Analytical isoelectric focusing of R factor-determined beta-lactamases: correlation with plasmid compatibility

Beta-lactamases: determination of their isoelectric points.

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...

Molecular hybridization versus isoelectric focusing to determine TEM-type beta-lactamases in gram-negative bacteria.

Isoelectric focusing and molecular hybridization with a TEM DNA probe were used to screen for TEM beta-lactamase in 328 bacterial isolates representing 11 gram-negative genera. The TEM enzyme was detected in 50% of isolates, and nine additional types of beta-lactamase could be identified in 36.9% of isolates. The TEM gene was detected in 53.6% of isolates. The results obtained by both methods w...

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...

Isoelectric focusing.

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...