Clinical and environmental investigation of six cases of Chryseobacterium arthrosphaerae infections in a Southern Italian hospital

Chryseobacterium spp. are Gram-negative, opportunistic pathogens antibiotic-resistant commonly found in the environment. The aim of this study was to investigate potential sources of Chryseobacterium infections in healthcare settings by comparing clinical and environmental isolates using phenotypic and genotypic analyses. Between June and July 2023, six cases of infection with Chryseobacterium spp. were identified in a hospital in Apulia, southern Italy. Environmental sampling (air, surfaces and water) was performed in parallel with routine clinical investigations. Isolates were subjected to antibiotic susceptibility testing and genotypic analysis using Sanger and Next-Generation Sequencing. Five cases of Chryseobacterium spp. infection were recorded in the Gastroenterology Department (Pavilion A) and one in the Vertebral Surgery Department (Pavilion B). C. indologenes was identified in blood and tracheal aspirate samples using MALDI-TOF MS. Environmental analysis carried out in the pavilions A and B isolated C. indologenes from sink tap in Pavilion B. Subsequently, genome sequencing revealed that Chryseobacterium strains misidentified as C. indologenes were more closely related to C. arthrosphaerae. Genetic analysis confirmed the cluster hypothesis involving four patients from the pavilion A, while no genetic link was found between the environmental and clinical strains. Innovative molecular methods in clinical and environmental investigations have allowed more accurate identification of the etiologic agent and possibly tracing the source of infection in the nosocomial setting. Control measures, such as patient isolation and room disinfection, have prevented the spread of infection.