Profiling of 16S rRNA methylase genes and the flanking sequences in extensively drug resistant Pseudomonas aeruginosa / 中国感染与化疗杂志

ABSTRACT

Objective To profile 16S rRNA methylase genes and the flanking sequences in extensively drug resistant (XDR) Pseudomonas aeruginosa. Methods A total of 59 strains of XDR P. aeruginosa were collected. MICs of antimicrobial agents against these strains were determined by agar dilution method. The genes encoding 16S rRNA methylase (armA, rmtA, rmtB, rmtC, rmtD, rmtE, and npmA) were analyzed by PCR. The homology of strains was studied by enterobacterial repetitive intergenic consensus-polymerase chain reaction (ERIC-PCR). The structure of armA and rmtB flanking regions were characterized. Results The overall prevalence of armA or rmtB genes was 62.7％ (37/59) in XDR P. aeruginosa isolates, specifically armA positive in 17 strains and rmtB positive in 22 strains. The rmtA, rmtC, rmtD, or npmA gene was not identified in any strain. ERICPCR generated 19 types (or clones) from the 59 strains. The 17 armA-positive strains were distributed in 3 clones, and 88.2％ of the armA-positive strains (15) belonged to clone D. The rmtB gene was dispersed in 9 clones. Flanking sequence analysis demonstrated that armA gene was located in a mobile element carrying multiple transposases. The sequence of the mobile element showed 99％ similarity with the sequence of armA-positive plasmid carried by E. coli and A. baumannii. The rmtB gene was also located in a mobile element containing multiple transposases. The sequence of the mobile element was highly consistent with that of rmtB-positive plasmid carried by E. coli and K. pneumoniae. Conclusions The genes encoding 16S rRNA methylase are prevalent in XDR P. aeruginosa strains. All the genes were identified in high-level gentamicin-resistant strains. Clonal dissemination may explain the spread of armA among P. aeruginosa isolates.