title: Characterization of poxB, a chromosomal-encoded Pseudomonas aeruginosa oxacillinase.
abstract: Pseudomonas aeruginosa is the major pathogen associated with morbidity and mortality of patients with cystic fibrosis. One of the reasons for the failure of beta-lactam antibiotic regimens appears to be mediated by de-regulation of the ampC gene, encoding the chromosomal Ambler's Class C beta-lactamase. Currently, the AmpC is the only known chromosomal beta-lactamase whose expression is regulated by a transcriptional regulator, AmpR. We generated an ampC mutation in the prototypic P. aeruginosa strain PAO1. The mutation in ampC did not abolish the beta-lactamase activity entirely suggesting the expression of yet another unreported beta-lactamase. Our genomic analysis revealed the presence of an open reading frame encoding a protein with high homology to the Class D beta-lactamases, commonly known as oxacillinases. The gene was named poxB for Pseudomonas oxacillinase. Cloning and expression of poxB in Escherichia coli conferred beta-lactam resistance to the host. We detected the presence of poxB both in clinical and environmental isolates. Our studies show that P. aeruginosa possesses two beta-lactamases, AmpC and PoxB, which contribute to its resistance against a wide spectrum of beta-lactam antibiotics.
authors.affiliation: Department of Biological Sciences, Florida International University, University Park, Miami, FL 33199, USA.
authors.forename: Kok-Fai
authors.initials: KF
authors.lastname: Kong
authors.forename: Suriya R
authors.initials: SR
authors.lastname: Jayawardena
authors.forename: Aimee
authors.initials: A
authors.lastname: Del Puerto
authors.forename: Lutz
authors.initials: L
authors.lastname: Wiehlmann
authors.forename: Ulrike
authors.initials: U
authors.lastname: Laabs
authors.forename: Burkhard
authors.initials: B
authors.lastname: Tümmler
authors.forename: Kalai
authors.initials: K
authors.lastname: Mathee
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism; D001483:Base Sequence; D002876:Chromosomes, Bacterial / Q000235:genetics*; D003550:Cystic Fibrosis / Q000382:microbiology / Q000401:mortality; D024881:Drug Resistance, Bacterial / Q000235:genetics*; D004926:Escherichia coli / Q000235:genetics; D015964:Gene Expression Regulation, Bacterial / Q000502:physiology*; D006801:Humans; D008969:Molecular Sequence Data; D010802:Phylogeny; D011552:Pseudomonas Infections / Q000201:enzymology / Q000235:genetics / Q000401:mortality; D011550:Pseudomonas aeruginosa / Q000201:enzymology / Q000235:genetics*; D001618:beta-Lactamases / Q000235:genetics* / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; C071526:AmpR protein, Bacteria; C048795:AmpC beta-lactamases; D001618:beta-Lactamases; C108449:oxacillinase