HOSPITAL TRANSMISSION OF KLEBSIELLA PNEUMONIAE CLONES IN ONCO-HEMATOLOGIC PATIENTS

Understanding the population structure of pathogens allows identification of circulating clones and transmission patterns, guiding detection of high-risk clones and control measures that can significantly improve prognosis, especially in highly vulnerable patients. In this study, we investigated the Klebsiella pneumoniae population isolated from gastrointestinal tract (GIT) colonization and bloodstream infections (BSI) in onco-hematologic patients, focusing on involved clones and potential cross-transmission events. Over 16 months, 33 K. pneumoniae strains were collected: 22 from BSI in 18 patients and 11 from GIT colonization in 9 patients, including isolates collected from the same patient at different times. All strains underwent whole-genome sequencing and analysis in the Pathogenwatch platform. Single nucleotide polymorphism (SNP) quantification in core genome genes enabled estimation of evolutionary divergence between strains of the same sequence type (ST), with fewer than 21 SNPs indicating close relatedness. Among the 17 STs identified, those detected more than once (n = 22) were ST11 (patients P34, P41, P61), ST13 (P45), ST307 (P25), ST441 (P27, P38, P39), ST15 (P10, P20), and ST111 (P40, P51, P54). Among these, we observed high genomic similarity (<10 SNPs) for ST11, ST13, ST307, ST441, and ST15 isolates from patient P20. However, the BSI ST15 strain from P10 differed by >300 SNPs from ST15 isolates in P20. For ST111, BSI isolates from P40 and P54 differed by <50 SNPs but diverged markedly from that of P51 (>400 SNPs). Notably, ST11 and ST13 carried the blaKPC-2 resistance gene, ST307 carried blaCTX-M-15, ST441 carried blaNDM-1, and ST15 carried blaKPC-2 in infection isolates and blaKPC-25 and/or blaNDM-1 in colonization isolates. These findings indicate circulation of high-risk and/or multidrug-resistant clones in the unit and reinforce the occurrence of cross-transmission events and translocation from GIT to bloodstream. Monitoring the clonal profile of K. pneumoniae in hematology units may contribute to effective surveillance, prevention, and control measures to limit hospital dissemination of these pathogens.