Characterization of an Outbreak of Extended-Spectrum β-Lactamase-Producing Klebsiella pneumoniae in a Neonatal Intensive Care Unit in Italy.

Here we report an outbreak of extended spectrum β-lactamase-producing Klebsiella pneumoniae that occurred in a neonatal intensive care unit in Northern Italy and involved 97 patients. Progressively tightened sets of containment measures were implemented but the epidemic event was stopped only 9 months later. The final, effective, containment strategy consisted of the application of strict geographic cohorting of colonized infants and their nursing staff, the suspension of any new admission and a rigorous daily sterilization protocol for all surfaces and fomites in the ward. A posteriori characterization of the outbreak strain was performed using both traditional microbiology and molecular biology techniques, and whole genome sequencing, allowing to compare outbreak isolates with other strains collected in the previous two years. The results allowed to determine that the outbreak strain had been circulating inside the ward since the year before. Genomic characterization revealed that the strain carried a wide array of virulence and antibiotic resistance determinants, including gene bla, which had never been reported in a clinical isolate of K. pneumoniae before. The presence of such a high number of determinants for antibiotic resistance imposes significant therapeutic limitations on the treatment of infections, thus, further epidemiological investigations are needed to evaluate the prevalence of the newly described variant.