Epidemiological typing of methicillin-resistant Staphylococcus aureus strains by Fourier transform infrared spectroscopy

A rapid and simple typing system is needed for controlling the spread of epidemic methicillin-resistant Staphylococcus aureus (MRSA), currently one of the most widespread multi-resistant nosocomial pathogens in Canadian hospitals. Fourier transform infrared (FTIR) spectroscopy was used to subtype 85 isolates representing five strains of epidemic Canadian MRSA (CMRSA). Spectral fingerprints of whole cells grown on Que-Bact® Universal Medium No. 2 were transformed to first derivative peak-height normalized files and examined visually and by singular-value decomposition (SVD). Distinguishing spectral regions were processed by principal component analysis (PCA), self-organizing map and K-nearest neighbor supervised cluster analysis. Among the visually identified regions, 1070–1050 and 1155–1137 cm− 1 were found suitable for discrimination of CMRSA-4 and CMRSA-2 respectively, while CMRSA-1, CMRSA-3, and CMRSA-5 each exhibited distinctive spectral profiles in the 1123–1094 cm− 1 region. The combination, 1123–1094, 1174–1154 and 2904–2864 cm− 1 separated the five CMRSA with 84.6% correct classification by PCA. Five clusters were also obtained using the SVD-selected regions 1096–1066, 1118–1090 and 2914–2880 cm− 1, with 87.8% correct classification based on visual examination of the PCA scores plot and 97% based on supervised cluster analysis. These results demonstrate that FTIR spectroscopy has considerable potential as a rapid (1-hour) and simple method for MRSA strain typing and monitoring in clinical settings.