Characterization of Carbapenem Nonsusceptible Pseudomonas aeruginosa in Denmark: A Nationwide, Prospective Study

Abstract

From January 1st 2011 through June 30th 2011, 116 nonreplicate, noncystic fibrosis-related Pseudomonas aeruginosa isolates with reduced carbapenem susceptibility were collected from 12 out of 13 Danish departments of clinical microbiology. The presence of acquired β-lactamases was assessed with combination tablet-diffusion methodology and polymerase chain reaction. In addition, antimicrobial susceptibility testing, an efflux pump inhibitor assay, and pulsed-field gel electrophoresis (PFGE) were performed. Isolates producing acquired β-lactamases were further investigated by serotyping and multi locus sequence typing. Eight isolates produced the metallo-β-lactamase (MBL) VIM-2, and one isolate produced OXA-10 and VEB-1-like extended-spectrum beta-lactamase (ESBL). Phenotypic indications of derepressed AmpC and efflux pump were seen in 56 and 43 isolates, respectively. Overall, the results indicate that mutational factors related to permeability--often combined with derepressed, chromosomal AmpC--is the main factor behind carbapenem nonsusceptibility in Danish P. aeruginosa isolates. The ESBL producer and all the VIM producers belonged to international clones. PFGE revealed that most of the isolates were unrelated, but clonal spread was seen; the 116 isolates distributed in 97 PFGE types, with the largest cluster consisting of 4 isolates (including three isolates from the same hospital with 100% similarity). Thirty-two isolates were pair-wise related, while the remaining isolates were clonally unrelated, as were all nine ESBL/MBL producers.

Dissemination and Characteristics of a Novel Plasmid-Encoded Carbapenem-Hydrolyzing Class D β-Lactamase, OXA-436, Found in Isolates from Four Patients at Six Different Hospitals in Denmark

“…The Carba NP test was performed as previously described (34), and the OXA-48 K-SeT test (Coris BioConcept, Gembloux, Belgium) was performed according to the manufacturer's instructions. Initial PCR screening for carbapenemase-encoding genes was performed using assays previously described for the detection of bla VIM , bla IMP , bla GIM , bla SPM , bla SIM , bla NDM , bla KPC , and bla OXA-48 (3,35,36).…”

Emerging broad-spectrum resistance in Pseudomonas aeruginosa and Acinetobacter baumannii : Mechanisms and epidemiology

“…Nosocomial spread of VEB-1-producing P. aeruginosa isolates was identified in Thailand [54]. Later, other VEB-like producing isolates were reported from Kuwait and India [55,56], but also in Iran, Bulgaria, the UK and Denmark, highlighting the worldwide dissemination of these VEBproducing strains [12,[57][58][59] (Table 1). Isolates producing VEB-2 or VEB-3 were identified in Thailand and China, with these ESBLs differing from VEB-1 by only a single or two amino acid substitutions, respectively [54,60].…”

Mutation-Driven β-Lactam Resistance Mechanisms among Contemporary Ceftazidime-Nonsusceptible Pseudomonas aeruginosa Isolates from U.S. Hospitals

“…Resistance against these ␤-lactam agents in P. aeruginosa is usually multifactorial (3) and might include the derepression of the chromosomal cephalosporinase AmpC, upregulation of resistancenodulation-division (RND) efflux systems, and loss of the outer membrane channel OprD, which allows the entry of carbapenems into the cell (1)(2)(3). Furthermore, the presence of acquired ␤-lactamases, including carbapenemases, has been highlighted as a prevalent resistance mechanism against cephalosporins and carbapenems among P. aeruginosa isolates from certain geographic areas (4)(5)(6).…”