title: Nosocomial outbreak of a non-cefepime-susceptible ceftazidime-susceptible Pseudomonas aeruginosa strain overexpressing MexXY-OprM and producing an integron-borne PSE-1 betta-lactamase.
abstract: Cefepime (FEP) and ceftazidime (CAZ) are broad-spectrum cephalosporins that display similar MICs for wild-type Pseudomonas aeruginosa strains. Recently, P. aeruginosa isolates showing a discordance in susceptibility to CAZ and FEP have been noted at the Hospital de Bellvitge in Barcelona, Spain, and a clustering was suspected. During the study period (March to December 2007), 51 patients, particularly those in an intensive care units (ICUs) (n = 29 [57%]), infected or colonized with at least one P. aeruginosa non-FEP-susceptible and CAZ-susceptible (Fep(ns) Caz(s)) phenotype strain were detected. Twenty-three (45%) patients were infected, and the respiratory tract was the most frequent site of infection. Changes in the consumption of antimicrobials in the ICUs were observed over time: a progressive reduction in the levels of consumption of carbapenems (247 defined daily doses [DDD]/1,000 patient days to 66 DDD/1,000 patient days; P = 0.008), after restriction of its use in 2006, and an expected increase in the rate of piperacillin-tazobactam use (42 DDD/1,000 patient days in 2004 to 200 DDD/1,000 patient days in 2007; P < 0.001). Throughout the whole study period, only a single clone of a P. aeruginosa Fep(ns) Caz(s) phenotype strain was identified by pulsed-field gel electrophoresis analysis to be associated with the hyperexpression of MexXY-OprM and the production of an integron-borne PSE-1 ss-lactamase. In conclusion, we identified an epidemic P. aeruginosa clone of an Fep(ns) Caz(s) phenotype strain involving 51 patients, in particular, ICU patients. The combination of the overexpression of an efflux pump and PSE-1 ss-lactamase production is associated with the multidrug-resistant phenotype. The dominant use of a single class of antibiotics could have provided the selective pressure required for the emergence and spread of this P. aeruginosa strain.
authors.affiliation: Hospital de Bellvitge, Barcelona, Spain. cpena@csub.scs.es
authors.forename: C
authors.initials: C
authors.lastname: Peña
authors.forename: C
authors.initials: C
authors.lastname: Suarez
authors.forename: F
authors.initials: F
authors.lastname: Tubau
authors.forename: C
authors.initials: C
authors.lastname: Juan
authors.forename: B
authors.initials: B
authors.lastname: Moya
authors.forename: M A
authors.initials: MA
authors.lastname: Dominguez
authors.forename: A
authors.initials: A
authors.lastname: Oliver
authors.forename: M
authors.initials: M
authors.lastname: Pujol
authors.forename: J
authors.initials: J
authors.lastname: Ariza
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001425:Bacterial Outer Membrane Proteins / Q000096:biosynthesis* / Q000235:genetics; D001426:Bacterial Proteins / Q000096:biosynthesis* / Q000235:genetics; D000077723:Cefepime; D002442:Ceftazidime / Q000494:pharmacology; D002511:Cephalosporins / Q000494:pharmacology; D003428:Cross Infection / Q000453:epidemiology* / Q000382:microbiology; D004196:Disease Outbreaks; D024901:Drug Resistance, Multiple, Bacterial; D004363:Drug Utilization / Q000706:statistics & numerical data; D005260:Female; D015870:Gene Expression; D005798:Genes, Bacterial; D006761:Hospitals; D006801:Humans; D032023:Integrons; D007362:Intensive Care Units; D008297:Male; D026901:Membrane Transport Proteins / Q000096:biosynthesis* / Q000235:genetics; D008875:Middle Aged; D011552:Pseudomonas Infections / Q000453:epidemiology* / Q000382:microbiology; D011550:Pseudomonas aeruginosa / Q000187:drug effects*; D012137:Respiratory System / Q000382:microbiology; D013030:Spain / Q000453:epidemiology
chemical_list: D000900:Anti-Bacterial Agents; D001425:Bacterial Outer Membrane Proteins; D001426:Bacterial Proteins; D002511:Cephalosporins; D026901:Membrane Transport Proteins; C402791:MexXY protein, Pseudomonas aeruginosa; C402263:OprM protein, Pseudomonas aeruginosa; D000077723:Cefepime; D002442:Ceftazidime