TEM-109 (CMT-5), a natural complex mutant of TEM-1 beta-lactamase combining the amino acid substitutions of TEM-6 and TEM-33 (IRT-5).
Escherichia coli CF349 exhibited a complex beta-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 beta-lactamase of pI 5.9. The corresponding bla gene was identified by PCR and sequencing as a bla(TEM) gene. The deduced protein sequence revealed a new complex mutant of TEM-1 beta-lactamase designated TEM-109 (CMT-5). TEM-109 contained both the substitutions Glu104Lys and Arg164His of the expanded-spectrum beta-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 (k(cat), 56 s(-1) and 105 s(-1), respectively; K(m) values, 226 and 247 microM, respectively). The 50% inhibitory concentrations of clavulanate and tazobactam (0.13 microM and 0.27 microM, respectively) were 5- to 10-fold higher for TEM-109 than for TEM-6 (0.01 and 0.06 microM, 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.
Robin
F
F
Faculté de Médecine, Centre Hospitalo-Universitaire, Clermont-Ferrand, France. frobin@chu-clermontferrand.fr
Delmas
J
J
Chanal
C
C
Sirot
D
D
Sirot
J
J
Bonnet
R
R
D019943:Amino Acid Substitution; D004926:Escherichia coli / Q000187:drug effects / Q000201:enzymology* / Q000235:genetics; D006801:Humans; D008826:Microbial Sensitivity Tests; D009154:Mutation; D016133:Polymerase Chain Reaction; D017422:Sequence Analysis, DNA; D018440:beta-Lactam Resistance; D001618:beta-Lactamases / Q000737:chemistry* / Q000235:genetics*
C073183:beta-lactamase TEM-6; D001618:beta-Lactamases; C034413:beta-lactamase TEM-1