Performance Evaluation of the IR Biotyper® System for Clinical Microbiology: Application for Detection of Staphylococcus aureus Sequence Type 8 Strains

Abstract

Background: Methicillin-resistant S. aureus (MRSA) clonal lineages have been classified based on sequence type (ST) and pulsotype associated with human infection. Providing rapid and accurate epidemiological insight is important to address proper infection control in both community-acquired and nosocomial hospital settings. In this regard, this study was performed to evaluate the IR Biotyper® (IRBT®) for strain typing of S. aureus clinical isolates on three media.

Methods: A total of 24 S. aureus clinical isolates comprising 15 MRSA isolates (six ST5, three ST72, three ST8, and three ST188 isolates) and nine methicillin-susceptible S. aureus (MSSA) isolates (three ST5, three ST72, and three ST8 isolates) were included for evaluating the IRBT®. Molecular characterization of all S. aureus isolates was performed by conventional PCR and sequencing methods. The IRBT® was evaluated according to manufacturer instructions and a modified sample procedure on commonly used BAP, MHA, and TSA media. Subsequently, the spectra obtained by IRBT® software were compared with dendrograms of PFGE analysis.

Results: In this study, the modified sample procedure for reducing the amount of bacteria and bacterial concentration improved the acquisition quality pass rate of the IRBT®. Each spectrum of S. aureus ST5, ST72, and ST188 isolates on all three media could not be clustered by IRBT®. However, the dendrogram obtained from the spectra of S. aureus ST8 isolates on TSA medium were in concordance with that obtained by PFGE analysis. In addition, the visual distribution of S. aureus ST8 isolates on TSA medium in a 2D scatter plot appeared as separated point set from those of S. aureus ST5, ST72, and ST188 isolates.

Conclusions: The IRBT® system is a rapid strain typing tool using the FTIR spectroscopic method. This system demonstrated the possibility of discriminating the strain types of S. aureus clinical isolates. Indeed, S. aureus ST8 isolates on TSA medium were successfully differentiated from other strain type isolates.