Molecular Specificities of R Factor-Determined Beta-Lactamases: Correlation with Plasmid Compatibility

Characterization of R factor beta-lactamases by the acidimetric method.

The properties and regulation of beta-lactamases produced by certain R factors derived from ampicillin-resistant strains of Escherichia coli and Klebsiella were characterized. beta-Lactamase activity was determined by the acidimetric method with phenol red as indicator. The sensitivity of this assay was increased by employing phosphate buffer at a final concentration of 0.4 mm; as little as 0.0...

Plasmid-mediated carbencillin hydrolyzing beta-lactamases of Proteus mirabilis.

Since ABRAHAM and CHAIN') reported the production of beta((l)-lactamase by Escherichia coli, penicillinases have been shown to play an important role in the resistance of organisms against (3lactam antibiotics2.3). In many cases, the 46lactamases of Gram-negative bacteria have been shown to be mediated by R plasmids'), in contrast to chromosomally encoded drug resistance'). 46-Lactamases of Pro...

A functional classification scheme for beta-lactamases and its correlation with molecular structure.

Sequences of homologous beta-lactamases from clinical isolates of Serratia marcescens with different substrate specificities.

Genes for two group 1 beta-lactamases, SRT-1 and SST-1, were sequenced. These beta-lactamases were produced by clinical isolates of Serratia marcescens, isolates GN16694 and GN19450, respectively. The resulting enzymes were 96% identical. SRT-1 hydrolyzed oxyimino cephalosporins, but SST-1 hardly hydrolyzed them. At residue 213 in the third motif, which is conserved among group 1 beta-lactamase...

Extended-Spectrum-Beta-Lactamases, AmpC Beta-Lactamases and Plasmid Mediated Quinolone Resistance in Klebsiella spp. from Companion Animals in Italy

We report the genetic characterization of 15 Klebsiella pneumoniae (KP) and 4 isolates of K. oxytoca (KO) from clinical cases in dogs and cats and showing extended-spectrum cephalosporin (ESC) resistance. Extended spectrum beta-lactamase (ESBL) and AmpC genes, plasmid-mediated quinolone resistance (PMQR) and co-resistances were investigated. Among KP isolates, ST101 clone was predominant (8/15,...