Identification of spp. derived from a sheep and cattle slaughterhouse by matrix-assisted laser desorption and ionization-time of flight mass spectrometry (MALDI-TOF MS) and 16S rDNA sequencing.

Unlabelled: Clostridia are widespread and some of them are serious human pathogens. Identification of spp. is important for managing microbiological risks in the food industry. Samples derived from sheep and cattle carcasses from a slaughterhouse in Iran were analyzed by MALDI-TOF MS using direct transfer and extended direct transfer sample preparation methods and 16S rDNA sequencing. MALDI-TOF MS could identify ten species in 224 out of 240 isolates. In comparison to the 16S rDNA sequencing, correct identification rate of the spp. at the species level by MALDI-TOF MS technique was 93.3%. 16 isolates were not identified by MALDI-TOF MS but 16s rDNA sequencing identified them as , , and species. The most frequently identified species were: (13%), (12.5%), (12%) and (10%). Extended direct transfer method [2.26 ± 0.18 log (score)] in comparison to direct transfer method [2.15 ± 0.23 log (score)] improved spp.

Identification: Using a cut-off score of 1.7 was sufficient for accurate identification of species. MALDI-TOF MS identification scores for spp. decreased with longer incubation time. species predominantly were isolated from carcasses after skinning and evisceration steps in the slaughterhouse. MALDI-TOF MS could be an accurate way to identify species. Moreover, continuous improvement of the database and MALDI-TOF MS instrument enhance its performance in food control laboratories.