MEM INST OSWALDO CRUZ, RIO DE JANEIRO, 111(9) September 2016
PAGES: 597-598 DOI: 10.1590/0074-02760160188 Letter to the editor
Emergence of Acinetobacter baumannii ST730 carrying the blaOXA-72 gene in Brazil

Mariana Pagano1,2,+, Franciéli P Rozales1,2, Diego Bertolini2, Lisiane Rocha3, Jorge LM Sampaio3, Afonso L Barth1,2, Andreza F Martins2,4

1Universidade Federal do Rio Grande do Sul, Faculdade de Farmácia, Programa de Pós-Graduação em Ciências Farmacêuticas, Porto Alegre, RS, Brasil
2Hospital de Clínicas de Porto Alegre, Centro de Pesquisa Experimental, Laboratório de Pesquisa em Resistência Bacteriana, Porto Alegre, RS, Brasil
3Laboratório Fleury, Porto Alegre, RS, Brasil
4Universidade Federal do Rio Grande do Sul, Programa de Pós-Graduação em Microbiologia Agrícola e do Ambiente, Porto Alegre, RS, Brasil

Abstract

Over the last decade, Acinetobacter baumannii resistant to carbapenems has emerged in many medical centres and has been commonly associated with high morbimortality. In Brazil, this resistance is mainly attributed to the spread of OXA-23-producing clones and, to a lesser extent, to OXA-143-producing clones. Here, we describe, for the first time, two OXA-72-producing A. baumannii isolates in southern Brazil to a broad spectrum of antibiotics, except polymyxin B and tigecycline. Molecular typing by multilocus sequence typing (MLST) demonstrated that both OXA-72-producing isolates belong to a new sequence type (ST), ST730, which was recently identified in OXA-23-producing A. baumannii isolates in São Paulo, Brazil. We demonstrate that the two A. baumannii ST730 isolates carrying blaOXA-72 share a common ancestral origin with the blaOXA-23 producers in Brazil. This observation reinforces the importance of strain-typing methods in order to clarify the dynamics of the emergence of new clones in a geographic region.

Recently, a new sequence type, ST730, from an OXA-23-producing Acinetobacter baumannii has been deposited in the multilocus sequence typing (MLST) database (http://www.pasteur.fr) (Vasconcelos et al. 2015). In the present study, we describe two isolates of A. baumannii ST730 carrying the blaOXA-72 gene from different patients in a hospital located in southern Brazil.

In March 2013, a carbapenem-resistant Acinetobacter sp. was isolated using VITEK®2 system (bioMérieux, La Balme-les-Grottes, France) from the tracheal aspirate (> 106 CFU/mL) of a 76-year-old female ICU patient in a 312-bed tertiary care hospital in Porto Alegre, southern Brazil. A few days later, another carbapenem-resistance in Acinetobacter sp. was reported from a blood culture (positive in 12 h) of an 86-year-old male ICU patient admitted with sepsis in the same hospital. Both the isolates were identified as A. baumannii by matrix-assisted laser desorption/ionisation time-of-flight (MALDI-TOF; Bruker Daltonik, Bremen, Germany) spectrometry and gyrB multiplex polymerase chain reaction (PCR). Disc-diffusion assays demonstrated that the isolates were resistant to meropenem, imipenem, amikacin, ampicillin-sulbactam, cefepime and ceftazidime. However, the isolates were found to be susceptible to polymyxin (MICs 1 and 2 µg/mL) and tigecycline (MICs 0.5 and 0.75 µg/mL) as per microdilution and Etest® assays, respectively. The results obtained were interpreted according to the CLSI guidelines (CLSI 2014). The carbapenemase genes (blaOXA-23-like, blaOXA-24/40-like, blaOXA-58-like and blaOXA-143-like) were investigated by multiplex PCR as previously described (Higgins et al. 2010). The blaOXA-24/40-like gene was detected in both the isolates. Sequencing of blaOXA-24 gene (ABI 3500 Genetic Analyzer; Applied Biosystems, Foster City, CA, United States) identified the variant blaOXA-72, which displayed 100% identity to the original blaOXA-72 gene (GenBank accession number AY739646.1). Clonal diversity, investigated by repetitive-sequence-based PCR (REP-PCR), revealed an identical profile of the isolates (Bou et al. 2000). MLST was performed according to the Institut Pasteur scheme (http://www.pasteur.fr) and both the isolates were identified as ST730.

Resistance to carbapenems among A. baumannii isolates from Brazil has been mostly related to the production of OXA-23, followed by OXA-143 (Vasconcelos et al. 2015). In fact, OXA-72-producing A. baumannii isolates are still uncommon in Brazil. The first two cases of A. baumannii carrying blaOXA-72 gene were reported from São Paulo (Southeast Brazil) in 2011 (Antonio et al. 2011, Werneck et al. 2011). Two years later, this gene was reported in two other A. baumannii isolates from Recife (Northeast Brazil) (Cavalcanti et al. 2013). Recently, a surveillance study evaluated nine hospitals from five different states, representative of all the Brazilian regions, and described an inter-hospital dissemination of 10 A. baumannii isolates containing blaOXA-72 in São Paulo (Vasconcelos et al. 2015). These data highlight the possibility of the spread of this gene in the country. Furthermore (Werneck et al. 2011), reported the presence of blaOXA-72 gene inserted on a plasmid of ~ 86 kb, highlighting its potential for spread.

Here, we describe, for the first time, two A. baumannii isolates harbouring the blaOXA-72 gene isolated from Rio Grande do Sul, southern Brazil. These data point towards the increasing diversity of oxacillinases among the clinical isolates of Acinetobacter spp. in Brazil. Recently, Cayô et al. (2015) deposited an OXA-23-producing isolate, A. baumannii ST730, in the Institut Pasteur database. ST730 is a single-locus variation of ST79 (CC79), responsible for the spread of blaOXA-23 in Latin America (Chagas et al. 2014, Vasconcelos et al. 2015). It is worrisome that the emergent OXA-72-producing clones share the same phylogenetic origin with the clones harbouring blaOXA-23 gene, since the latter demonstrated a remarkable capacity of dissemination and maintenance along the years in Brazilian hospitals (Pagano et al. 2015). The results presented in this study highlight the importance of monitoring the spread of successful clones associated with the dissemination of A. baumannii carrying blaOXA in Brazil by molecular epidemiology methods such as MLST.

 

REFERENCES

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Vasconcelos AT, Barth AL, Zavascki AP, Gales AC, Levin AS, Lucaravschi BR, et al. The changing epidemiology of Acinetobacter spp. producing OXA carbapenemases causing bloodstream infections in Brazil: a BrasNet report. Diagn Microbiol Infect Dis. 2015; 83(4): 382-5.

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Received 2 May 2016
Accepted 27 June 2016

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