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FEMS Microbiol Lett. 2001 Dec 18;205(2):185-9.

Catalytic and structural properties of IRT-21 beta-lactamase (TEM-77) from a co-amoxiclav-resistant Proteus mirabilis isolate.

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Laboratoire de Bactériologie, CHU, Amiens, France.

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  • FEMS Microbiol Lett 2002 Mar 5;208(2):303-4.


Proteus mirabilis strain MAG1, a clinical isolate that is resistant to broad-spectrum penicillins and co-amoxiclav, produces inhibitor-resistant TEM (IRT)-21, a novel mutant of TEM beta-lactamase. This enzyme has a pI of 5.2 and is derived from the bla(TEM-1a) gene ancestor. It contains two major amino acid substitutions specific for co-amoxiclav resistance (Leu-69 for Met and Ser-244 for Arg) that have never been found together previously. The dramatic loss of sensitivity to clavulanic acid, the enhancement of K(m) for all beta-lactams and markedly for ticarcillin, and the decrease in the catalytic efficiency makes IRT-21 comparable to the other IRTs with substitutions at position 244 or double substitutions.

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