A fast and reliable identification of Streptococcus spp. and mastitis associated other gram positive, catalase negative cocci (PNC) is still a challenge for routine diagnostics. Classical, phenotypic methods mainly detect major pathogens. Serological or biochemical detection methods are also only limited suitable for identification of PNCs.
Therefore novel physico - chemical diagnostic tools, such as Fourier-transform infrared (FTIR) spectroscopy and of Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF/MS) were testet in order to assess the suitability and applicability for routine diagnostics. A total of 210 PNC isolates were used to develop a spectral reference database and to establish an Artificial Neural Network (ANN) based on FTIR spectra. The external validation yielded 100 % correct species identification by combining ANN and the reference library. MALDI-TOF/MS also achieved an accuracy of 95.2 %. Both FTIR spectroscopy and MALDI-TOF/MS are suitable for routine diagnostics also confirmed by high identification results of blind study. Additionally, FTIR spectroscopy can be used for epidemiological studies and subtyping. Both methods are accurate and fast diagnostic tools and represent proper alternatives to traditional approaches.
Regarding the different discriminatory power of these methods, it depends on the research question which technique will be preferred.
Furthermore methods usually used in routine laboratories and alternatives methods were checked for their practicability. Only the combination of conventional and molecular methods enabled the identification of all mastitis relevant PNCs. The established flow chart based on a method mix provides a guideline for the identification of these microorganisms at species level.