Background and Objective:
Carbapenem-resistant Enterobacterales (CRE) infections are a major public health threat worldwide. The presence of NDM-producing-Klebsiella pneumoniae (NDM-KP) has increased in several regions, mainly during the COVID-19 pandemic. The study aimed at describing a regional outbreak of NDM-KP identified in bloodstream infections (BSI)in the Apulia region of Italy.

Methods:
From January 2020 to September 2022, 459 carbapenem-resistant-KP (CR-KP) strains collected from patients hospitalized with BSI were subjected to molecular characterization at the Laboratory of Molecular Epidemiology and Public Health of the University Hospital Policlinico of Bari (Italy) through a commercial multiplex real-time PCR kit (GeneXpert platform, Cepheid) for the identification of the carbapenemase-encoding genes blaKPC, blaVIM, blaNDM, blaIMP and blaOXA-48. In addition, a subset of 27 NDM-KP randomly selected strains were subjected to NDM variant detection by real-time PCR assay and to multi-locus sequence typing (MLST).

Results:
The blaKPC gene was identified in 67.5% of KP isolates, blaVIM in 0.2%, blaNDM in 20.3%, blaOXA-48 in 3.1%. Carriage of multiple carbapenemase genes was reported in 12 isolates (11 blaNDM+blaKPC and one blaKPC+blaVIM). Overall, 104 strains carrying the blaNDM gene were identified (22.6%). The 69.2% was identified in male subjects. The average age was 67 years (range: 29-92) and the province of residence was Brindisi for 35.6%, and Taranto for 41.3% of patients. Forty-four patients (42.3%) were positive for SARS-CoV-2. Further characterization of 27 NDM-KP strains revealed that all the strains were ST147-NDM-1-KP.

Conclusion:
The prevalence of NDM-KP in the Apulia region has increased from 0.2% in 2014-2016 to 22.6% in 2020-2022, thus representing a matter of concern. Implementation of molecular epidemiology of CRE is crucial to limit hospital infections. Moreover, timely and appropriate diagnosis, high standards of infection prevention and control, and antimicrobial stewardship are key actions to control the spread of antimicrobial resistance worldwide, particularly in hospital settings.