Plasmid-mediated 16S rRNA methylase in Serratia marcescens conferring high-level resistance to aminoglycosides.
Serratia marcescens S-95, which displayed an unusually high degree of resistance to aminoglycosides, including kanamycins and gentamicins, was isolated in 2002 from a patient in Japan. The resistance was mediated by a large plasmid which was nonconjugative but transferable to an Escherichia coli recipient by transformation. The gene responsible for the aminoglycoside resistance was cloned and sequenced. The deduced amino acid sequence of the resistance gene shared 82% identity with RmtA, which was recently identified as 16S rRNA methylase conferring high-level aminoglycoside resistance in Pseudomonas aeruginosa. Histidine-tagged recombinant protein showed methylation activity against E. coli 16S rRNA. The novel aminoglycoside resistance gene was therefore designated rmtB. The genetic environment of rmtB was further investigated. The sequence immediately upstream of rmtB contained the right end of transposon Tn3, including bla(TEM), while an open reading frame possibly encoding a transposase was identified downstream of the gene. This is the first report describing 16S rRNA methylase production in S. marcescens. The aminoglycoside resistance mechanism mediated by production of 16S rRNA methylase and subsequent ribosomal protection used to be confined to aminoglycoside-producing actinomycetes. However, it is now identified among pathogenic bacteria, including Enterobacteriaceae and P. aeruginosa in Japan. This is a cause for concern since other treatment options are often limited in patients requiring highly potent aminoglycosides such as amikacin and tobramycin.
Doi
Yohei
Y
Department of Bacterial Pathogenesis and Infection Control, National Institute of Infectious Diseases, Tokyo, Japan. yohei@nih.go.jp
Yokoyama
Keiko
K
Yamane
Kunikazu
K
Wachino
Jun-Ichi
J
Shibata
Naohiro
N
Yagi
Tetsuya
T
Shibayama
Keigo
K
Kato
Haru
H
Arakawa
Yoshichika
Y
D000368:Aged; D000595:Amino Acid Sequence; D000617:Aminoglycosides / Q000494:pharmacology*; D000900:Anti-Bacterial Agents / Q000494:pharmacology; D003001:Cloning, Molecular; D004269:DNA, Bacterial / Q000096:biosynthesis / Q000235:genetics / Q000302:isolation & purification; D003982:Dibekacin / Q000031:analogs & derivatives* / Q000494:pharmacology; D024881:Drug Resistance, Bacterial; D004926:Escherichia coli / Q000235:genetics; D006639:Histidine / Q000378:metabolism; D006801:Humans; D008297:Male; D008745:Methylation; D008826:Microbial Sensitivity Tests; D008969:Molecular Sequence Data; D010957:Plasmids / Q000235:genetics*; D012336:RNA, Ribosomal, 16S / Q000235:genetics*; D012270:Ribosomes / Q000737:chemistry; D016868:Serratia Infections / Q000382:microbiology; D012706:Serratia marcescens / Q000201:enzymology* / Q000235:genetics*; D012359:tRNA Methyltransferases / Q000235:genetics*
D000617:Aminoglycosides; D000900:Anti-Bacterial Agents; D004269:DNA, Bacterial; D012336:RNA, Ribosomal, 16S; D003982:Dibekacin; D006639:Histidine; D012359:tRNA Methyltransferases; C031986:arbekacin