Application of Fourier-transform infrared spectroscopy for typing in a neonatal Kluyvera ascorbata clinical outbreak

Introduction. Despite not commonly found in clinical samples, Kluyvera ascorbata has the potential to cause clinically relevant infections, especially in healthcare settings. Typing methods have to be applied to recognize and track the transmissions and outbreaks. Fourier transform infrared spectroscopy (FT-IRS) is a recently introduced method for microbial typing on different intraspecies levels with the potential of a near-time monitoring due to its speed. In this study, we evaluate the applicability of FT-IRS methodology for the typing of a less common pathogen.

Methods. Sixteen strains of Kluyvera spp. were included in this study. Among them, n=10 K. ascorbata isolates collected during the routine screening of a neonatal intensive care unit (NICU) in September 2022, n=3 K. ascorbata reference strains from culture collections and the type strains of K. cryocrescens, K. georgiana and K. intermedia (total n=3). The strains collected during the screening underwent typing by PFGE, performed by the National Reference Center in Bochum, Germany. Eight out of ten screening K. ascorbata strains were typed by PFGE as belonging to the same pulsotype. FT-IRS analysis was performed with the IR Biotyper® system (IRBT; Bruker Daltonics, Germany). Spectra were acquired from 3 independent biological replicates, cultivated on Columbia blood agar (Becton Dickinson) at 37 °C for 24±2 h. Exploratory analysis for clustering was performed by Hierarchical Cluster Analysis (HCA) applying Euclidean average linkage.

Results. IR Biotyper HCA shows that the eight K. ascorbata outbreak isolates cluster together, in complete agreement with PFGE results (Figure 1). Further, the outbreak isolates resulted clearly differentiated from the two non-outbreak isolates, as well as from the three culture collection strains. Also, the type strains of the other Kluyvera species resulted well differentiated from K. ascorbata.

Conclusions. FT-IRS could successfully reveal the clonality among K. ascorbata outbreak isolates in this study. Due to its speed and ease-of-use the method has the potential to be applied in a routine setting for near-time monitoring in hospital hygiene.