Ann Lab Med.  2013 Jul;33(4):242-247. 10.3343/alm.2013.33.4.242.

Molecular Epidemiology of Integron-Associated Antimicrobial Gene Cassettes in the Clinical Isolates of Acinetobacter baumannii from Northern Taiwan

• Lin MF
• Liou ML
• Tu CC
• Yeh HW
• Lan CY

• KMID: 1707230
• DOI: http://doi.org/10.3343/alm.2013.33.4.242

Abstract

BACKGROUND
The aims of this study were to understand the molecular epidemiology of integron-associated gene cassettes in Acinetobacter baumannii across four hospitals in northern Taiwan and to clarify the relationship between the presence of integrons and antibiotic-resistant phenotypes.
METHODS
Sixty-five A. baumannii isolates, collected from the patients of four regional hospitals in northern Taiwan in 2009, were tested for the presence of integrons and their associated gene cassettes. The susceptibility difference between integron-positive and integron-negative A. baumannii strains was analyzed. Antibiotic-resistant phenotypes among A. baumannii with different types of gene cassette array combinations were also compared.
RESULTS
Around 72% of the A. baumannii isolates carried class 1 integrase genes. Despite this, only three gene cassette arrays were found in the integrons. Integron-positive strains were significantly more resistant to all the tested antibiotics than the integrase-negative strains. All the four types of A. baumannii with different gene cassette array combinations were multidrug-resistant in nature. Gene cassette array aacA4-catB8-aadA1 existed in all the integron-positive A. baumannii isolates. Repetitive-sequence-based PCR (rep-PCR) results revealed the prevalence of one major cluster of imipenem-resistant A. baumannii strains (84%) in the four regional hospitals.
CONCLUSIONS
The presence of integrons with associated antimicrobial resistance gene cassettes can be used as a representative marker of multidrug resistance in A. baumannii. Some prevalent gene cassette arrays may exist among epidemiologically unrelated A. baumannii strains.

Keyword

Acinetobacter baumannii; Integron; Antimicrobial

MeSH Terms

Acinetobacter Infections/epidemiology/*microbiology
Acinetobacter baumannii/drug effects/*genetics/isolation & purification
Anti-Bacterial Agents/pharmacology
Bacterial Proteins/genetics
DNA, Bacterial/analysis
Drug Resistance, Bacterial
Humans
Imipenem/pharmacology
Integrases/genetics
Integrons/*genetics
Microbial Sensitivity Tests
Multiplex Polymerase Chain Reaction
Taiwan/epidemiology
Anti-Bacterial Agents
Bacterial Proteins
DNA, Bacterial
Imipenem
Integrases

Figure

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  Fig. 1 Dendrogram of 38 imipenem-resistant Acinetobacter baumannnii isolates and A. baumannii ATCC19606. 84% (32/38) constitutes cluster I and 16% (6/38) constitutes cluster II at a similarity cut-off value of 80%. The integrase-containing isolates can further be categorized into type I-IV according to the combination of gene cassette arrays.

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