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Epidemiological characterizations of class 1 integrons from multidrug-resistant acinetobacter isolates in Daejeon,
Ji Youn Sung1, Sun Hoe Koo2, Semi Kim2
1Department of Biomedical Laboratory Science, Far East University, Eumseong, Korea.
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.
Insights
Class 1 integrons are key to multidrug resistance in Acinetobacter species. Specific integron types show distinct patterns of horizontal and vertical transfer among Acinetobacter baumannii and other Acinetobacter species.
Area of Science:
- Microbiology
- Genetics
- Molecular Biology
Background:
- Multidrug-resistant (MDR) Acinetobacter species frequently acquire antimicrobial resistance genes through class 1 integrons.
- Understanding integron mechanisms is crucial for combating MDR Acinetobacter infections.
Purpose of the Study:
- To characterize integrons in MDR Acinetobacter isolates.
- To investigate antimicrobial resistance mechanisms.
- To analyze the relationship between integron types and bacterial species using epidemiological methods.
Main Methods:
- Isolation and identification of 56 MDR Acinetobacter spp. (A. baumannii, A. bereziniae, A. nosocomialis, A. pittii).
- Determination of minimum inhibitory concentrations (MICs) using Etest.
- PCR and DNA sequencing to characterize class 1 integron gene cassette arrays.
- Multilocus sequence typing (MLST) and REP-PCR for epidemiological typing.
Main Results:
- Class 1 integrons were prevalent, found in 89.3% of isolates; no class 2 or 3 integrons were detected.
- Four types of class 1 integrons were identified: Type A (2.3-kb), Type B (3.0-kb), Type C (3.0-kb), and Type D (1.8-kb).
- Type A integrons were most common in A. baumannii, while Type B integrons were found in non-baumannii Acinetobacter species.
Conclusions:
- Class 1 integrons can transfer horizontally between different Acinetobacter species.
- Specific class 1 integron types exhibit preferential horizontal and vertical transmission within A. baumannii or among non-baumannii Acinetobacter species.
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