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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