JAC Advance Access originally published online on January 31, 2008
Journal of Antimicrobial Chemotherapy 2008 61(3):749-751; doi:10.1093/jac/dkm529
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Research letters |
Nosocomial infections caused by multidrug-resistant Pseudomonas putida isolates producing VIM-2 and VIM-4 metallo-β-lactamases
1 Laboratoire de Bactériologie, Université catholique de Louvain, Cliniques Universitaires UCL de Mont-Godinne, B-5530 Yvoir, Belgium 2 Service de Microbiologie, Hôpital Erasme-ULB, Université Libre de Bruxelles, B-1070 Brussels, Belgium
* Corresponding author. E-mail: pierre.bogaerts{at}uclouvain.be
Keywords: carbapenems , MBLs , ESBLs , P. putida , β-lactams
Nosocomial infections caused by multidrug-resistant and carbapenem-resistant Pseudomonas putida isolates have been occasionally reported in severely ill or immunocompromised patients hospitalized in the intensive care unit (ICU).1 Here, we report briefly the microbiological characteristics of several carbapenem-resistant P. putida isolates producing VIM metallo-β-lactamases (MBLs) at two Belgian university hospitals located in the Brussels area.
Between January 2004 and May 2007, multidrug-resistant P. putida strains originating from 10 inpatients hospitalized at Saint-Luc (hospital 1) and Erasme (hospital 2) university hospitals were characterized for resistance mechanisms to β-lactams. All the isolates were high-level resistant to imipenem and meropenem by disc diffusion testing (no inhibition zone). The 10 patients presented with severe underlying diseases (Table 1) had been hospitalized more than 9 days in ICUs and had all previously received broad-spectrum antimicrobial therapy. All but one of the isolates had been recovered from urine specimens. Bacterial identification to the species level was achieved with Vitek2-GN (bioMérieux) and control growth at 42°C on trypticase soy agar complemented with sheep blood. MICs determined by Etest (AB Biodisk) showed that all isolates were resistant to piperacillin/tazobactam, ceftazidime, aztreonam, imipenem and meropenem and all but one were resistant to cefepime (Table 1). Isolates recovered from hospital 1 were resistant to amikacin, whereas isolates from hospital 2 remained susceptible to this aminoglycoside. Resistance to ciprofloxacin was variable but all isolates remained susceptible to colistin. The MBL screening test was positive both by double-disc method (imipenem versus imipenem-EDTA; Rosco Diagnostica A/S) and by MBL double-sided Etest (imipenem/imipenem-EDTA; AB Biodisk) for all isolates (data not shown). PCR targeting blaIMP (FW, 5'-GGC GTT TAT GTT CAT ACT TCG TT; RV, 5'-TCG AGA ATT AAG CCA CTC TAT TCC), blaVIM (FW, 5'-TGT CCG TGA TGG TGA TGA GT; RV, 5'-ATT CAG CCA GAT CGG CAT C), various ESBL genes (blaTEM, blaVEB, blaPER, blaGES, blaBEL-1, blaOXA of Groups 1, 2 and 3, blaOXA-20, blaOXA-18), and penicillinase genes (blaCARB5: FW, 5'-TGG AAA CGG GAA AAC GTT GG; RV, 5'-CAC GCG ACC CAT AAC CAC CA; blaCARB 1 to 4 and 6: FW, 5'-GGA TTA CAA TGG CAA TCA GC; RV, 5'-TGT CGT ATC CCT CAA ATC ACC) was only positive for the blaVIM gene in all 10 isolates and for the blaPER gene in a single isolate (no. 6). Sequencing of the variable region of class I integrons obtained for the different strains revealed two distinct integrons. The first one, isolated from all five isolates from hospital 1, harboured an aacA4 allele coding for the AAC(6')-Ib aminoglycoside-modifying enzyme explaining the resistance to amikacin, followed by the blaVIM-4 gene. The same integron has already been identified in Pseudomonas aeruginosa isolates reported from Poland and Hungary2,3 and presents a specific 170 bp 3'-terminal repeat of the blaVIM-4 gene. The second class I integron, obtained from the five strains isolated in hospital 2, revealed a blaVIM-2 gene cassette, following an unidentified open reading frame of 318 nucleotides named orfukn. This last sequence is referenced in GenBank under number EU284133. PCR sequencing confirmed that the blaPER gene detected in isolate no. 6 was a blaPER-1 allele. The co-presence of blaPER and blaVIM-2 has been reported in P. aeruginosa4,5 and Providencia,6 but to the best of our knowledge, this is the first description in P. putida. PFGE