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Antimicrobial Agents and Chemotherapy, January 2005, p. 474-475, Vol. 49, No. 1
0066-4804/05/$08.00+0 doi:10.1128/AAC.49.1.474-475.2005
Copyright © 2005, American Society for Microbiology. All Rights Reserved.
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In November 2002, after 8 days of meropenem treatment (120 mg/kg of body weight/day), P. aeruginosa M5109 was recovered as the sole isolate from the catheter of a 7-month-old patient at the Hospital de Niños "Ricardo Gutierrez." The isolate was confirmed to be P. aeruginosa by using the API20NE system (bioMérieux, Marcy l'Etoile, France) and displayed uncommonly high levels of carbapenem resistance and synergism between imipenem- and zinc chelator-containing disks. Based on the antibiotype profile, colistin was added to the meropenem treatment, and the patient was discharged alive.
By susceptibility analysis carried out by agar dilution according to NCCLS guidelines (6), M5109 showed resistance to ticarcillin (MIC, 1,024 µg/ml), piperacillin (MIC, >1,024 µg/ml), piperacillin-tazobactam (MIC, 512 µg/ml), cefotaxime (MIC, 512 µg/ml), ceftazidime (MIC, 256 µg/ml), cefepime (MIC, 64 µg/ml), aztreonam (MIC, 32 µg/ml), imipenem (MIC, 512 µg/ml), meropenem (MIC, 128 µg/ml), amikacin (MIC, 256 µg/ml), gentamicin (MIC, >512 µg/ml), and ciprofloxacin (MIC, 32 µg/ml) but not to colistin (MIC, 0.5 µg/ml). The addition of 0.4 mM EDTA produced a
32-fold decrease in the carbapenem MICs. A carbapenemase was detected by a microbiological assay (4). Attempts to transfer ceftazidime or imipenem resistance by biparental conjugation (4) to P. aeruginosa ATCC 27853 were unsuccessful.
PCR screening of bla genes followed by DNA sequencing revealed the presence of blaTEM-1-like (6), blaOXA-2-like (1), blaGES-1-like (primers used were GES-F [5'-GAAAAAGCAGCTCAGATCG] and GES-R [5'-CAACAACCCAATCTTTAGGA]), and blaVIM-2-like (primers used were VIM-F and VIM-R [5]) (amplicons of 500, 480, 580, and 261 bp, respectively). Amplification for other ESBL (blaCTX-M-2, blaPER, and blaSHV [4]) or MBL (blaSPM-1 and blaIMP [unpublished data]) genes was negative. Since all the blaVIM genes and most of the blaGES genes presently reported are integron located (7, 9), we performed PCRs combining the primer 5'-CS, directed against the 5'-conserved segment of class 1 integrons (4), with either VIM-R or GES-R, rendering amplicons of 475 and 819 bp, respectively. Thus, both blaVIM-2-like and blaGES-1-like were found as the first cassettes of different class 1 integrons in M5109. For further sequencing of these genes, additional reverse primers (VIM-Rb [5'-TGTTATGCCGCATCTGCCTG] and GES-Rc [5'-TCAACTATTTGTCCGTGCTC], respectively) were designed based on sequence alignments of highly related genes (Clustal X; ftp://ftp-igbmc.u-strasbg.fr/pub/). The 5'-CS-VIM-Rb amplicon (948 bp) contained an 801-bp-long open reading frame carrying the new blaVIM-11 allele, which differs from blaVIM-2 in a unique, nonsynonymous mutation and from blaVIM-3 or blaVIM-6 in another nonsilent change. Therefore, it may be considered an evolutionary intermediate between blaVIM-2 and blaVIM-3/6 (Fig. 1). The 1,008-bp-long 5'-CS-GES-Rc amplicon harbored an open reading frame of 864 bp that showed a unique silent change (C
T) at nucleotide position 591 relative to the blaGES-1 sequence.
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FIG. 1. Relatedness of blaVIM genes. (A) Neighbor-joining tree of all the following blaVIM genes reported to date (with GenBank accession numbers given in parentheses): blaVIM-1 (Y18050), blaVIM-2 (AF191564), blaVIM-3 (AF300454), blaVIM-4 (AY135661), blaVIM-5 (AY144612), blaVIM-6 (AY165025), blaVIM-7 (AJ536835), blaVIM-8 (AY524987), blaVIM-9 (AY524988), blaVIM-10 (AY524989), and blaVIM-11 (AY605049). (B) Substitutions in genes highly related to blaVIM-2. The nucleotide positions of the indicated mutations (relative to the blaVIM-2 sequence) are shown. Amino acid changes and their positions based on the numbering system described by Galleni et al. (2) are indicated in parentheses.
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This is the first report of an MBL-mediated carbapenem-resistant and ESBL-producing P. aeruginosa isolate in Argentina and the first description anywhere of the coexistence of a VIM variant with GES-1 in a single strain. Our results, together with previous findings (M. Castanheira, R. E. Mendes, T. R. Walsh, A. C. Gales, and R. N. Jones, Letter, Antimicrob. Agents Chemother. 48:2344-2345, 2004; R. E. Mendes et al., letter, 2004), indicate that both VIM- and GES-producing P. aeruginosa strains have already become established in Latin America. The emergence of these enzymes in P. aeruginosa constitutes a public health concern in Argentina which requires efficient detection and brisk intervention to preserve antibiotic options.
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Fernando Pasteran Diego Faccone Alejandro Petroni Melina Rapoport Marcelo Galas* Servicio Antimicrobianos Departamento Bacteriología Instituto Nacional de Enfermedades Infecciosas-ANLIS "Dr. Carlos G. Malbrán" Ciudad Autónoma de Buenos Aires, Argentina
Miryam Vázquez
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| * Phone and fax: 54 11 4 303 2812,E-mail: mgalas{at}anlis.gov.ar |
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