title: Pseudomonas aeruginosa isolates from patients with cystic fibrosis have different beta-lactamase expression phenotypes but are homogeneous in the ampC-ampR genetic region.
abstract: Pseudomonas aeruginosa isolates from 1 of 17 cystic fibrosis patients produced secondary beta-lactamase in addition to the ampC beta-lactamase. Isolates were grouped into three beta-lactamase expression phenotypes: (i) beta-lactam sensitive, low basal levels and inducible beta-lactamase production; (ii) beta-lactam resistant, moderate basal levels and hyperinducible beta-lactamase production; (iii) beta-lactam resistant, high basal levels and constitutive beta-lactamase production. Apart from a base substitution in the ampR-ampC intergenic region of an isolate with moderate-basal-level and hyperinducible beta-lactamase production, sensitive and resistant strains were identical in their ampC-ampR genetic regions. Thus, enhanced beta-lactamase expression is due to mutations in regulatory proteins other than AmpR.
authors.affiliation: Institute of Medical Microbiology & Immunology, Panum Institute, University of Copenhagen, Denmark.
authors.forename: J I
authors.initials: JI
authors.lastname: Campbell
authors.forename: O
authors.initials: O
authors.lastname: Ciofu
authors.forename: N
authors.initials: N
authors.lastname: Høiby
mesh_terms: D002908:Chronic Disease; D003550:Cystic Fibrosis / Q000382:microbiology*; D004269:DNA, Bacterial / Q000235:genetics; D005784:Gene Amplification; D005798:Genes, Bacterial; D006801:Humans; D009154:Mutation; D010641:Phenotype; D010957:Plasmids; D011401:Promoter Regions, Genetic; D011550:Pseudomonas aeruginosa / Q000187:drug effects / Q000201:enzymology* / Q000235:genetics*; D015183:Restriction Mapping; D018440:beta-Lactam Resistance; D001618:beta-Lactamases / Q000235:genetics* / Q000378:metabolism*
chemical_list: D004269:DNA, Bacterial; D001618:beta-Lactamases