First kinetic characterization of KluA-9 from a Kluyvera ascorbata clinical strain isolated in Argentina.

GUTKIND GABRIEL; RODRIGUEZ MARGARITA; DI CONZA JOSÉ; POWER PABLO; GALLENI MORENO; AYALA JUAN; RADICE MARCELA

Chicago, USA

Conferencia; 43rd Annual Interscience Conference on Antimicrobial Agents and Chemotherapy - ICAAC; 2003

ASM

  Background: KluA-9 is a chromosome-encoded b-lactamase from Kluyvera ascorbata, closely related to KluA-1 (which was proposed as the putative origin of integron-associated CTX-M-2). Despite they share a close nucleotidic similarity, a thorough kinetic characterization of KluA b-lactamases has not yet been performed. The purpose of this study was to determine the main kinetic parameters of KluA-9, and to correlate these data with those of CTX-M-2, the most prevalent ESBL in Argentina. Methods: Kluyvera ascorbata was isolated in 1995 from a sputum sample in Buenos Aires. The kluA gene was cloned and sequenced, antimicrobial susceptibility of this strain and derived clones, pI and molecular weight of the produced enzyme and their main kinetic parameters determined all by conventional methods. Results: The cloned kluA gene has a 99% nucleotidic identity, and 100% identity in the deduced aminoacidic sequence with KluA-9. Clones where kluA-9-variant was suitably oriented, showed a resistant profile resembling that of a plasmid-borne CTX-M-type enzyme. Conclusion: According to kinetic data, KluA-9 is clearly a cefotaxime-hydrolyzing enzyme, as well as CTX-M enzymes. The resistance phenotype of those clones where kluA-9-variant was oriented in frame with the vector promoter resemble that of bacteria carrying some unusual integrons harboring blaCTX-M. This could be an evidence for the involvement of integrons not only in the mobilization of chromosome-borne genes but also in their expression. Conclusion: According to kinetic data, KluA-9 is clearly a cefotaxime-hydrolyzing enzyme, as well as CTX-M enzymes. The resistance phenotype of those clones where kluA-9-variant was oriented in frame with the vector promoter resemble that of bacteria carrying some unusual integrons harboring blaCTX-M. This could be an evidence for the involvement of integrons not only in the mobilization of chromosome-borne genes but also in their expression. Conclusion: According to kinetic data, KluA-9 is clearly a cefotaxime-hydrolyzing enzyme, as well as CTX-M enzymes. The resistance phenotype of those clones where kluA-9-variant was oriented in frame with the vector promoter resemble that of bacteria carrying some unusual integrons harboring blaCTX-M. This could be an evidence for the involvement of integrons not only in the mobilization of chromosome-borne genes but also in their expression.