Challenging the problematic detection of clostridial isolates causing late-blowing defect with MALDI-TOF MS

The present study aimed to evaluate the Clostridium spp. counts in corn silage, raw milk and Kaşar cheese and to identify the clostridial isolates causing a late-blowing defect (LBD) potential using matrix-assisted laser desorption-ionization-time of flight mass spectrometry (MALDI-TOF MS). Lactate-fermenting clostridial spores (LFCS) were determined by the most probable number method (MPN) in 14 samples of corn silage, 12 samples of raw milk and 20 samples of Kaşar cheese. 181 isolates were obtained from MPN gas-positive tubes. Gram staining, catalase and oxidase activity, anaerobic development tests and Scanning Electron Microscopy (SEM) imaging showed that 95 isolates were typical clostridial bacteria. Sixty-six isolates could maintain viability during the passage and stock stages. A confirmatory identification technique was then performed using MALDI-TOF MS. The results revealed that (49 out of 66 isolates) of bacteria were correctly identified as 38 (77.55%) Clostridium sporogenes, 6 (12.24%) Clostridium butyricum, 3 (6.12%) Clostridium beijerinckii, 1 (2.04%) Clostridium bifermentans and 1 (2.04%) Clostridium sartagoforme. This study determined that clostridial isolates that cause LBD can be identified successfully and quickly by MALDI-TOF MS, a novel method for detecting anaerobic bacteria.