Worldwide distribution and environmental origin of the Adelaide imipenemase (AIM-1), a potent carbapenemase in Pseudomonas aeruginosa .

Carbapenems are potent broad-spectrum β-lactam antibiotics reserved for the treatment of serious infections caused by multidrug-resistant bacteria such as . The surge in resistant to carbapenems is an urgent threat, as very few treatment options remain. Resistance to carbapenems is predominantly due to the presence of carbapenemase enzymes. The assessment of 147 . isolates revealed that 32 isolates were carbapenem non-wild-type. These isolates were screened for carbapenem resistance genes using PCR. One isolate from wastewater contained the Adelaide imipenemase gene ( ) and was compared phenotypically with a highly carbapenem-resistant clinical isolate containing the gene. A further investigation of wastewater samples from various local healthcare and non-healthcare sources as well as river water, using probe-based qPCR, revealed the presence of the gene in all the samples analysed. The widespread occurrence of throughout Adelaide hinted at the possibility of more generally extensive spread of this gene than originally thought. A blast search revealed the presence of the gene in Asia, North America and Europe. To elucidate the identity of the organism(s) carrying the gene, shotgun metagenomic sequencing was conducted on three wastewater samples from different locations. Comparison of these nucleotide sequences with a whole-genome sequence of a isolate revealed that, unlike the genetic environment and arrangement in , the gene was not carried as part of any mobile genetic elements. A phylogenetic tree constructed with the deduced amino acid sequences of AIM-1 suggested that the potential origin of the gene in might be the non-pathogenic environmental organism, .