JAC Advance Access published online on July 7, 2008
Journal of Antimicrobial Chemotherapy, doi:10.1093/jac/dkn244
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Original research |
Occurrence and mechanisms of amikacin resistance and its association with β-lactamases in Pseudomonas aeruginosa: a Korean nationwide study
1 Department of Laboratory Medicine, College of Medicine, The Catholic University of Korea, Seoul, Korea 2 Department of Internal Medicine, College of Medicine, The Catholic University of Korea, Seoul, Korea 3 Division of Food Bioscience and Technology, College of Life Science and Biotechnology, Korea University, Seoul, Korea
Received 2 March 2008; returned 25 March 2008; revised 21 May 2008; accepted 23 May 2008
* Corresponding author. Tel: +82-2-590-1604; Fax: +82-2-592-4190; E-mail: yjpk{at}catholic.ac.kr
Objectives: We investigated the occurrence and mechanism of amikacin resistance and its association with various β-lactamase genes in Pseudomonas aeruginosa isolates.
Methods: Of the total 250 consecutive, non-duplicated isolates of P. aeruginosa, 55 isolates showed amikacin resistance. PCR amplification of genes for aminoglycoside (AG)-modifying enzymes [aac(3)-I, aac(3)-II/VI, aac(3)-III/IV, aac(6')-I, aac(6')-II, ant(2'')-I, ant(4')-II and aph(3')-VI], 16S rRNA methylases (rmtA, rmtB, rmtC and armA) and class 1 integrons was performed. In addition, we analysed the association of AG resistance genes with various β-lactamase genes.
Results and conclusions: In Korea, the amikacin resistance rate in P. aeruginosa was high (22%), and it varied among provinces (3.8% to 40%). Four types of AG-modifying enzyme genes [aph(3')-VI, ant(2'')-I, aac(6')-I and aac(3)-II/VI] were found in 48 isolates. Thirty-six strains harboured two or more types of enzymes, of which a combination of aph(3')-VI and ant(2'')-I was the most frequent (24/36 isolates, 66.7%). None harboured aac(3)-I, aac(3)-III/IV, aac(6')-II, ant(4')-II, rmtA, rmtB, rmtC or armA. Forty-two isolates co-harboured β-lactamase genes (mostly blaOXA-10). A class 1 integron was detected in all but one, and all the ant(2'')-I and 26/29 blaOXA-10 were found in it. In contrast, aph(3')-VI was not found to be associated with the class 1 integron. Considering the possibility of co-selection and dissemination, constant monitoring of resistance evolution is necessary.
Key Words: aminoglycoside-modifying enzymes , aph(3')-VI , β-lactamases , integrons