AAC Accepts, published online ahead of print on 27 October 2014 Antimicrob. Agents Chemother. doi:10.1128/AAC.02415-14 Copyright © 2014, American Society for Microbiology. All Rights Reserved.
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Antimicrobial Agents and Chemotherapy, Short-form
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Association of Class 1 and 2 integrons with multidrug-resistant (MDR)
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Acinetobacter baumannii international clones and Acinetobacter nosocomialis isolates
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Running title: Integrons in A. baumannii and A. nosocomialis
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Natacha Martins1, Renata Cristina Picão1, Sheila Adams-Sapper2, Lee W. Riley2 and
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Beatriz Meurer Moreira1*
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Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil, 2School of Public
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Health, University of California, Berkeley, CA, USA.
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*Corresponding author. Beatriz M Moreira, MD PhD, Centro de Ciências da Saúde,
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Bloco I. Av. Carlos Chagas Filho 373. Postal code 21941-902, Cidade Universitária, RJ,
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Brazil. Phone: +5521-25608344. Fax: +5521-25608344. Email:
[email protected]
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Abstract (75 words)
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Acinetobacter baumannii clonal complex (CC) 113/79 and class 2 integrons predominate
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in Latin America; a relationship between these characteristics was explored. Presence of
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integrases was determined in successive hospital Acinetobacter isolates (163 A.
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baumannii and 72 A. nosocomialis). Most had integrons, but class 1 and 2 were
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significantly more frequent in CC109/1 and CC113/79, respectively. Class 2 integron
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predominance in Latin America may be accounted for the high prevalence of CC113/79.
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Keywords:
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Acinetobacter nosocomialis
Integrons,
MLST,
international
clones,
Acinetobacter
baumannii,
2
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The dissemination of multidrug-resistant (MDR) Acinetobacter baumannii
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international clones (IC) and Acinetobacter nosocomialis have challenged healthcare (1,
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2). MDR phenotype in Acinetobacter has been related to class 1 and 2 integrons (3, 4, 5);
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class 2 integrons predominate in A. baumannii from Latin America (5, 6). This finding is
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possibly related to local clonal groups (6), a hypothesis not yet addressed. Class 2
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integron structure seems less diverse than class 1 (7), and is usually embedded within
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transposon Tn7 (5, 8).
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Four A. baumannii and one A. nosocomialis IC characterized by MLST has been
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described and spread in Rio de Janeiro, Brazil (9, 10). The purpose of the present study
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was to explore the association of class 2 integrons and gene cassettes with these clonal
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lineages. Between 2007-2008, 163 A. baumannii and 72 A. nosocomialis hospital isolates
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were investigated (10); 153 (94%) of the A. baumannii and 21 (29%) of the A.
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nosocomialis isolates were MDR. Among A. nosocomialis, antimicrobial resistance was
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higher for trimethoprim-sulphametoxazole (66%), cefepime (23%) and ciprofloxacin
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(23%) (10).
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The presence of class 1 and 2 integrons was screened in all isolates by multiplex-
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PCR with intI1 and intI2 gene-specific primers (11). The intI amplicons of two A.
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baumannii isolates were sequenced as controls. The variable region for intI2 gene
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positive isolates was characterized by amplification with primers Hep74 and Hep51 (12)
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and sequence analyses by BLAST (http://blast.ncbi.nlm.nih.gov/Blast.cgi). Isolates with
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no amplification of the variable region were further studied by PCR mapping with Hep74
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primer combined with dfrA1, sat2, aadA1 and aadB reverse primers, as described (13).
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PCR was additionally performed for Tn7 transposition genes (tnsA, tnsB, tnsC, tnsD and
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tnsE), where the 3’CS region is located (7). One positive amplicon of each tns gene was
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sequenced, as control.
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All isolates had been typed by RAPD-PCR (10), and a few by MLST (University
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of Oxford, UO and Institut Pasteur, IP schemes) (9, 10). In the present study, MLST was
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performed for all A. baumannii isolates. Proportions were compared by Fisher’s or chi-
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square test (http://www.openepi.com), p