Emergence of NDM-1-Producing Pseudomonas aeruginosa Nosocomial Isolates in Attica Region of Greece

Here, we report on the emergence and spread of multidrug-resistant NDM-1-producing <i>P. aeruginosa</i> isolates from patients hospitalized in the Attica region, Greece, in 2022 to provide data on their resistome, their virulome, the genetic environment of <i>bla</i>_NDM-1, and their molecular epidemiology. A total of 17 carbapenem-resistant <i>P. aeruginosa</i> isolates identified as NDM-producers by immunochromatography at the hospital level were sent to the Central Public Health Laboratory, in the frame of the laboratory surveillance of carbapenem-resistant pathogens, for further characterization. The initial screening for genetic AMR determinants was carried out by PCR and the MDR Direct Flow Chip assay. Typing was performed by MLST and DLST, the latter in a subset of isolates. Further analysis was performed by whole-genome sequencing (WGS) of six isolates from both hospitals to analyze their entire genomes and elucidate their genetic relatedness. All isolates were allocated to international high-risk clones, sixteen to ST773 and one to ST308. Five ST773 and the sole ST308 isolate were found to harbor the <i>bla</i>_NDM-1 gene, along with various other ARGs integrated into their chromosomes, as well as with a wide variety of virulence genes. The <i>bla</i>_NDM-1 gene was located in the integrative and conjugative elements ICE<i>6600</i>-like and ICE<i>_Tn43716385</i> in ST773 and ST308 isolates, respectively. Single-nucleotide polymorphism analysis of the five ST773 isolates indicated their clonal spread in both hospitals. These results suggested that two different molecular events contributed to the emergence of NDM-1-producing <i>P. aeruginosa</i> isolates in Athenian hospitals, highlighting the need for ongoing surveillance.