TLA-1: a new plasmid-mediated extended-spectrum beta-lactamase from Escherichia coli.
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 bla(TLA-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: (70)SXXK, (130)SDN, and (234)KTG. 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.
Silva
J
J
Departamento de Resistencia Bacteriana, Instituto Nacional de Salud Pública, Centro de Investigaciones Sobre Enfermedades Infecciosas, Cuernavaca, Morelos, México. jsilva@insp3.insp.mx
Aguilar
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Ayala
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Estrada
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Garza-Ramos
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Lara-Lemus
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Ledezma
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D000595:Amino Acid Sequence; D001483:Base Sequence; D002439:Cefotaxime / Q000378:metabolism; D002511:Cephalosporins / Q000494:pharmacology; D003001:Cloning, Molecular; D003227:Conjugation, Genetic / Q000235:genetics; D004926:Escherichia coli / Q000187:drug effects / Q000201:enzymology* / Q000235:genetics*; D004927:Escherichia coli Infections / Q000382:microbiology; D006801:Humans; D007525:Isoelectric Focusing; D007700:Kinetics; D008800:Mexico; D008826:Microbial Sensitivity Tests; D008969:Molecular Sequence Data; D010957:Plasmids / Q000235:genetics*; D001618:beta-Lactamases / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*
D002511:Cephalosporins; C407005:TLA-1 beta-lactamase; D001618:beta-Lactamases; D002439:Cefotaxime