Evaluation of Fourier transform infrared spectroscopy as a first-line surveillance typing tool for Serratia spp. isolates derived from clinical materials.

INTRODUCTION: Fourier transform infrared spectroscopy (FTIR) has been evaluated as a typing method for a number of pathogens; however, very little research has been conducted on the genus Serratia. METHODS: We examined whether FTIR was able to correctly cluster clinical isolates of Serratia to a comparable degree as whole genome sequencing (WGS) coupled with a subsequent bioinformatic comparison, the gold standard for determining phylogenetic relationships in epidemiology. FTIR was performed with the IR Biotyper (Bruker, Bremen, Germany) using the standard settings. Over a period of six weeks, 28 Serratia isolates found in clinical and environmental hygiene samples investigated in our laboratory were collected and preserved. Retrospective strain typing was performed using both methods, and the results were subsequently compared. RESULTS: Our study showed a PPV of 0.842 for the correct identification of closely related isolates and an NPV of 1.0 for the correct identification of unrelated isolates. Concordance was measured using the Adjusted Rand index (AR) and the Adjusted Wallace coefficient (AW), with WGS and subsequent bioinformatic analysis as the reference method. This resulted in an AR of 0.742. DISCUSSION: Our findings indicate, although with some limitations, the utility of using the IR Biotyper as a rapid and cost-effective first-line screening tool for investigating the epidemiological relatedness of Serratia spp. in a clinical microbiology laboratory when an outbreak is suspected. Consequently, the FTIR method may provide a complementary analytical addition to the arsenals of clinical microbiology laboratories that carry out epidemiological surveillance to aid infection control in clinical settings.