JAC Advance Access originally published online on February 6, 2007
Journal of Antimicrobial Chemotherapy 2007 59(3):576-577; doi:10.1093/jac/dkl517
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Correspondence |
Emergence of blaGES-5 in clinical colistin-only-sensitive (COS) Pseudomonas aeruginosa strain in Brazil
1 Departamento de Genética, Instituto Oswaldo Cruz, FIOCRUZ, Rio de Janeiro, Brasil 2 Departamento de Microbiologia, Instituto Nacional de Controle de Qualidade em Saúde, INCQS, FIOCRUZ, Rio de Janeiro, Brasil 3 Faculdade de Medicina, Universidade Federal do Maranhão, Brasil
* Correspondence address. Instituto Oswaldo Cruz/FIOCRUZ, Dept. Genética, Avenida Brasil 4365, PO Box 926 CEP 21045-900, Rio de Janeiro, Brasil. Tel: +00-55-21-3865-8168; Fax: +00-55-21-2260-4282; E-mail: ericafon{at}ioc.fiocruz.br
Keywords: class 1 integrons , gene cassette evolution , P. aeruginosa , Brazilian clinical setting
GES-1–9 enzymes are spread worldwide and have been found in several bacterial species conferring an extended resistance spectrum to ß-lactams.1
A nomenclature update proposed that blaGES-3 and blaGES-4 genes described by Vourli et al.2 should be renamed as blaGES-5 and blaGES-6, respectively.3 GES-5 is responsible for a decreased susceptibility to imipenem and was identified in a class 1 integron from a clinical Escherichia coli isolated in a Greek hospital2 and, more recently, in an outbreak strain of Klebsiella pneumoniae in Korea,3 and in a Pseudomonas aeruginosa isolated in China (blaGES-5 partial sequence).1
Here, we show the emergence of blaGES-5 in South America, and P. aeruginosa colistin-only-sensitive (COS) clone circulating in hospitals from the Brazilian Amazon region harbouring blaGES-1.
During 2001, P. aeruginosa isolated from nosocomial infection cases from ICU inpatients placed in the University and tertiary hospitals (15 km apart) of São Luís city, Maranhão, had their MICs of antibiotics determined using a VITEK automated system (BioMerieux, Hazelwood, MO, USA) and the Etest method (AB Biodisk, Solna, Sweden). The COS profile was attributed to isolates resistant to all anti-pseudomonal classes of antimicrobial agents, except to colistin.4
PCRs were performed using primers targeting class 1 integron signatures. The presence of metallo-ß-lactamase (MBL) genes was investigated using primers for blaIMP and blaVIM alleles, and for the blaSPM-1 gene. Integron variable regions were sequenced by the primer walking sequence strategy.
Three P. aeruginosa strains (PS1, PS26 and PS37) showed the COS profile. All isolates were resistant to cefepime, aztreonam (MIC 
32 mg/L) and ceftazidime (MIC 16– 32 mg/L). PS26 showed decreased susceptibility to imipenem (MIC 8 mg/L), while PS1 and PS37 were resistant to it (MICs of 24 mg/L and >128 mg/L, respectively).
PFGE SpeI-macrorestriction patterns revealed that PS1 and PS26, which were recovered from different hospitals, were genetically related strains (data not shown). PS37 presented a unique and discriminatory PFGE profile.
No positive result was found for MBL genes, although all strains tested positive for the presence of class 1 integron signatures. Sequencing showed that PS1 and PS26 integrons harboured a new orf followed by blaGES-1-aacA4, and PS37 carried an integron with blaGES-5-aacA4 gene cassettes (DQ236170 [GenBank] and DQ236171 [GenBank] ) (Figure 1a and 1b). All isolates presented the same integron promoter (PC), which was identical to a weak version described previously (Figure 1b),5 and was followed by an inactive P2. This weak version, as well as the hybrid one, have a promoter strength 20-fold lower than that of canonical PC.5 However, Dubois et al.6 showed a P. aeruginosa strain producing a GES-1-associated integron, despite the presence of the hybrid PC configuration. Considering these data and the resistance profile presented by the three strains, we cannot exclude the expression of the blaGES genes described here.
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The 240 bp orf, named orf126, encoded a predicted protein of 79 amino acid residues, which presented no remarkable similarity to any protein sequences available in GenBank. It seemed to be part of a gene cassette due to the presence of a 79 bp attC site (DQ236170 [GenBank] ). Interestingly, blaGES-1 from PS1 and PS26 presented the rare feature found in blaGES-1 from In52 present in a K. pneumoniae strain (Figure 1a and 1c), where an unusual attC 19 bp long was identified (AF156486 [GenBank] ).7
The blaGES-5 identified in PS37 presented a silent nucleotide change at position 54 (G 
A) when compared with the first described blaGES-5,2 and is identical to that found in K. pneumoniae from Korea,3 which has a 109 bp attC site (DQ902344
[GenBank]
). Curiously, blaGES-5 present in PS37 has the same unusual truncated attC found in the blaGES-1 from PS1, PS26 and In52 (Figure 1). Therefore, taking into account the high nucleotide identity between blaGES genes, and that each gene cassette has it own and characteristic attC, the presence of the same unusual version of attC in the blaGES-1 and blaGES-5 genes suggests that these two genes evolved recently, probably due to point mutations selected as a consequence of antibiotic pressure.
The occurrence of a blaGES-5-carrying strain presenting the COS profile imposes an immense limitation on therapy for treating P. aeruginosa infections, increasing the possibility of its persistence and spread in hospital environments.
This work showed the emergence of blaGES-5 in a P. aeruginosa strain from South America (Brazilian Amazon), probably as a consequence of point mutation events in the circulating blaGES-1, since the first description of this gene with a truncated attC was in a K. pneumoniae from French Guiana,7 a country bordering Brazilian Amazon. These results contribute to a better understanding of acquired resistance, gene cassette evolution and the dynamics of mobilization of these structures into integrons.
None to declare.
Acknowledgements
We would like to thank Anna Beatriz Robottom for the English review. This work was supported by CAPES fellowship and Oswaldo Cruz Institute grant.
References
1
Wang C, Cai P, Chang D, Mi Z. (2006) A Pseudomonas aeruginosa isolate producing the GES-5 extended-spectrum ß-lactamase. J Antimicrob Chemother 57:1261–2.
2 Vourli S, Giakkoupi P, Miriagou V, et al. (2004) Novel GES/IBC extended-spectrum ß-lactamase variants with carbapenemase activity in clinical enterobacteria. FEMS Microbiol Lett 234:209–13.[ISI][Medline]
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Jeong SH, Bae IK, Kim D, et al. (2005) First outbreak of Klebsiella pneumoniae clinical isolates producing GES-5 and SHV-12 extended-spectrum ß-lactamases in Korea. Antimicrob Agents Chemother 49:4809–10.
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6
Dubois V, Poirel L, Marie C, et al. (2002) Molecular characterization of a novel class 1 integron containing blaGES-1 and a fused product of aac(3)-Ib/aac(6'')-Ib'' gene cassettes in Pseudomonas aeruginosa. Antimicrob Agents Chemother 46:638–45.
7
Poirel L, Le Thomas I, Naas T, et al. (2000) Biochemical sequence analyses of GES-1, a novel class A extended-spectrum ß-lactamase, and the class 1 integron In52 from Klebsiella pneumoniae. Antimicrob Agents Chemother 44:622–32.
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