Genetic and Kinetic Characterization of the Novel AmpC beta-Lactamases DHA-6 and DHA-7
Por:
Perez-Llarena, FJ, Zamorano, L, Kerff, F, Beceiro, A, Garcia, P, Miro, E, Larrosa, N, Gomez-Bertomeu, F, Mendez, JA, Gonzalez-Lopez, JJ, Oliver, A, Galleni, M, Navarro, F, Bou, G
Publicada:
1 nov 2014
Resumen:
During a Spanish surveillance study, two natural variants of DHA beta-lactamases, DHA-6 and DHA-7, were found, with the replacements Ala226Thr and Phe322Ser, respectively, with respect to DHA-1. The DHA-6 and DHA-7 enzymes were isolated from Escherichia coli and Enterobacter cloacae clinical isolates, respectively. The aim of this study was to genetically, microbiologically, and biochemically characterize the DHA-6 and DHA-7 beta-lactamases. The bla(DHA-6) and bla(DHA-7) genes were located in the I1 and HI2 incompatibility group plasmids of 87.3 and 310.4 kb, respectively. The genetic contexts of bla(DHA-6) and bla(DHA-7) were similar to that already described for the bla(DHA-1) gene and included the qnrB4 and aadA genes. The MICs for cephalothin, aztreonam, cefotaxime, and ceftazidime were 8- to 32-fold lower for DHA-6 than for DHA-1 or DHA-7 expressed in the same isogenic E. coli TG1 strain. Interestingly, the MIC for cefoxitin was higher in the DHA-6-expressing transformant than in DHA-1 or DHA-7. Biochemical studies with pure beta-lactamases revealed slightly lower catalytic efficiencies of DHA-6 against cephalothin, ceftazidime, and cefotaxime than those of DHA-1 and DHA-7. To understand this behavior, stability experiments were carried out and showed that the DHA-6 protein displayed significantly higher stability than the DHA-1 and DHA-7 enzymes. The proximity of Thr226 to the N terminus in the tertiary protein structure in DHA-6 may promote this stabilization and, consequently, may induce a slight reduction in the dynamic of this enzyme that primarily affects the hydrolysis of some of the bulkiest antibiotics.
Filiaciones:
Perez-Llarena, FJ:
Complejo Hosp Univ A Coruna, Serv Microbiol INIBIC, La Coruna, Spain
Zamorano, L:
Inst Invest Sanitaria Palma IdISPa, Hosp Son Espases, Microbiol Serv, Palma De Mallorca, Spain
Kerff, F:
Univ Liege, Ctr Ingn Prot, Liege, Belgium
Beceiro, A:
Complejo Hosp Univ A Coruna, Serv Microbiol INIBIC, La Coruna, Spain
Garcia, P:
Complejo Hosp Univ A Coruna, Serv Microbiol INIBIC, La Coruna, Spain
Miro, E:
Univ Autonoma Barcelona, Hosp Santa Creu & St Pau IIB St Pau, Microbiol Serv, E-08193 Barcelona, Spain
Larrosa, N:
Univ Autonoma Barcelona, Hosp Vall dHebron, Microbiol Serv, E-08193 Barcelona, Spain
Gomez-Bertomeu, F:
Hosp Univ Joan XXIII Tarragona, Microbiol Serv, Tarragona, Spain
Mendez, JA:
Complejo Hosp Univ A Coruna, Serv Microbiol INIBIC, La Coruna, Spain
Gonzalez-Lopez, JJ:
Univ Autonoma Barcelona, Hosp Vall dHebron, Microbiol Serv, E-08193 Barcelona, Spain
Oliver, A:
Inst Invest Sanitaria Palma IdISPa, Hosp Son Espases, Microbiol Serv, Palma De Mallorca, Spain
Galleni, M:
Univ Liege, Ctr Ingn Prot, Liege, Belgium
Navarro, F:
Univ Autonoma Barcelona, Hosp Santa Creu & St Pau IIB St Pau, Microbiol Serv, E-08193 Barcelona, Spain
Bou, G:
Complejo Hosp Univ A Coruna, Serv Microbiol INIBIC, La Coruna, Spain
Green Published, Bronze
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