title: Impact of AmpC overexpression on outcomes of patients with Pseudomonas aeruginosa bacteremia.
abstract: AmpC overexpression (AmpC++) is a significant mechanism of beta-lactam resistance in Pseudomonas aeruginosa, but its impact on clinical outcomes is not well established. To examine the influence of AmpC++ on clinical outcomes of patients with P. aeruginosa bacteremia, we screened all bloodstream P. aeruginosa isolates obtained from 2003 to 2006 for AmpC++. Demographics and outcomes were retrospectively compared between patients with P. aeruginosa bacteremia caused by AmpC++ and pan-susceptible strains (wild-type controls). Of the 263 isolates screened, 63 (24.0%) were nonsusceptible to ceftazidime. Clinical data of 42 AmpC++ isolates from 21 patients were compared with 33 control patients. The 2 groups were similar in sex and race. Patients in the AmpC++ group was more likely to receive inappropriate empiric antibiotics (odds ratio [OR] = 67.5; 95% confidence interval [CI], 6.3-720.0) and experience microbiologic persistence (OR = 12.2; 95% CI, 1.7-87.7). In institutions with a high prevalence of AmpC++, empiric therapy with agents with activity against AmpC++ strains may be warranted.
authors.affiliation: University of Houston College of Pharmacy, TX 77030, USA. vtam@uh.edu
authors.forename: Vincent H
authors.initials: VH
authors.lastname: Tam
authors.forename: Kai-Tai
authors.initials: KT
authors.lastname: Chang
authors.forename: Amy N
authors.initials: AN
authors.lastname: Schilling
authors.forename: Mark T
authors.initials: MT
authors.lastname: LaRocco
authors.forename: Layne O
authors.initials: LO
authors.lastname: Genty
authors.forename: Kevin W
authors.initials: KW
authors.lastname: Garey
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000900:Anti-Bacterial Agents / Q000627:therapeutic use*; D016470:Bacteremia / Q000188:drug therapy* / Q000382:microbiology*; D001426:Bacterial Proteins / Q000096:biosynthesis*; D005260:Female; D015870:Gene Expression; D006801:Humans; D008297:Male; D008875:Middle Aged; D011552:Pseudomonas Infections / Q000188:drug therapy* / Q000382:microbiology; D011550:Pseudomonas aeruginosa / Q000187:drug effects / Q000201:enzymology*; D012189:Retrospective Studies; D016896:Treatment Outcome; D018440:beta-Lactam Resistance; D001618:beta-Lactamases / Q000096:biosynthesis*
chemical_list: D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; C048795:AmpC beta-lactamases; D001618:beta-Lactamases