Important discrepancies in isoelectric points (pI) of beta-lactamases were observed depending on the experimental procedure used for their determination: isoelectric focusing (IEF) in sucrose density gradients or analytical IEF in thin-layer polyacrylamide gels (PA). The variations, negligable in the case of TEM-like beta-lactamases, appeared to be important in the case of cephalosporinases and...

BACKGROUND Streptococcus pneumoniae, Streptococcus pyogenes and Haemophilus influenzae are bacteria present in the nasopharynx as part of normal flora. The ecological equilibrium in the nasopharynx can be disrupted by the presence of antibiotics. METHODOLOGY/PRINCIPAL FINDINGS A computerized two-compartment pharmacodynamic model was used to explore beta-lactam effects on the evolution over ti...

Bacterial beta-lactamases are the major causes of resistance to beta-lactam antibiotics. Three classes of these enzymes are believed to have evolved from ancestral penicillin-binding proteins (PBPs), enzymes responsible for bacterial cell wall biosynthesis. Both beta-lactamases and PBPs are able to efficiently form acyl-enzyme species with beta-lactam antibiotics. In contrast to beta-lactamases...

Since the first communication describing an organism that produces an enzyme capable of hydrolyzing extended-spectrum cephalosporins (5, 6), several outbreaks of Enterobacte-riaceae resistant to oxyimino-␤-lactams have been reported. In these cases, the adopted survival strategy of bacteria challenged by the introduction of aztreonam, cefotaxime, ceftazi-dime, and other oxyimino-␤-lactams was t...

BACKGROUND Antibiotic resistance is a growing problem worldwide. Mechanisms of resistance vary, and some can confer resistance to multiple classes of antibiotics. OBJECTIVE To characterise the antibiotic resistance profiles of Escherichia coli isolates obtained from stool samples of young rural children exposed or unexposed to antibiotics. METHODOLOGY The samples were collected from childre...

Production of extended-spectrum beta-lactamase (ESBL) is one of the most important resistance mechanisms that hamper the antimicrobial treatment of infections caused by Enterobacteriaceae. ESBLs are classified into several groups according to their amino-acid sequence homology. While TEM and SHV enzymes were the most common ESBLs in the 1990s, CTX-M enzymes have spread rapidly among Enterobacte...

Antibiotics that are excreted into the intestinal tract promote antibiotic resistance by exerting selective pressure on the gut microbiota. Using a beagle dog model, we show that an orally administered targeted recombinant beta-lactamase enzyme eliminates the portion of parenteral ampicillin that is excreted into the small intestine, preventing ampicillin-induced changes to the fecal microbiota...

A method to delete in-phase codons throughout a defined target region of a gene has been developed. This approach, named the codon-based random deletion (COBARDE) method, is able to delete complete codons in a random and combinatorial mode. Robustness, automation and fine-tuning of the mutagenesis rate are essential characteristics of the method, which is based on the assembly of oligonucleotid...

BACKGROUND We investigated the prevalence of plasmid-mediated quinolone resistance and its association with extended-spectrum beta-lactamase (ESBL) and AmpC beta-lactamase in Enterobacteriaceae. METHODS A total of 347 non-duplicated isolates of Enterobacteriaceae were collected between August and October 2006 from 2 hospitals. Qnr determinant screening was conducted using PCR amplification, a...