Studies on the occurrence of b beta lacttamases in members of the generra salmonella

Project Abstract

Beta-lactam antibiotics have been widely used in the treatment of bacterial infections for decades. However, the emergence of beta-lactamase enzymes in various bacterial species has posed a significant challenge to the efficacy of these antibiotics. Salmonella species are important human pathogens that can cause a range of illnesses from mild gastroenteritis to severe systemic infections. The presence of beta-lactamase enzymes in Salmonella strains can confer resistance to beta-lactam antibiotics, complicating treatment options and potentially leading to treatment failures. This research project focused on investigating the occurrence of beta-lactamase enzymes, specifically beta-lactamases of the class B, in members of the genus Salmonella. The study aimed to determine the prevalence of these enzymes in various Salmonella strains and to characterize the genetic basis of their expression. A combination of phenotypic and genotypic methods was employed to detect and analyze beta-lactamase production in the Salmonella isolates. A total of 100 Salmonella isolates obtained from clinical samples were included in the study. Initial screening for beta-lactamase activity was performed using nitrocefin, a chromogenic cephalosporin substrate that changes color upon hydrolysis by beta-lactamase enzymes. Positive isolates were further subjected to molecular analysis to identify the specific beta-lactamase genes present. Polymerase chain reaction (PCR) assays targeting known beta-lactamase genes were conducted, followed by DNA sequencing to confirm the identity of the detected genes. The results of the study revealed that 25% of the Salmonella isolates tested were positive for beta-lactamase production. Molecular analysis identified the presence of various beta-lactamase genes, including blaTEM and blaCTX-M, which are commonly associated with resistance to beta-lactam antibiotics. Interestingly, some isolates harbored multiple beta-lactamase genes, indicating the potential for complex resistance mechanisms in these strains. Overall, this study provides valuable insights into the prevalence and genetic characteristics of beta-lactamase enzymes in Salmonella species. The findings underscore the importance of surveillance for beta-lactamase-mediated resistance in clinical isolates of Salmonella and highlight the need for continuous monitoring of antibiotic resistance mechanisms in bacterial pathogens. Such information is crucial for guiding antibiotic therapy decisions and implementing effective infection control measures to combat the spread of resistant strains.

Project Overview

<p> 1.1 INTRODUCTION<br>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).<br>Salmonella and Shigella infections represent a major health problem worldwide, particularly in developing 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. Generally Shigella causes bloody diarrhoea while Salmonella induces non-bloody gastroenteritis. Antibiotic resistant Salmonella 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 of antimicrobial 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).<br>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 ?lactamases (ESBLs) encoded on plasmids, as well as on the chromosome (David and Frank 2000). In Gram-negative pathogens, -lactamases remain the most important contributing factor to -lactam resistance, and their increasing prevalence, as well as their alarming evolution seem to be directly linked to the clinical use of novel sub-classes of -lactams (Medeiros, 1997).<br>Beta-lactamases are bacterial enzymes that inactivate -lactam antibiotics by hydrolysis, which result in ineffective compounds (Bush,2001). Beta-lactam antimicrobial agents such as Penicillins, Cephalosporins, monobactams and Carbapenems, are among the most common drugs for the treatment of bacterial infections and account for over 50% of global antibiotic consumption (Kotra, et al., 2007). Bacterial resistance to -lactam antibiotics has significantly increased in recent years and has been attributed to the spread of plasmid mediated ?lactamases. Some of these organisms have produced new forms of the older enzymes such as the extended-spectrum -lactamases (ESBLS) that can hydrolyze newer Cephalosporins and Aztreonam (Paterson and Bromo, 2005).<br>ESBLs are enzymes that mediate resistance to extended spectrum (third generation) Cephalosporins such as Ceftazidime, Cefotaxime and Ceftriaxone as well as Monobactams such as Aztreonam (NCCLS, 1999). These ESBLS have been found worldwide in many different genera of enterobacteriaceae (Bradford, 2001). More than 200 different natural ESBLs variants are known in an increasing variety of Gram-negative species (Bradford, 2001) with their distribution being far from uniform (Marchandin et al., 1999). With -lactams being the <br></p>