Widespread use of beta-lactam antibiotics has promoted the evolution of beta-lactamase mutant enzymes that can hydrolyze ever newer classes of these drugs. Among the most pernicious mutants are the inhibitor-resistant TEM beta-lactamases (IRTs), which elude mechanism-based inhibitors, such as clavulanate. Despite much research on these IRTs, little is known about the structural bases of their a...

OBJECTIVES Recently, resistance to extended-spectrum cephalosporins due to acquired beta-lactamases has been reported in Pseudomonas aeruginosa. The aim of this study was to investigate the prevalence of Ambler class A and D beta-lactamases and their extended-spectrum derivatives and antimicrobial susceptibilities of P. aeruginosa isolated from various parts of Korea. METHODS A total of 252 c...

The enzyme TEM @-lactamase has been used as a model for understanding the pathway leading to formation of inclusion bodies in Escherichia coli. The equilibrium denaturation of TEM p-lactamase revealed that an intermediate that has lost enzymatic activity, native protein fluorescence, and UV absorption, but retains 60% of the native circular dichroism signal, becomes populated at intermediate (1...

The use of beta-lactam antibiotics has led to the evolution and global spread of a variety of resistance mechanisms, including beta-lactamases, a group of enzymes that degrade the beta-lactam ring. The evolution of increased beta-lactam resistance was studied by exposing independent lineages of Salmonella typhimurium to progressive increases in cephalosporin concentration. Each lineage carried ...

We report the case of a pediatric patient with a Salmonella enterica serotype Infantis infection. Detailed microbiological investigation revealed that this isolate carries four beta-lactamase genes (bla(TEM-1b) variant, bla(SHV-5), bla(CTX-M-15), and bla(CMY-2)) conferring resistance to all beta-lactams but imipenem. This is the first report of a Salmonella isolate with CTX-M and AmpC enzymes o...

background :   imipenem-resistant gram negative bacteria, resulting from metallo-beta-lactamase (mbls)-producing strains have been reported to be among the important causes of nosocomial infections and of serious therapeutic problem worldwide. because of their broad range, potent carbapenemase activity and resistance to inhibitors, these enzymes can confer resistance to almost all beta-lactams....

Although TEM-1 beta-lactamase is among the best studied enzymes, its acylation mechanism remains controversial. To investigate this problem, the structure of TEM-1 in complex with an acylation transition-state analogue was determined at ultrahigh resolution (0.85 A) by X-ray crystallography. The quality of the data was such as to allow for refinement to an R-factor of 9.1% and an R(free) of 11....

The aim of this study was to investigate the existence of a β-lactamase gene in a group of multi-drug resistant Acinetobacter baumannii. Twenty strains of multi-drug resistant A. baumannii were isolated. Thirty-four β-lactamase genes and the ISaba1-OXA-23 linkage were analyzed in these strains by polymerase chain reaction (PCR) and verified by DNA sequencing. Three kinds of β-lactamase genes (T...

background extended-spectrum beta-lactamases (esbls) are a group of enzymes that hydrolyze antibiotics, including those containing new cephalosporins, and they are found in a significant percentage of escherichia coli and klebsiella pneumoniae strains. with the widespread use of antibiotics, difficulties with infection therapy caused by drug resistant organisms, especially those that have acqui...