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Open Access Research article

Emergence of 16S rRNA methylase-producing Acinetobacter baumannii and Pseudomonas aeruginosa isolates in hospitals in Vietnam

Tatsuya Tada1, Tohru Miyoshi-Akiyama1, Yasuyuki Kato2, Norio Ohmagari3, Nozomi Takeshita3, Nguyen Viet Hung4, Doan Mai Phuong4, Truong Anh Thu4, Nguyen Gia Binh4, Nguyen Quoc Anh4, Tran Thi Thanh Nga5, Pham Hong Truong5, Phan Thi Xuan5, Le Thi Anh Thu5, Nguyen Truong Son5 and Teruo Kirikae1*

Author Affiliations

1 Department of Infectious Diseases, National Center for Global Health and Medicine, Shinjuku, Tokyo 162-8655, Japan

2 Disease Control and Prevention Center, National Center for Global Health and Medicine, Shinjuku, Japan

3 Disease Control and Prevention Center, Division of Infectious Diseases, National Center for Global Health and Medicine, Shinjuku, Japan

4 Bach Mai Hospital, Hanoi, Vietnam

5 Cho Ray Hospital, Ho Chi Minh, Vietnam

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BMC Infectious Diseases 2013, 13:251  doi:10.1186/1471-2334-13-251

Published: 30 May 2013

Abstract

Background

16S rRNA methylase-producing Gram-negative bacteria are highly resistant to all clinically important aminoglycosides. We analyzed clinical strains of 16S rRNA methylase-producing Acinetobactor baumannii and Pseudomonas aeruginosa obtained from clinical isolates in medical settings in Vietnam.

Methods

From 2008 to 2011, 101 clinical strains of A. baumannii and 15 of P. aeruginosa were isolated from patients in intensive care units (ICUs) in two medical settings in Vietnam. Antimicrobial susceptibilities were determined using the microdilution method and epidemiological analysis was performed by pulsed-field gel electrophoresis and MLST. Genes encoding the 16S rRNA methylases, OXAs and CTX-Ms were analyzed by PCR and sequence analysis.

Results

16S rRNA methylase-producing Gram-negative pathogens were detected in two hospitals in Vietnam. Of the 101 clinical isolates of A. baumannii and the 15 of P. aeruginosa isolated from two ICUs in these hospitals, 72 (71.3%) were highly resistant to amikacin, arbekacin and gentamicin, with MICs greater than 1,024 mg/L. The 16S rRNA methylases ArmA and RmtB were produced by 61 and 9 isolates of A. baumannii, respectively, and RmtB was produced by 2 isolates of P. aeruginosa. Moreover, 52 of the A. baumannii isolates producing 16S rRNA methylases harbored both blaOXA-23-like and blaOXA-51-like genes. Most A. baumannii isolates producing 16S rRNA methylase obtained in hospital A in Hanoi were ST91 and ST231, whereas most from hospital B in Ho Chi Minh City were ST136, ST195, and ST254.

The two P. aeruginosa isolates harboring rmtB showed different patterns on PFGE, one each corresponding to ST217 and ST313.

Conclusions

Gram-negative bacteria producing the 16S rRNA methylases ArmA and RmtB are emerging in medical settings in Vietnam. A. baumannii isolates in northern and southern regions of Vietnam may be of different lineages.

Keywords:
Acinetobacter baumannii; Pseudomonas aeruginosa; Aminoglycoside resistance; Intensive care unit; 16S rRNA methylase