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Antimicrobial Agents and Chemotherapy, January 2009, p. 104-111, Vol. 53, No. 1
0066-4804/09/$08.00+0     doi:10.1128/AAC.00852-08
Copyright © 2009, American Society for Microbiology. All Rights Reserved.

Widespread Dissemination of Aminoglycoside Resistance Genes armA and rmtB in Klebsiella pneumoniae Isolates in Taiwan Producing CTX-M-Type Extended-Spectrum β-Lactamases {triangledown}

Ling Ma,1 Chi-Jan Lin,1,2 Jiun-Han Chen,3 Chang-Phone Fung,4 Feng-Yee Chang,5 Yiu-Kay Lai,2 Jung-Chung Lin,5* L. K. Siu,1,5* and the Taiwan Surveillance of Antimicrobial Resistance Project

Division of Clinical Research, National Health Research Institutes, Zhunan Town, Miaoli County,1 Department of Life Science and Institute of Biotechnology, National Tsing Hua University, Hsinchu,2 Department of Medical Laboratory Science and Biotechnology, Yuanpei University, Hsinchu,3 Department of Medicine, Chutung Veterans Hospital, and National Yang-Ming University, Taipei,4 Division of Infectious Disease and Tropical Medicine, Department of Internal Medicine, Tri-Service General Hospital, National Defense Medical Center, Taipei, Taiwan5

Received 26 June 2008/ Returned for modification 9 September 2008/ Accepted 10 October 2008

Among 235 extended-spectrum β-lactamase-producing Klebsiella pneumoniae (ESBL) isolates collected from a nationwide surveillance performed in Taiwan, 102 (43.4%) were resistant to amikacin. Ninety-two of these 102 (90.2%) isolates were carrying CTX-M-type β-lactamases individually or concomitantly with SHV-type or CMY-2 β-lactamases. The armA and rmtB alleles were individually detected in 44 and 37 of these 92 isolates, respectively. One isolate contained both armA and rmtB. The coexistence of the aac(6')-Il and rmtB genes was detected in three isolates. CTX-M-type β-lactamase genes belonging to either group 1 (CTX-M-3 and CTX-M-15) or group 9 (CTX-M-14) were found in all armA- or rmtB-bearing ESBL-producing K. pneumoniae isolates, and all were conjugatively transferable. All except one of the isolates bearing armA produced CTX-M enzymes of group 1, and the remaining isolate bearing armA produced a group 9 CTX-M-type β-lactamase. On the contrary, in the majority of rmtB carriers, the CTX-M-type β-lactamase belonged to group 9 (62.2%). Molecular typing revealed that the amikacin-resistant ESBL-producing K. pneumoniae isolates were epidemiologically unrelated, indicating that the acquisition of resistance was not through the spread of a resistant clone or a resistance plasmid. A tandem repeat or multiple copies of blaCTX-M-3 were found in some armA-bearing isolates. An ISEcp1 insert was found in all CTX-M ESBL-producing K. pneumoniae isolates carrying armA or rmtB. In conclusion, the concomitant presence of a 16S rRNA methylase gene (armA or rmtB) and blaCTX-M among amikacin-resistant ESBL-producing K. pneumoniae isolates is widespread in Taiwan.

* Corresponding author. Mailing address for L. K. Siu: Division of Clinical Research, National Health Research Institutes, 35, Keyan Road, Zhunan Town, Miaoli County 350, Taiwan. Phone: 886 37 246166, ext. 35507. Fax: 886 37 586457. E-mail: lksiu{at}nhri.org.tw. Mailing address for Jung-Chung Lin: Division of Infectious Disease and Tropical Medicine, Department of Internal Medicine, Tri-Service General Hospital, National Defense Medical Center, Taipei 114, Taiwan. Phone: 886 2 87927257. Fax: 886 2 87927258. E-mail: linjungchung1{at}yahoo.com.tw

{triangledown} Published ahead of print on 20 October 2008.

Antimicrobial Agents and Chemotherapy, January 2009, p. 104-111, Vol. 53, No. 1
0066-4804/09/$08.00+0     doi:10.1128/AAC.00852-08
Copyright © 2009, American Society for Microbiology. All Rights Reserved.





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