Abstract
Background16S 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.MethodsFrom 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.Results16S 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.ConclusionsGram-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.
Highlights
16S rRNA methylase-producing Gram-negative bacteria are highly resistant to all clinically important aminoglycosides
Bacterial strains From 2008 to 2011, 50 clinical strains of A. baumannii and 15 of P. aeruginosa were isolated from patients in an intensive care units (ICUs) in hospital A in Hanoi, Vietnam; and 51 strains of A. baumannii were isolated from patients in an ICU in hospital B in Ho Chi Minh City, Vietnam
Isolates from Clusters I, III, IV, V, VI, VII, and VIII were obtained from either one or the other hospital, whereas isolates from Clusters II and III were obtained from both. These results indicate that A. baumannii isolates had expanded in a clonal manner in both hospitals and that some isolates may spread among hospitals in Vietnam
Summary
16S rRNA methylase-producing Gram-negative bacteria are highly resistant to all clinically important aminoglycosides. Enzymatic modification [1] and the methylation of 16S rRNA makes these bacteria highly resistant to all clinically important aminoglycosides [2]. In 2003, clinical isolates of highly aminoglycoside-resistant Gram-negative bacteria producing16S rRNA methylase were identified in France [3] and Japan [4]. 16S rRNA methylase-producing Gram-negative bacteria have been isolated in other parts of the world, including Asian countries such as Afghanistan, Bangladesh, China, Hong Kong, India, Japan, Korea, Oman and Pakistan [5]. Since 2003, eight plasmid-associated 16S rRNA methylase genes, armA, rmtA, rmtB, rmtC, rmtD, rmtE, rmtF and npmA, have been identified in clinical and veterinary isolates from various geographic areas, including East Asia, Europe and the Americas, since 2003 [5,6]
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