analysis revealed five PFGE types among the 10 P. putida isolates. Types A and B were recovered from hospital 1, whereas types C, D and E were found in hospital 2. A cluster of four patients showing PFGE type B was found in hospital 1 and another cluster of three patients with PFGE type C was present in hospital 2. Further, the content of the gene cassettes of the P. putida strains also clearly differed between the two centres excluding the possibility of strain transfer or horizontal gene transfer between the two hospitals. The data, instead, suggest that clonal dissemination of P. putida strains as well as horizontal blaVIM-2 and blaVIM-4 gene transfer through different clones independently occurred at both centres. Indeed, the same variable sequence of integron was found in isolates with different PFGE types in one centre. The fact that geographical and time clustering of these multidrug-resistant P. putida isolates were recorded in both centres also sustains the hypotheses of either patient-to-patient cross-transfer of strains or a common source acquisition. Although no epidemiological investigations were performed, it is striking that nearly all P. putida isolates originated from urine obtained from patients with bladder catheters, four of whom had undergone invasive urinary tract examinations. In some cases, long periods (e.g. isolate nos 5 and 7) elapsed between the isolation of genotypically similar resistant P. putida strains from ICU patients. This observation raises the possibility that these strains may have persisted unnoticed in the ICU environment, which served as a source of patient contamination.
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Among the 10 patients, 5 recovered clinically and 5 died. No direct link could be established between the isolation of P. putida and death in any of these patients. The P. putida isolates were considered as colonizing organisms in eight patients (none of whom received any specific antimicrobial therapy) and as clinically significant in the remaining two patients. The latter two patients received intravenous colistin therapy and were considered as cured from their urinary tract infection following this treatment.
Overall, our data document the emergence of multidrug-resistant P. putida isolates producing VIM-2 and VIM-4 MBLs, presumably arising by independent horizontal transfer of integron-associated resistance genes into distinct epidemic P. putida clones in two hospitals. This observation also underscores that P. putida, although infrequently isolated, may occasionally cause difficult-to-treat nosocomial infections in severely ill patients.
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This work was partially funded by a grant from the Belgian Antibiotic Policy Coordination Committee (BAPCOC) of the Belgian Ministry for Public Health.
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None to declare.
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1 Almuzara M, Radice M, de Garate N, et al. VIM-2-producing Pseudomonas putida, Buenos Aires. Emerg Infect Dis (2007) 13:668–9.[Web of Science][Medline]
2
Patzer J, Toleman M, Deshpande L, et al. Pseudomonas aeruginosa strains harbouring an unusual blaVIM-4 gene cassette isolated from hospitalized children in Poland (1998–2001). J Antimicrob Chemother (2004) 53:451–6.
3
Libisch B, Gacs M, Csiszar K, et al. Isolation of an integron-borne blaVIM-4 type metallo-β-lactamase gene from a carbapenem-resistant Pseudomonas aeruginosa clinical isolate in Hungary. Antimicrob Agents Chemother (2004) 48:3576–8.
4
Yakupogullari Y, Poirel L, Bernabeu S, et al. Multidrug-resistant Pseudomonas aeruginosa isolate co-expressing extended-spectrum β-lactamase PER-1 and metallo-β-lactamase VIM-2 from Turkey. J Antimicrob Chemother (2008) 61:221–2.
5 Docquier JD, Luzzaro F, Amicosante G, et al. Multidrug-resistant Pseudomonas aeruginosa producing PER-1 extended-spectrum serine-β-lactamase and VIM-2 metallo-β-lactamase. Emerg Infect Dis (2001) 7:910–1.[Web of Science][Medline]
6 Lee H-W, Kang H-Y, Shin K-S, et al. Multidrug-resistant Providencia isolates carrying blaPER-1, blaVIM-2 and armA. J Microbiol (2007) 45:272–4.[Web of Science][Medline]
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