Characterization of 16S rRNA methylase genes in Enterobacterales andPseudomonas aeruginosain Athens Metropolitan area, 2015-2016

The aim of this study was to characterize the 16S rRNA methylase (RMT) genes in aminoglycoside-resistant Enterobacterales andPseudomonas aeruginosaisolates in 2015-2016 in hospitals in Athens, Greece. Single-patient, Gram-negative clinical isolates resistant to both amikacin and gentamicin (n= 292) were consecutively collected during a two-year period (2015-2016) in five tertiary care hospitals in Athens. RMT genes were detected by PCR. In all RMT-producing isolates, ESBL and carbapenemase production was confirmed by PCR, and the clonal relatedness and the plasmid contents were also characterized. None of the 138P. aeruginosaisolates harbored any of the RMT genes surveyed although some were highly resistant to aminoglycosides (MICs > = 512 mg/L). Among 154 Enterobacterales, 31Providencia stuartii(93.9%), 42Klebsiella pneumoniae(37.8%), sixProteus mirabilis(75%), and twoEscherichia coli(100%) isolates were confirmed as highly resistant to amikacin, gentamicin, and tobramycin with MICs >= 512 mg/L, harboring mainly thermtB(98.8%). All were carbapenemase producers.P. stuartii,P. mirabilis, andE. coliproduced VIM-type carbapenemases.K. pneumoniaeproduced KPC- (n= 34, 81.0%), OXA-48 (n= 4, 9.5%), KPC- and VIM- (n= 3, 7.1%), or only VIM-type (n= 1, 2.4%) enzymes. Two groups of similar IncC plasmids were detected one harboringrmtB1,bla(VEB-1),bla(OXA-10), andbla(TEM-1), and the other additionallybla(VIM-1)andbla(SHV-5). Among RMT-producing Enterobacterales,rmtB1predominated and was associated with carbapenemase-encoding gene(s). Similar IncC plasmids carrying a multiresistant region, including ESBL genes, and in the case of VIM-producing isolates, thebla(VIM-1), were responsible for this dissemination. The co-dissemination of these genes poses a public health threat.

Automated summary

This study aimed to characterize the 16S rRNA methylase (RMT) genes in aminoglycoside-resistant Enterobacterales and Pseudomonas aeruginosa isolates in hospitals in Athens, Greece in 2015-2016. It found highly resistant isolates with confirmed ESBL and carbapenemase production, with predominant rmtB1 gene in Enterobacterales and similar IncC plasmids responsible for gene dissemination, posing a public health threat.