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Antimicrobial Agents and Chemotherapy, November 2005, p. 4443-4447, Vol. 49, No. 11
0066-4804/05/$08.00+0     doi:10.1128/AAC.49.11.4443-4447.2005
Copyright © 2005, American Society for Microbiology. All Rights Reserved.

TEM-109 (CMT-5), a Natural Complex Mutant of TEM-1 ß-Lactamase Combining the Amino Acid Substitutions of TEM-6 and TEM-33 (IRT-5){dagger}

F. Robin,* J. Delmas, C. Chanal, D. Sirot, J. Sirot, and R. Bonnet

Faculté de Médecine, Centre Hospitalo-Universitaire, Clermont-Ferrand, France

Received 30 March 2005/ Returned for modification 6 June 2005/ Accepted 3 August 2005

Escherichia coli CF349 exhibited a complex ß-lactam resistance phenotype, including resistance to amoxicillin and ticarcillin alone and in combination with clavulanate and to some extended-spectrum cephalosporins. The double-disk synergy test was positive. CF349 harbored an 85-kb conjugative plasmid which encoded a ß-lactamase of pI 5.9. The corresponding bla gene was identified by PCR and sequencing as a blaTEM gene. The deduced protein sequence revealed a new complex mutant of TEM-1 ß-lactamase designated TEM-109 (CMT-5). TEM-109 contained both the substitutions Glu104Lys and Arg164His of the expanded-spectrum ß-lactamase (ESBL) TEM-6 and Met69Leu of the inhibitor-resistant TEM-33 (IRT-5). TEM-109 exhibited hydrolytic activity against ceftazidime similar to that of TEM-6 (kcat, 56 s–1 and 105 s–1, respectively; Km values, 226 and 247 µM, respectively). The 50% inhibitory concentrations of clavulanate and tazobactam (0.13 µM and 0.27 µM, respectively) were 5- to 10-fold higher for TEM-109 than for TEM-6 (0.01 and 0.06 µM, respectively) but were almost 10-fold lower than those for TEM-33. The characterization of this novel CMT, which exhibits a low level of resistance to inhibitors, highlights the emergence of this new ESBL type.

* Corresponding author. Mailing address: Laboratoire de Bactériologie, Faculté de Médecine, 28 place H. Dunant, 63 001 Clermont-Ferrand, France. Phone: (33) 4 73 17 81 50. Fax: (33) 4 73 27 74 94. E-mail: frobin{at}chu-clermontferrand.fr.

{dagger} This paper is devoted to the memory of Catherine Chanal.

Antimicrobial Agents and Chemotherapy, November 2005, p. 4443-4447, Vol. 49, No. 11
0066-4804/05/$08.00+0     doi:10.1128/AAC.49.11.4443-4447.2005
Copyright © 2005, American Society for Microbiology. All Rights Reserved.



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