An evaluation of matrix-assisted laser desorption ionization time-of-flight mass spectrometry for the identification of Staphylococcus pseudintermedius isolates from canine infections

It has been proposed, based on taxonomic and molecular studies, that all canine isolates belonging to Staphylococcus intermedius group (SIG) should be renamed Staphylococcus pseudintermedius. However, isolates of SIG and other coagulase-positive staphylococci share many phenotypic characteristics, which could lead to misidentification. The accuracy of matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS) for identifying S. pseudintermedius isolates obtained from canine infections was evaluated, using a polymerase chain reaction (PCR)-based identification as the gold standard. In addition, MALDI-TOF MS was compared with conventional biochemical tests. A central problem was the incorrect identification of S. pseudintermedius isolates as S. intermedius by either MALDI-TOF MS or biochemical identification. From the 49 S. pseudintermedius isolates identified by the molecular method, only 21 could be assigned to this species by the biochemical approach and only 12 by MALDI-...