Carbapenem-resistant Pseudomonas aeruginosa: clonal spread in southern Brazil and in the state of Goiás

Abstract

This study evaluated the clonal spread of carbapenem-resistant P. aeruginosa producing SPM-1 type metallo-β-lactamase (MBL), at the university hospital of Florianópolis, Santa Catarina, Brazil, compared to an epidemic clone previously reported, as well as strains collected in other three Brazilian states. Among the isolates, 17 (62%) were clonal and highly related to strains from other regions of Brazil. Six clonal strains harbored the blaSPM-1 gene. The finding of a unique SPM-1 producer clone suggests that its dissemination has contributed to the high resistance to carbapenems in Brazilian hospitals

P. aeruginosa; carbapenem resistance; metallo- Β-lactamase

BRIEF COMMUNICATION

Carbapenem-resistant Pseudomonas aeruginosa - clonal spread in southern Brazil and in the state of Goiás

Mara Cristina Scheffer^I; Ana Cristina Gales^II; Afonso Luis Barth^III; José Rodrigues do Carmo Filho^IV; Libera Maria Dalla-Costa^V

^IServiço de Patologia Clínica do Hospital Universitário de Universidade Federal de Santa Catarina, Brazil

^IIDepartamento de Doenças Infecciosas da Universidade Federal de São Paulo, Brazil

^IIIServiço de Patologia Clínica do Hospital de Clínicas de Porto Alegre, Brazil

^IVDepartamento de Enfermagem e Departamento de Medicina da Universidade Católica de Goiás, Brazil

^VServiço de Análises Clínicas do Hospital de Clínicas da Universidade Federal do Paraná, Brazil

^VIFaculdades Pequeno Príncipe/Instituto de Pesquisa Pelé Pequeno Príncipe, Curitiba, Paraná, Brazil

^{Correspondence to}

ABSTRACT

This study evaluated the clonal spread of carbapenem-resistant P. aeruginosa producing SPM-1 type metallo-β-lactamase (MBL), at the university hospital of Florianópolis, Santa Catarina, Brazil, compared to an epidemic clone previously reported, as well as strains collected in other three Brazilian states. Among the isolates, 17 (62%) were clonal and highly related to strains from other regions of Brazil. Six clonal strains harbored the blaSPM-1 gene. The finding of a unique SPM-1 producer clone suggests that its dissemination has contributed to the high resistance to carbapenems in Brazilian hospitals.

Keywords: P. aeruginosa, carbapenem resistance, metallo-ß-lactamase

The isolation of carbapenem-resistant Pseudomonas aeruginosa is now common in Brazilian hospitals, and in some institutions this resistance rates reaches close to 50%. In 2003, Gales et al.¹ reported the spread of an epidemic clone of SPM-1-type metallo-β-lactamase (MBL) producing P. aeruginosa in hospitals located in different Brazilian states. The study analyzed strains from Bahia, Ceará, Distrito Federal, São Paulo and Paraná and found a common PFGE type among carbapenemresistant P. aeruginosa isolates from distinct geographic locations. Clonal dissemination of carbapenem-resistant P. aeruginosa was also reported in subsequent studies that included samples from other parts of the country.^2-4

Clinical isolates of carbapenem-resistant P. aeruginosa were first detected in June 2003 at the teaching hospital of the University of Santa Catarina (UFSC), Florianópolis, Santa Catarina, Brazil. The increasing frequency strains with this resistance profile have been isolated prompted us to perform this work, which aiming at evaluating the possible clonal relationship between 29 carbapenem-resistant P. aeruginosa isolates from inpatients in this hospital using macrorestriction analysis by pulsed field gel electrophoresis -PFGE [SpeI (10U), CHEF - DRIII (Bio-rad Laboratories, USA)]. The PFGE profiles were compared with those of the SP clone previously described in São Paulo¹ and were also compared with strains collected from other hospitals in Southern Brazil. Some strains from Goiás were also included. Carbapenem-resistance was measured by dilution in agar in accordance with the CLSI (M7-A7) guidelines.⁵ Polymerase chain reaction (PCR) for the bla_SPM-1 gene was performed according to Sader et al., 2005, and the PCR products were sequenced [GFX-TM PCR purification kit (Amersham Bioscience, NJ, USA), MegaBACE^TM (Amersham Bioscience, USA)].

Analysis of the genetic variability of the isolates from Florianópolis over the twoyear period from 2003 to 2005 revealed the presence of a clone (clone A) in 62% of the carbapenem-resistant P. aeruginosa. The remaining resistant isolates were unrelated to clone A according to Tenover's criteria.⁶ In addition, the present study has also shown that the clone isolated in Florianópolis (SC) is also very closely related to the isolates from Porto Alegre (RS), Curitiba (PR) and Goiânia (GO), as well as to the SP clone described by Gales et al. in 2003¹ (Figure 1).

Of the 17 isolates from Florianópolis characterized as clonal, six (35%) harbored the bla_SPM-1 gene. The MIC of these isolates was > 128 mg/L for the carbapenems tested (imipenem and meropenem). The 11 remaining clonal isolates were found to have a MIC of 32 mg/L for imipenem, while the MIC for meropenem varied from 64 mg/L to 128 mg/L, indicating the existence of other resistance mechanisms. A study using strains from hospitals in the city of Rio de Janeiro, Brazil, that were characterized as clonal by PFGE, found that SPM-1 was present in 82% of the isolates.²

MBL genes have been described as being transferable and therefore capable of disseminating independently among different species of microorganisms. However, we were only able to find SPM-1 in clonal isolates of P. aeruginosa, a finding that is similar to those reported in various studies describing the dissemination of SPM in Brazil.^1-3,7 Toleman et al. (2002) characterized the SPM-1 gene, and Poirel et al. (2004) subsequently characterized a common region called CR4 as the genetic element responsible for expression and mobilization of this gene. The latter, however, failed to transfer the putative plasmid DNA by electroporation,^3,8 suggesting that the SPM-1 gene is different from the IMP and VIM genes in terms of its ability to be transmitted among microorganisms. Our data corroborate the finding of SPM-1 only in clonal isolates of P. aeruginosa, suggesting that bla_SPM-1, which is the predominant gene in Brazil, is not as mobile as the bla_VIM or bla_IMP genes.

This study has described the first MBL-producing P. aeruginosa in Santa Catarina. Interestingly, the SPM-1 isolates from Florianópolis proved to be closely related to the Brazilian epidemic clone and strains from Porto Alegre, Curitiba and Goiânia. Therefore, one could consider that the dissemination of this clone has contributed to the high resistance to carbapenems in Brazilian hospitals, thus emphasizing the need to improve infection-control strategies.

ACKNWOLEDGEMENT

We wish to thank Dr. Ana Lúcia da Costa Darini of the Faculdade de Ciências Farmacêuticas de Ribeirão Preto/Universidade de São Paulo (FCFRP/USP), Ribeirão Preto, São Paulo, Brazil for carrying out the nucleotide sequence analysis of the amplified fragment of bla_SPM-1 found in this study.

Submitted on: 3/3/2010 A

Approved on: 8/12/2010

We declare no conflict of interest.

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Publication Dates

• Publication in this collection
  04 Jan 2011
• Date of issue
  Oct 2010

History

• Received
  03 Mar 2010
• Accepted
  12 Aug 2010