Fig. 4

Hierarchical cluster analysis of FTIR spectra recorded from A. pleuropneumoniae serotype 2 re-isolated from different organs of infected pigs. Isolates from different organs of the infected pigs 1–6 (I1-I6) and the strain used for infection were grown for 24 h on PPLO at 37 °C and 5% CO₂, subsequently subjected to FTIR spectroscopy and hierarchical cluster analysis was performed. For calculation of the dendrogram the FTIR spectral regions of 1150 to 1100 cm⁻¹ and the Ward’s algorithm were used A. pleuropneumoniae re-isolated from the lung of all six animals (I1-6) group and the inoculation strain group together in cluster (a), while the bacteria isolated from the tonsils and the nostrils group in cluster (b–d)