Ann Lab Med.  2014 Jul;34(4):293-299. 10.3343/alm.2014.34.4.293.

Epidemiological Characterizations of Class 1 Integrons from Multidrug-Resistant Acinetobacter Isolates in Daejeon, Korea

• Sung JY
• Koo SH
• Kim S
• Kwon KC

• KMID: 1791937
• DOI: http://doi.org/10.3343/alm.2014.34.4.293

Abstract

BACKGROUND
Multidrug-resistant (MDR) Acinetobacter spp. acquire antimicrobial agent-resistance genes via class 1 integrons. In this study, integrons were characterized to investigate the antimicrobial resistance mechanisms of MDR Acinetobacter isolates. In addition, the relationship between the integron type and integron-harboring bacterial species was analyzed by using epidemiological typing methods.
METHODS
Fifty-six MDR Acinetobacter spp.-A. baumannii (N=30), A. bereziniae (N=4), A. nosocomialis (N=5), and A. pittii (N=17)-were isolated. The minimum inhibitory concentrations (MICs) were determined on the basis of the results of the Epsilometer test (Etest). PCR and DNA sequencing was performed to characterize the gene cassette arrays of class 1 integrons. Multilocus sequence typing (MLST) and repetitive extragenic palindromic sequence (REP)-PCR were performed for epidemiological typing.
RESULTS
Class 1 integrons were detected in 50 (89.3%) of the 56 isolates, but no class 2 or 3 integron was found within the cohorts. The class 1 integrons were classified into 4 types: 2.3-kb type A (aacA4-catB8-aadA1), 3.0-kb type B (aacA4-blaI(MP-1)-bla(OXA-2)), 3.0-kb type C (bla(VIM-2)-aacA7-aadA1), and 1.8-kb type D (aac3-1-bla(OXA-2)-orfD). Type A was most prevalent and was detected only in A. baumannii isolates, except for one A. bereziniae isolate; however, type B was amplified in all Acinetobacter isolates except for A. baumannii isolates, regardless of clone and separation time of the bacteria.
CONCLUSIONS
Although class 1 integron can be transferred horizontally between unrelated isolates belonging to different species, certain types of class 1 integrons tend to transfer horizontally and vertically among A. baumannii or non-baumannii Acinetobacter isolates.

Keyword

MDR Acinetobacter spp.; Integron; MLST; Sequence types

MeSH Terms

Acinetobacter/drug effects/isolation & purification/*metabolism
Acinetobacter Infections/epidemiology/microbiology
Acinetobacter baumannii/drug effects/isolation & purification/metabolism
Anti-Bacterial Agents/pharmacology
DNA, Bacterial/chemistry/metabolism
Drug Resistance, Multiple, Bacterial
Humans
Integrons/*genetics
Microbial Sensitivity Tests
Multilocus Sequence Typing
Polymerase Chain Reaction
Republic of Korea
Anti-Bacterial Agents
DNA, Bacterial

Figure

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  Fig. 1 Repetitive extragenic palindromic (REP)-PCR patterns of genomic DNA from MDR Acinetobacter baumannii (top panel) and Acinetobacter pittii (bottom panel) isolates. Lane M, 1-kb DNA size marker.Abbreviations: MDR, multidrug resistant; ST, sequence type.

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