Characterization of carbapenem-resistant Pseudomonas aeruginosa clinical isolates, carrying multiple genes coding for this antibiotic resistance

Abstract

BackgroundCarbapenemase genes are one of the most frequent mechanisms reported in carbapenem-resistant P. aeruginosa; however, description of P. aeruginosa co-harbouring two or more carbapenemases is unusual.MethodsIn this study we evaluated the presence of carbapenemase genes and the clonality of P. aeruginosa isolates obtained from a hospital over a 12-year period. A total of 127 isolates of carbapenem-resistant P. aeruginosa recovered from 109 patients feces (four samples), rectal swab (three samples), nasal swab (one sample) and anal abscess (one sample), were evaluated. Minimum inhibitory concentrations of the following antibiotics imipenem, meropenem and polymyxin E were determined by broth microdilution. The molecular profile of isolates was evaluated by pulsed field gel electrophoresis (PFGE). PCR for the following carbapenemase genes blaIMP;blaSPM;blaVIM;blaSIM;blaNDM;blaKPC;blaGES and nucleotide sequencing to confirm the enzyme gene types were performed and compared with the database available on the Internet (BLAST-http://www.ncbi.nlm.nhi.gov/blast/).ResultsAll isolates were carbapenem-resistant, their MIC50 and MIC90 were respectively 64 μg/mL and 256 μg/mL to imipenem and 32 μg/mL and 256 μg/mL to meropenem, all isolates except one (MIC = 8 mg/L) were susceptible to polymyxin E. The most frequent carbapenemase genes identified were blaSPM identified in 41 isolates (32%), followed by 10 with blakpc and 5 with blaVIM (3.9%). All belonged to the class SPM-1 and VIM-2. In 2011, one isolate harbouring three carbapenemase genes (SPM-1, VIM-2 and KPC-2) that belonged to a new clone was identified in a hematopoietic stem cell transplanted patient. Then, 19 carbapenem-resistant P. aeruginosa were identified in an outbreak that occurred in the bone marrow transplant unit, all positive for SPM-1 gene, and 9 (47.3%) harbored both SPM-1 and KPC.ConclusionOur findings showed that PCR for KPC gene should be performed to evaluate carbapenem resistance in P. aeruginosa and that this agent can harbor more than one carbapenemase gene. Attention should be focused on the possible rapid spread of KPC in P. aeruginosa isolates and for the fact that P. aeruginosa may become a reservoir of this transmissible resistance mechanism.

Molecular characterization of resistance mechanisms in Pseudomonas aeruginosa isolates resistant to carbapenems

“…Also, we detected P. aeruginosa isolates with more than one carbapenemase gene, of which four of them possessed three genes; blaNDM-1, blaVIM-1 and blaVIM-2. Few studies have reported the coexistence of carbapenemases encoding genes in the same P. aeruginosa isolate such as KPC and IMP-8 in Puerto Rico [37], KPC and VIM in Colombia [38] and SPM-1, KPC-2 and VIM-2 in Brazil [39].…”

New Small Plasmid Harboring bla KPC-2 in Pseudomonas aeruginosa

“…First reported in Colombia in 2006 (4), subsequent worldwide reports described plasmid and chromosomal genetic contexts for this gene. In Brazil, KPC-producing P. aeruginosa was first described in 2012 (5), followed by a second report (6) that highlighted a worrying increase in KPC-producing P. aeruginosa. However, the genetic context of bla KPC in the Brazilian strains remained unknown.…”

β-lactamase-producing Gram-negative bacteria in an intensive care unit in southern Brazil

“…The predominant carbapenemases include New Delhi metallo-β-lactamases (NDM), Oxacillinases (OXA), Verona integron-encoded metallo-β-lactamase (VIM), Imipenemase (IMP), and KPC, which are encoded by the genes bla NDM , bla OXA , bla VIM , bla IMP , and bla KPC , respectively (Nordman, Naas, Poirel, 2011). In Brazil, some types of carbapenemases have been detected more frequently, such as São Paulo metallo-β-lactamase (SPM) in P. aeruginosa isolates (Rossi, 2011;Rizek et al, 2014. ), OXA-23 in Acinetobacter spp.…”