Novel resistance ICEs carrying the bla FIM-1 metallo-β-lactamase gene from an ST235 Pseudomonas aeruginosa sublineage.

FIM-1 is an acquired metallo-β-lactamase identified in a multidrug-resistant Pseudomonas aeruginosa (index strain FI-14/157) of clinical origin isolated in 2007 in Florence, Italy. Here we report on a second case of infection by FIM-1-positive P. aeruginosa (FI-17645), which occurred in 2020 in the same hospital. Both FIM-1-positive strains exhibited resistance to all anti- Pseudomonas antibiotics except colistin and cefiderocol. Comparative genomic characterization revealed that the two FIM-positive strains were closely related [core genome difference, 16 single nucleotide polymorphisms (SNPs)], suggesting a local circulation of similar strains. In the FI-14/157 index strain, the bla FIM-1 gene was associated with an IS CR19 -like element that likely contributed to its capture downstream an integron platform inserted aboard a Tn 21 -like transposon, named Tn 7703.1 , which was associated with a large integrative and conjugative element (ICE) named ICE 7705 .1, integrated into an att site located within the 3'-end of tRNA Gly CCC gene of the P. aeruginosa chromosome. In strain FI-17645, bla FIM-1 was associated with a closely related ICE, named ICE 7705 . 2 , integrated in the same chromosomal site. Similar ICE platforms, lacking the bla FIM-1 -containing region, were detected in other ST235 P. aeruginosa strains from different geographic areas, suggesting a common ancestry and underscoring the role of these elements in the dissemination of resistance genes in P. aeruginosa . Sequence database mining revealed two draft P. aeruginosa genomes, one from Italy and one from the USA (both isolated in 2012), including a contig with bla FIM-1 , suggesting that this resistance gene could have a broader distribution than originally anticipated.