Emergence and clonal spread of NDM-1-producing Pseudomonas aeruginosa isolates in Greece

Multidrug-resistant carbapenemase-producing Pseudomonas aeruginosa (CPPA) poses a great challenge to clinical treatment. Since the emergence of carbapenemase-producing Pseudomonas aeruginosa in Greece, VIM-producers have predominated. This study describes the first occurrence and molecular characterization of NDM-1-producing P. aeruginosa in Greece. A total of 18 carbapenem-resistant P. aeruginosa isolates, recovered from patients at 3 hospitals in Attica region during 2022, were referred to the Central Public Health laboratory, as NDM producers by immunochromatography, for confirmation and further characterization. Antimicrobial susceptibility testing was performed using the VITEK- 2 system and broth microdilution method. Genetic relatedness was assessed using multilocus sequence typing. Whole genome sequencing (WGS) was carried out to six isolates to analyze the entire genome of the emerging pathogens. All 18 CPPA isolates carried the blaNDM-1 gene and exhibited high level resistance to ß-lactams, aminoglycosides, and ciprofloxacin. All but one was allocated to ST773 and co-harbored the 16S rRNA methylase rmtB conferring resistance to all aminoglycosides . The emergence and clonal spread of the NDM-1-producing P. aeruginosa ST773 isolates at 3 hospitals in Greece, prompted a national multicenter study to monitor the evolving molecular epidemiology of CPPA and assess the current situation to inform for both empirical treatment and public health actions.