First Report of a Pseudomonas aeruginosa Isolate Coharboring KPC and VIM Carbapenemases

LETTER

Carbapenemases, such as KPC and VIM, are the most powerful β-lactamases, being able to hydrolyze nearly all β-lactams (12). Since the first identification of KPC-producing (15) and VIM-producing (16) Pseudomonas aeruginosa isolates in Colombia, their interhospital clonal dissemination throughout the country has been followed by our group. To the best of our knowledge, the copresence of VIM and KPC has not been reported in species other than Klebsiella pneumoniae (4, 8, 10, 11, 14, 17), and the only report of a P. aeruginosa isolate coharboring KPC and a metallo-β-lactamase (IMP-8) was recently published in Puerto Rico (7). Hence, we report for the first time in the world a P. aeruginosa clinical isolate that coharbors VIM and KPC.

In September 2010 in Cali, Colombia, a 49-year-old female with multiple comorbidities and end-stage renal disease had her malfunctioning peritoneal dialysis catheter surgically removed. Subsequently, she developed a carbapenem-susceptible P. aeruginosa intra-abdominal infection, which was treated with meropenem and multiple saline lavages. One month later, she was taken to surgery to receive a renal transplant, but an intra-abdominal infection was evidenced. The transplant was postponed, and the patient was restarted on meropenem and lavages. A panresistant P. aeruginosa isolate (3386) was obtained from one of the lavages; there had been no previous exposure to polymyxin. Since the patient was showing clinical improvement, meropenem was continued as monotherapy with an adequate outcome. The patient was discharged, and screening cultures performed 5 months later did not show evidence of colonization by carbapenem-resistant P. aeruginosa.

Isolate 3386 was sent to CIDEIM, where the species was reidentified using Vitek2 (bioMérieux, Mercy l'Etoile, France), and antibiotic susceptibility testing was performed by the broth microdilution method (Sensititre panels; TREK Diagnostic Systems, Westlake, OH). According to CLSI breakpoints (2), the isolate was resistant to amikacin, ciprofloxacin, polymyxin (MIC, >32 μg/ml), and all β-lactams, including carbapenems (MIC, >64 μg/ml) and aztreonam. PCR-based screening for bla_CTX-M, bla_TEM, bla_SHV, bla_IMP, bla_KPC, and bla_VIM gave positive results for these last two genes, which were identified as bla_KPC-2 and bla_VIM-2 by sequencing.

S1 nuclease/I-CeuI digestions and probe hybridizations (1, 6) revealed that bla_KPC was chromosomal while bla_VIM was located chromosomally as well as in a large plasmid (280 kb). PCR mapping to study the genetic environment of bla_KPC-2 (3) and bla_VIM-2 (5, 9) revealed that bla_KPC-2 was located on Tn4401b while bla_VIM-2 was part of a class 1 integron, preceded by aacA29a and followed by aacA29b and qacEΔ1sulf-1 cassettes, as previously reported (3, 13). Multilocus sequence typing (MLST) performed according to the P. aeruginosa MLST website (http://pubmlst.org/paeruginosa/) showed that the isolate belonged to the sequence type (ST) ST111, which has been associated with the international spread of metallo-β-lactamases (13). According to pulsed-field gel electrophoresis (PFGE), this isolate was confirmed to be part of a successful VIM-2-harboring clone that has been circulating in two Colombian cities since 2007.

The copresence of bla_VIM and bla_KPC in a P. aeruginosa isolate has never been encountered until now. Given the panresistant phenotype observed and its association with the international successful clone P. aeruginosa ST111, our findings represent a major threat to public health considering the possibility of global dissemination.