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Antimicrobial Agents and Chemotherapy, April 2000, p. 997-1003, Vol. 44, No. 4
0066-4804/00/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.

TLA-1: a New Plasmid-Mediated Extended-Spectrum beta -Lactamase from Escherichia coli

J. Silva,1,* C. Aguilar,1,dagger G. Ayala,2 M. A. Estrada,1 U. Garza-Ramos,1 R. Lara-Lemus,2 and L. Ledezma1

Departamento de Resistencia Bacteriana1 and Departamento de Bioquímica de Patógenos,2 Instituto Nacional de Salud Pública, Centro de Investigaciones Sobre Enfermedades Infecciosas, Cuernavaca, Morelos, México

Received 29 April 1999/Returned for modification 20 December 1999/Accepted 14 January 2000

Escherichia coli R170, isolated from the urine of an infected patient, was resistant to expanded-spectrum cephalosporins, aztreonam, ciprofloxacin, and ofloxacin but was susceptible to amikacin, cefotetan, and imipenem. This particular strain contained three different plasmids that encoded two beta -lactamases with pIs of 7.0 and 9.0. Resistance to cefotaxime, ceftazidime, aztreonam, trimethoprim, and sulfamethoxazole was transferred by conjugation from E. coli R170 to E. coli J53-2. The transferred plasmid, RZA92, which encoded a single beta -lactamase, was 150 kb in length. The cefotaxime resistance gene that encodes the TLA-1 beta -lactamase (pI 9.0) was cloned from the transconjugant by transformation to E. coli DH5alpha . Sequencing of the blaTLA-1 gene revealed an open reading frame of 906 bp, which corresponded to 301 amino acid residues, including motifs common to class A beta -lactamases: 70SXXK, 130SDN, and 234KTG. The amino acid sequence of TLA-1 shared 50% identity with the CME-1 chromosomal class A beta -lactamase from Chryseobacterium (Flavobacterium) meningosepticum; 48.8% identity with the VEB-1 class A beta -lactamase from E. coli; 40 to 42% identity with CblA of Bacteroides uniformis, PER-1 of Pseudomonas aeruginosa, and PER-2 of Salmonella typhimurium; and 39% identity with CepA of Bacteroides fragilis. The partially purified TLA-1 beta -lactamase had a molecular mass of 31.4 kDa and a pI of 9.0 and preferentially hydrolyzed cephaloridine, cefotaxime, cephalothin, benzylpenicillin, and ceftazidime. The enzyme was markedly inhibited by sulbactam, tazobactam, and clavulanic acid. TLA-1 is a new extended-spectrum beta -lactamase of Ambler class A.

* Corresponding author. Mailing address: Departamento de Resistencia Bacteriana, CISEI, Av. Universidad 655, Colonia Santa María Ahuacatitlán, 62508, Cuernavaca, Morelos, México. Phone: (52) 73-29-30-21. Fax: (52) 73-17-54-85. E-mail: jsilva{at}insp3.insp.mx.

dagger Present address: Instituo de Investigaciones Biomédicas. Dpto. de Biotecnología. Circuito Escolar, Ciudad Universitaria, UNAM, México, D.F. C.P. 04510, Mexico.

Antimicrobial Agents and Chemotherapy, April 2000, p. 997-1003, Vol. 44, No. 4
0066-4804/00/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.


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