The bla(TEM-1) beta-lactamase gene has become widespread due to the selective pressure of beta-lactam use and its stable maintenance on transferable DNA elements. In contrast, bla(SME-1) is rarely isolated and is confined to the chromosome of carbapenem-resistant Serratia marcescens strains. Dissemination of bla(SME-1) via transfer to a mobile DNA element could hinder the use of carbapenems. In...

Resistance to β-lactam/β-lactamase inhibitors in enterobacteria is a growing problem that has not been intensively studied in Argentina. In the present work, 54/843 enterobacteria collected in a teaching hospital of Buenos Aires city were ampicillin-sulbactam-resistant isolates remaining susceptible to second- and third-generation cephalosporins. The enzymatic mechanisms present in the isolates...

In Gram-negative bacteria, TEM-1 beta-lactamase provides the major mechanism of plasmid-mediated beta-lactam resistance. Natural variants of TEM-1 with increased antibiotic resistance have appeared in response to the use of extended-spectrum beta-lactam antibiotics (e.g., ceftazidime) and beta-lactamase inhibitors (e.g., clavulanic acid). Some of the variant enzymes are more efficient at cataly...

Escherichia coli is a common cause of infections in companion animals. In recent years the increasing prevalence of resistance to β-lactams, including extended-spectrum cephalosporins, antimicrobials frequently used in small animal veterinary practice, was observed in canine isolates of E. coli. The aim of this study was to detect and to characterize extended-spectrum β-lactamases (ESBLs) produ...

The beta-lactamases of six strains of Acinetobacter baumannii were investigated using analytical isoelectric focusing, and the MIC values for 16 beta-lactam antibiotics determined against the strains. Three strains produced a chromosomal cephalosporinase (pI > 8.5), one strain a CARB-5 beta-lactamase (pI = 6.35), one strain a TEM-1 penicillinase (pI = 5.4) as well as a cephalosporinase (pI > 8....

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...

b-Lactamases are an important family of bacterial enzymes for research in bacterial infection and biotechnology. Bacterial resistance to antibiotics is becoming a growing global health problem, and bacteria expressing b-lactamases are resistant to b-lactam antibiotics because b-lactamases efficiently hydrolyze b-lactam antibiotics such as penicillins and cephalosporins. Rapid and sensitive dete...