Natural D240G Toho-1 mutant conferring resistance to ceftazidime: biochemical characterization of CTX-M-43
| Autor: | Bernardetta Segatore, Cristina Pellegrini, Domenico Setacci, Chiara Forcella, Massimiliano Aschi, Giuseppe Celenza, Mariagrazia Perilli, Gianfranco Amicosante, Carla Luzi |
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| Rok vydání: | 2008 |
| Předmět: |
Acinetobacter baumannii
Adult Models Molecular Microbiology (medical) Bolivia Carbapenem Imipenem Cefotaxime Mutation Missense Ceftazidime Microbial Sensitivity Tests beta-Lactams Meropenem beta-Lactamases Substrate Specificity chemistry.chemical_compound Escherichia coli polycyclic compounds medicine Humans Pharmacology (medical) Antibacterial agent Pharmacology biology biochemical phenomena metabolism and nutrition bacterial infections and mycoses biology.organism_classification Anti-Bacterial Agents Protein Structure Tertiary Kinetics Infectious Diseases Amino Acid Substitution Biochemistry chemistry Ertapenem Acinetobacter Infections medicine.drug |
| Zdroj: | Journal of Antimicrobial Chemotherapy. 62:991-997 |
| ISSN: | 1460-2091 0305-7453 |
| DOI: | 10.1093/jac/dkn339 |
| Popis: | Objectives: The aim of this article is biochemical and kinetic characterization of CTX-M-43, a natural Asp-240!Gly mutant of CTX-M-44 (ex Toho-1), from a clinical isolate of Acinetobacter baumannii isolated in a Bolivian hospital. Methods: Steady-state kinetic parameters (Km and kcat) were determined for a large pattern of substrates. Analysis of inactivators and transient inactivators was performed to determine the efficiency of acylation (k12/K) and the deacylation constant (k13). Molecular modelling of Michaelis complex of ceftazidime, cefotaxime and ceftibuten, obtained from molecular mechanics calculations, was carried out. Results: CTX-M-43 showed a general increase in affinity towards all cephalosporins tested, with respect to CTX-M-44. Carbapenems acted as inactivators with a good acylation efficiency for meropenem and ertapenem and significant deacylation constant for imipenem. MICs of imipenem obtained at a higher bacterial inoculum of recombinant Escherichia coli were increased. Conclusions: Kinetic data and molecular modelling of Michaelis complex confirmed that Asp-240!Gly allows a better accommodation of the bulky C7b aminothiazol-oxyimino substituent, resulting in a general increase in the enzyme affinity towards oxyimino cephalosporins. The ascertained potentialities of CTX-M-type enzymes, supported by the kinetic data and the behaviour of the recombinant E. coli at different bacterial inocula towards carbapenems, make a possible evolution of those enzymes towards a carbapenemase activity plausible. |
| Databáze: | OpenAIRE |
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