title: Characterization of an extended-spectrum class A β-lactamase from a novel enterobacterial species taxonomically related to Rahnella spp./Ewingella spp.
abstract: OBJECTIVE
  To characterize the naturally occurring β-lactamase gene identified from a clinical isolate belonging to a novel enterobacterial species that is closely related to Rahnella spp. and Ewingella spp.
  
  
  METHODS
  Shotgun cloning and expression in Escherichia coli were performed in order to characterize this resistance determinant. Enzymatic activities were measured by UV spectrophotometry after an ion-exchange chromatography purification procedure.
  
  
  RESULTS
  A chromosomal gene coding for the extended-spectrum β-lactamase (ESBL) SMO-1 was identified from a novel enterobacterial species that is taxonomically related to Rahnella aquatilis and Ewingella americana. The β-lactamase efficiently hydrolysed penicillins and cefotaxime, and shared 75% amino acid identity with the plasmid-mediated β-lactamase SFO-1 from Serratia fonticola, 74% amino acid identity with the plasmid-mediated ESBL CTX-M-2 originating from Kluyvera spp. and 72% amino acid identity with the chromosomally encoded and intrinsic RAHN-1 from R. aquatilis.
  
  
  CONCLUSIONS
  We have identified a novel enterobacterial species recovered from a clinical specimen, constituting another potential source of acquired ESBL. The ESBL shared significant similarities with the CTX-M-type enzymes.
authors.affiliation: INSERM U914 "Emerging Resistance to Antibiotics", Faculté de Médecine et Université Paris Sud, 94275 K.-Bicêtre, France. laurent.poirel@bct.aphp.fr
authors.forename: Marie-Frédérique
authors.initials: MF
authors.lastname: Lartigue
authors.forename: Patrice
authors.initials: P
authors.lastname: Nordmann
authors.forename: Mikhail V
authors.initials: MV
authors.lastname: Edelstein
authors.forename: Gaëlle
authors.initials: G
authors.lastname: Cuzon
authors.forename: Sylvain
authors.initials: S
authors.lastname: Brisse
authors.forename: Laurent
authors.initials: L
authors.lastname: Poirel
mesh_terms: D002439:Cefotaxime / Q000378:metabolism; D002852:Chromatography, Ion Exchange; D003001:Cloning, Molecular; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics; D004755:Enterobacteriaceae / Q000145:classification / Q000201:enzymology* / Q000235:genetics / Q000302:isolation & purification; D004756:Enterobacteriaceae Infections / Q000382:microbiology; D004926:Escherichia coli / Q000235:genetics; D015870:Gene Expression; D006801:Humans; D006868:Hydrolysis; D008969:Molecular Sequence Data; D010406:Penicillins / Q000378:metabolism; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid; D013056:Spectrophotometry, Ultraviolet; D001618:beta-Lactamases / Q000235:genetics* / Q000302:isolation & purification / Q000378:metabolism*
chemical_list: D004269:DNA, Bacterial; D010406:Penicillins; D001618:beta-Lactamases; D002439:Cefotaxime
keywords: CTX-M; Gram-negatives; extended-spectrum β-lactamases