title: Prevalence, resistance mechanisms, and susceptibility of multidrug-resistant bloodstream isolates of Pseudomonas aeruginosa.
abstract: Pseudomonas aeruginosa is an important pathogen commonly implicated in nosocomial infections. The occurrence of multidrug-resistant (MDR) P. aeruginosa strains is increasing worldwide and limiting our therapeutic options. The MDR phenotype can be mediated by a variety of resistance mechanisms, and the corresponding relative biofitness is not well established. We examined the prevalence, resistance mechanisms, and susceptibility of MDR P. aeruginosa isolates (resistant to > or =3 classes of antipseudomonal agents [penicillins/cephalosporins, carbapenems, quinolones, and aminoglycosides]) obtained from a large, university-affiliated hospital. Among 235 nonrepeat bloodstream isolates screened between 2005 and 2007, 33 isolates (from 20 unique patients) were found to be MDR (crude prevalence rate, 14%). All isolates were resistant to carbapenems and quinolones, 91% were resistant to penicillins/cephalosporins, and 21% were resistant to the aminoglycosides. By using the first available isolate for each bacteremia episode (n = 18), 13 distinct clones were revealed by repetitive-element-based PCR. Western blotting revealed eight isolates (44%) to have MexB overexpression. Production of a carbapenemase (VIM-2) was found in one isolate, and mutations in gyrA (T83I) and parC (S87L) were commonly found. Growth rates of most MDR isolates were similar to that of the wild type, and two isolates (11%) were found to be hypermutable. All available isolates were susceptible to polymyxin B, and only one isolate was nonsusceptible to colistin (MIC, 3 mg/liter), but all isolates were nonsusceptible to doripenem (MIC, >2 mg/liter). Understanding and continuous monitoring of the prevalence and resistance mechanisms of MDR P. aeruginosa would enable us to formulate rational treatment strategies to combat nosocomial infections.
authors.affiliation: University of Houston College of Pharmacy, 1441 Moursund Street, Houston, 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: Kamilia
authors.initials: K
authors.lastname: Abdelraouf
authors.forename: Cristina G
authors.initials: CG
authors.lastname: Brioso
authors.forename: Magdalene
authors.initials: M
authors.lastname: Ameka
authors.forename: Laurie A
authors.initials: LA
authors.lastname: McCaskey
authors.forename: Jaye S
authors.initials: JS
authors.lastname: Weston
authors.forename: Juan-Pablo
authors.initials: JP
authors.lastname: Caeiro
authors.forename: Kevin W
authors.initials: KW
authors.lastname: Garey
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D016470:Bacteremia / Q000453:epidemiology* / Q000382:microbiology; D001426:Bacterial Proteins / Q000235:genetics; D003428:Cross Infection / Q000453:epidemiology* / Q000382:microbiology; D024901:Drug Resistance, Multiple, Bacterial; D006785:Hospitals, University; D006801:Humans; D008826:Microbial Sensitivity Tests; D015995:Prevalence; D011552:Pseudomonas Infections / Q000453:epidemiology* / Q000382:microbiology; D011550:Pseudomonas aeruginosa / Q000187:drug effects* / Q000235:genetics / Q000302:isolation & purification; D013781:Texas / Q000453:epidemiology
chemical_list: D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins