MOTIVATION Beta-lactamases confer resistance to a broad range of antibiotics and inhibitors by accumulating mutations. The number of beta-lactamases and their variants is steadily increasing. The horizontal gene transfer likely plays a major role in dissemination of these markers to new environments and hosts. Moreover, information about the beta-lactamase classes and their variants was scatter...

Beta-lactamases continue to be the leading cause of resistance to beta-lactam antibiotics among gram-negative bacteria. In recent years there has been an increased incidence and prevalence of extended-spectrum beta-lactamases (ESBLs), enzymes that hydrolyze and cause resistance to oxyimino-cephalosporins and aztreonam. The majority of ESBLs are derived from the widespread broad-spectrum beta-la...

Enterobacteriaceae are major pathogens in both hospital and community. Recently the number of MDR phenotypes (multi drug resistant) increased, with the emergence of XDR phenotypes (extremely drug resistant – susceptible only to colistin and tigecycline). It is extremely important to detect and correct the reporting mechanisms for resistance. Many clinical laboratories have problems detecting ex...

The expression of resistance to cephalosporins is highly varied and due to various mechanisms. The greatest disadvantage of the cephalosporins is that they are inactivated by the array of beta-lactamases produced by bacteria. The high levels of chromosomal enzymes produced by these organisms are a major cause of cephalosporin resistance. Plasmid-mediated beta-lactamases (PMBLs) have also been i...

We assessed the extent and mechanisms of antagonism of beta-lactam antibiotics by cefoxitin. In tests with 41 gram-negative isolates, cefoxitin antagonized cephalothin, cefamandole, cefsulodin, cefotaxime, moxalactam, ampicillin, carbenicillin, piperacillin, mezlocillin, and azlocillin, but not cephalexin, mecillinam, or N-formimidoyl thienamycin. The extent of antagonism varied with the beta-l...

objective(s) resistance to the new generation of cephalosporins which is mediated by extended-spectrum beta-lactamases (esbls) has been found among escherichia coli isolates throughout the world. these resistance genes and their producers, the micro-organisms carrying beta-lactamases, are responsible for serious clinical and therapeutic problems among inpatients and it is necessary to pay more ...

abstract background: pseudomonas aeruginosa is one of the most common gram negative bacteria involved in nosocomial infections. presence of extended-spectrum beta-lactamases (esbls) genes, play an important role in induction of resistance in beta-lactamase producing species to beta lactam antibiotics. frequency of resistance to these antibiotics is increasing. in this study, antibiotic sensitiv...

Resistance to beta-lactam antibiotics has been a problem for as long as these drugs have been used in clinical practice. In clinically significant bacteria the most important mechanism of resistance is the production of one or more beta-lactamases, enzymes that hydrolyse the beta-lactam bond characteristic of this family of antibiotics. Prominent among the beta-lactamases produced by the Entero...

Most methicillin-resistant Staphylococcus aureus (MRSA) strains produce beta-lactamase. To determine whether this enzyme(s) is identical to one or more of the four beta-lactamases produced by methicillin-susceptible strains, the beta-lactamases of 50 MRSA isolates were typed by using substrate profile analysis. Forty type A, no type B, ten type C, and no type D beta-lactamase-producing strains ...