Emergence and inter-hospital circulation of capsule K2- and OXA-48-producing Klebsiella pneumoniae ST395 in north-eastern Italy

Objective: Klebsiella pneumoniae ST395 is an internationally disseminated, high-risk clone implicated in OXA-48-producing K. pneumoniae (OXA-48 Kp) outbreaks. In Italy, K. pneumoniae ST395 is sporadically detected and mainly associated with the blaKPC-3 determinant. Here we aimed to explain the increase in cases of OXA-48 Kp ST395 in north-eastern Italy. Methods: In the period May–July 2024, 57 OXA-48 Kp samples were collected from three different hospitals and related communities within the province of Venice, Italy. Species identification, antimicrobial susceptibility, carbapenemase production, and clonal relatedness were ascertained using MALDI-TOF MS, the Vitek-2 System, CARBA PLUS (MASTGroup), and pulsed-field gel electrophoresis, respectively. Whole-genome sequencing was carried out on seven representative strains using an Illumina (San Diego, CA, USA) NovaSeq. Results: All 57 OXA-48 Kp strains retained susceptibility to aminoglycosides only, with three pulsotypes (A–C) detected by pulsed-field gel electrophoresis. Pulsotype A included 13 subtypes (A–A12). Subtypes A3 and A9 (n = 8, respectively) had the highest pattern similarity, followed by A12 (n = 4), A5 (n = 3), and A11 (n = 2). ST395 and the K2 capsule were highlighted by whole-genome sequencing. The shared resistome consisted of aminoglycoside (aac(3)-IIa, aac(6′)-Ib-cr), chloramphenicol (catA1, catB4), beta-lactam (blaCTX−M-15), and carbapenem (blaOXA-48) genes. SNP-based phylogeny showed relevant genomic relatedness, although clonal identity was obtained in only two cases. Conclusions: Here we have highlighted the alarming inter-hospital circulation of OXA-48 Kp ST395 in north-eastern Italy.