title: Characterisation of KLUA-9, a beta-lactamase from extended-spectrum cephalosporin-susceptible Kluyvera ascorbata, and genetic organisation of bla(KLUA-9).
abstract: This study characterised the genetic environment of the chromosomally encoded bla(KLUA-9) gene from a clinical Kluyvera ascorbata isolate and performed a kinetic characterisation of KLUA-9. Purified KLUA-9 showed the highest catalytic efficacies towards benzylpenicillin, ampicillin, piperacillin, first-generation cephalosporins, cefuroxime and cefoperazone; like other 'cefotaximases', it showed a much higher rate of hydrolysis of cefotaxime than ceftazidime, whilst dicloxacillin, cefoxitin and imipenem behaved as poor substrates. A 9kb insert from K. ascorbata was cloned (Escherichia coli KK68C1) and sequenced. bla(KLUA-9) and its 266bp upstream flanking region (almost identical to the integron-associated bla(CTX-M-2)) are preceded by an aspat variant, a ypdABC-like operon and two open reading frames with unknown functions. Unlike ISCR1-associated bla(CTX-M-2) genes, we failed to detect the putative orf513 recombination sites. Instead, we were able to localise the 5bp target sites for insertion of ISEcp1B, suggesting that this element could be responsible for future (or still undetected) mobilisation of bla(KLUA-9) to more efficiently transferred elements.
authors.affiliation: Cátedra de Microbiología, Facultad de Farmacia y Bioquímica, Universidad de Buenos Aires, Junín 954 (1113), Buenos Aires, Argentina.
authors.forename: María Margarita
authors.initials: MM
authors.lastname: Rodríguez
authors.forename: Pablo
authors.initials: P
authors.lastname: Power
authors.forename: Cédric
authors.initials: C
authors.lastname: Bauvois
authors.forename: José
authors.initials: J
authors.lastname: Di Conza
authors.forename: Juan A
authors.initials: JA
authors.lastname: Ayala
authors.forename: Moreno
authors.initials: M
authors.lastname: Galleni
authors.forename: Gabriel
authors.initials: G
authors.lastname: Gutkind
mesh_terms: D001483:Base Sequence; D018550:Cephalosporin Resistance / Q000235:genetics; D002511:Cephalosporins / Q000378:metabolism / Q000494:pharmacology*; D004269:DNA, Bacterial / Q000235:genetics; D024881:Drug Resistance, Bacterial / Q000235:genetics; D004756:Enterobacteriaceae Infections / Q000382:microbiology; D019143:Evolution, Molecular; D005798:Genes, Bacterial; D006801:Humans; D066298:In Vitro Techniques; D007700:Kinetics; D044086:Kluyvera / Q000187:drug effects / Q000201:enzymology* / Q000235:genetics* / Q000302:isolation & purification; D008969:Molecular Sequence Data; D010957:Plasmids / Q000235:genetics; D001618:beta-Lactamases / Q000235:genetics* / Q000378:metabolism
chemical_list: D002511:Cephalosporins; D004269:DNA, Bacterial; D001618:beta-Lactamases