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Antimicrobial Agents and Chemotherapy, May 2002, p. 1183-1189, Vol. 46, No. 5
0066-4804/02/$04.00+0     DOI: 10.1128/AAC.46.5.1183-1189.2002
Copyright © 2002, American Society for Microbiology. All Rights Reserved.

TEM-80, a Novel Inhibitor-Resistant ß-Lactamase in a Clinical Isolate of Enterobacter cloacae

Corinne Arpin,^1* Roger Labia,² Véronique Dubois,¹ Patrick Noury,³ Muriel Souquet,⁴ and Claudine Quentin¹

Laboratoire de Microbiologie, Université de Bordeaux 2, 33076 Bordeaux Cedex,¹ CNRS-UBO-MNHN, Unité FRE 2125, 29000 Quimper,² Laboratoire d'Analyses Médicales,³ Home Marie Curie, 33140 Villenave d'Ornon, France⁴

Received 19 June 2001/ Returned for modification 29 September 2001/ Accepted 13 January 2002

Enterobacter cloacae Ecl261 was isolated with Escherichia coli Ec257 from the urine of a patient living in a nursing home. Both isolates were resistant to ticarcillin (MICs, 1,024 µg/ml), without significant potentiation of its activity by 2 µg of clavulanate per ml (MICs, 512 µg/ml), and susceptible to naturally active cephalosporins. This inhibitor-resistant phenotype was conferred in both strains by similar conjugative plasmids of 40 kb (Ecl261) and 30 kb (Ec257), which also conveyed resistance to sulfonamides and trimethoprim. Clinical and transconjugant strains produced a ß-lactamase with a pI of 5.2 which belonged to the TEM family, as indicated by specific PCR amplification. Compared with TEM-1, this enzyme exhibited lower catalytic efficiencies (14- and 120-fold less for amoxicillin and ticarcillin, respectively), and higher concentrations of ß-lactamase inhibitors were required to yield a 50% reduction in benzylpenicillin hydrolysis (750-, 82-, and 50-fold higher concentrations for clavulanate, sulbactam, and tazobactam, respectively). Gene sequencing revealed four nucleotide differences with the nucleotide sequence of bla_TEM-1A. The first replacement (T32C), located in the promoter region, was described as being responsible for the increase in the level of ß-lactamase production. The three other changes led to amino acid substitutions that define a new inhibitor-resistant TEM (IRT) ß-lactamase, TEM-80 (alternate name, IRT-24). Two of them, Met69Leu and Asn276Asp, have previously been related to inhibitor resistance. The additional mutation, Ile127Val, was demonstrated by site-directed mutagenesis to have a very weak effect, at least alone, on the IRT phenotype. This is the first description of an IRT ß-lactamase in E. cloacae. The horizontal transfer of bla_TEM-80 may have occurred either from Ec257 to Ecl261 or in the reverse order.

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* Corresponding author. Mailing address: Laboratoire de Microbiologie, Faculté de Pharmacie, Université de Bordeaux 2, 146 rue Léo Saignat, 33076 Bordeaux Cedex, France. Phone: (33) 5 57 57 10 75. Fax: (33) 5 56 90 90 72. E-mail: corinne.arpin{at}bacterio.u-bordeaux2.fr.

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Antimicrobial Agents and Chemotherapy, May 2002, p. 1183-1189, Vol. 46, No. 5
0066-4804/02/$04.00+0     DOI: 10.1128/AAC.46.5.1183-1189.2002
Copyright © 2002, American Society for Microbiology. All Rights Reserved.

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