Dynamics of carbapenemase-producing Enterobacterales intestinal colonisation in the elderly population after hospital discharge, Italy, 2018-2020.

Carbapenemase-producing Enterobacterales (CPE) represent a serious threat to public health worldwide. Elderly patients are at increased risk of colonisation/infection with CPE. This study aimed to evaluate the persistence of CPE colonisation and the genotypic characteristics of persistent strains in elderly people discharged from Italian hospitals. A longitudinal study was conducted in two Italian cities (March 2018 to September 2020) enrolling 137 patients aged ≥65 years with CPE intestinal colonisation at hospital discharge. CPE colonisation was evaluated after 4, 8 and 12 months. Competing risk analysis was used to explore the association between baseline characteristics and persistence at 4 months. For all isolates, carbapenemase typing and multilocus sequence typing were performed. Persistent isolates underwent whole-genome sequencing. Of 137 patients, 91% carried carbapenemase-producing Klebsiella pneumoniae (CP-KP) and 8.8% carried carbapenemase-producing Escherichia coli. Although a large number of patients were lost to follow-up owing to death or withdrawal, 28/65 patients (43.1%) remained colonised at Month 4; 16/42 (38.1%) and 5/28 (17.9%) were found colonised up to Months 8 and 12, respectively. Colonisation persistence was more frequent in patients with bacteraemia or complicated urinary tract infection while in hospital and in those staying in long-term care facilities (LTCFs). Clonal characteristics of CP-KP isolates did not appear to influence persistence. Isolates obtained from each persistent carrier were identical or highly related by SNP phylogenetic analysis. Identification of patients at higher risk of persistent intestinal carriage after hospital discharge can prompt control measures to limit the transmission of CPE in the community, especially in LTCF settings.