title: Alterations of OprD in carbapenem-intermediate and -susceptible strains of Pseudomonas aeruginosa isolated from patients with bacteremia in a Spanish multicenter study.
abstract: We investigated the presence of OprD mutations in 60 strains of metallo-ß-lactamase-negative Pseudomonas aeruginosa intermediately susceptible (IS [n = 12]; MIC = 8 μg/ml) or susceptible (S [n = 48]; MICs ≤ 1 to 4 μg/ml) to imipenem and/or meropenem that were isolated from patients with bacteremia in order to evaluate their impact on carbapenem susceptibility profiles. The presence of mutations in oprD was detected by sequencing analysis. OprD expression was assessed by both outer membrane protein (OMP) analysis and real-time PCR (RT-PCR). Fourteen (23%) isolates had an OprD identical to that of PAO1, and OprD modifications were detected in 46 isolates (77%). Isolates were classified as OprD "full-length types" (T1 [n = 40, including both wild-type OprD and variants showing several polymorphisms]) and OprD "deficient types" (T2 [n = 3 for OprD frameshift mutations] and T3 [n = 17 for premature stop codons in oprD]). RT-PCR showed that 5 OprD type T1 isolates presented reduced transcription of oprD (0.1- to 0.4-fold compared to PAO1), while oprD levels increased more than 2-fold over that seen with PAO1 in 4 OprD type T1 isolates. A total of 50% of the isolates belonging to OprD "deficient types" were susceptible to both carbapenems, and 40% were susceptible to meropenem and intermediately susceptible to imipenem. Only one isolate (5%) within this group was intermediately susceptible to both carbapenems, and one (5%) was susceptible to imipenem and intermediately susceptible to meropenem. We concluded that OprD inactivating mutations in clinical isolates of P. aeruginosa are not restricted only to carbapenem-resistant isolates but are also found in isolates with imipenem or meropenem MICs of only 0.06 to 4 μg/ml.
authors.affiliation: Hospital Universitario Marqués de Valdecilla-IFIMAV, Santander, Spain. aocampo@humv.es
authors.forename: Alain A
authors.initials: AA
authors.lastname: Ocampo-Sosa
authors.forename: Gabriel
authors.initials: G
authors.lastname: Cabot
authors.forename: Cristina
authors.initials: C
authors.lastname: Rodríguez
authors.forename: Elena
authors.initials: E
authors.lastname: Roman
authors.forename: Fe
authors.initials: F
authors.lastname: Tubau
authors.forename: María D
authors.initials: MD
authors.lastname: Macia
authors.forename: Bartolomé
authors.initials: B
authors.lastname: Moya
authors.forename: Laura
authors.initials: L
authors.lastname: Zamorano
authors.forename: Cristina
authors.initials: C
authors.lastname: Suárez
authors.forename: Carmen
authors.initials: C
authors.lastname: Peña
authors.forename: María A
authors.initials: MA
authors.lastname: Domínguez
authors.forename: Gabriel
authors.initials: G
authors.lastname: Moncalián
authors.forename: Antonio
authors.initials: A
authors.lastname: Oliver
authors.forename: Luis
authors.initials: L
authors.lastname: Martínez-Martínez
mesh_terms: D000595:Amino Acid Sequence; D016470:Bacteremia / Q000382:microbiology*; D001426:Bacterial Proteins / Q000096:biosynthesis / Q000235:genetics; D015780:Carbapenems / Q000494:pharmacology*; D004269:DNA, Bacterial / Q000235:genetics; D024881:Drug Resistance, Bacterial / Q000235:genetics*; D016521:Electrophoresis, Gel, Pulsed-Field; D015964:Gene Expression Regulation, Bacterial / Q000235:genetics; D006868:Hydrolysis; D008826:Microbial Sensitivity Tests; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009154:Mutation / Q000235:genetics / Q000502:physiology; D018272:Porins / Q000235:genetics*; D011487:Protein Conformation; D011552:Pseudomonas Infections / Q000382:microbiology*; D011550:Pseudomonas aeruginosa / Q000187:drug effects* / Q000235:genetics*; D060888:Real-Time Polymerase Chain Reaction; D013030:Spain; D001618:beta-Lactamases / Q000096:biosynthesis / Q000235:genetics
chemical_list: D001426:Bacterial Proteins; D015780:Carbapenems; D004269:DNA, Bacterial; D018272:Porins; C077157:OprD protein, Pseudomonas aeruginosa; C048795:AmpC beta-lactamases; D001618:beta-Lactamases