Detection and characterisation of 16S rRNA methyltransferase-producing Pseudomonas aeruginosa from the UK and Republic of Ireland from 2003–2015.

• 8.6% (19/221) of pan-aminoglycoside-resistant Pseudomonas aeruginosa had 16S RMTase genes. • 16S RMTase gene variants rmtB4, rmtD3 and rmtF2 were detected. • 89.5% (17/19) of 16S RMTase gene-positive isolates harboured a carbapenemase gene. • P. aeruginosa 'high-risk' clones ST357, ST654 and ST773 harboured 16S RMTase genes. • Novel genetic environments for rmtB1, rmtC and rmtF2 were identified. 16S rRNA methyltransferase (16S RMTase) genes confer high-level aminoglycoside resistance, reducing treatment options for multidrug-resistant Gram-negative bacteria. Pseudomonas aeruginosa isolates (n = 221) exhibiting high-level pan-aminoglycoside resistance (amikacin, gentamicin and tobramycin MICs ≥64, ≥32 and ≥32 mg/L, respectively) were screened for 16S RMTase genes to determine their occurrence among isolates submitted to a national reference laboratory from December 2003 to December 2015. 16S RMTase genes were identified using two multiplex PCRs, and whole-genome sequencing (WGS) was used to identify other antibiotic resistance genes, sequence types (STs) and the genetic environment of 16S RMTase genes. 16S RMTase genes were found in 8.6% (19/221) of isolates, with rmtB4 (47.4%; 9/19) being most common, followed by rmtD3 (21.1%; 4/19), rmtF2 (15.8%; 3/19) and single isolates harbouring rmtB1, rmtC and rmtD1. Carbapenemase genes were found in 89.5% (17/19) of 16S RMTase-positive isolates, with bla VIM (52.9%; 9/17) being most common. 16S RMTase genes were found in 'high-risk' clones known to harbour carbapenemase genes (ST233, ST277, ST357, ST654 and ST773). Analysis of the genetic environment of 16S RMTase genes identified that IS 6100 was genetically linked to rmtB1 ; IS 91 to rmtB4, rmtC or rmtD3; IS CR14 to rmtD1 ; and rmtF2 was linked to Tn 3 , IS 91 or Tn 1721. Although 16S RMTase genes explained only 8.6% of pan-aminoglycoside resistance in the P. aeruginosa isolates studied, the association of 16S RMTase genes with carbapenemase-producers and 'high-risk' clones highlights that continued surveillance is required to monitor spread as well as the importance of suppressing the emergence of dually-resistant clones in hospital settings. [ABSTRACT FROM AUTHOR]