Application of MALDI-TOF mass spectrometry for the assessment of prevalence of Listeria monocytogenes in raw milk, dairy products and freshwater fishes

Foodborne infections like Listeriosis cover several disorders and are a worldwide public health emergency. Listeria monocytogenes has been isolated from various foodstuffs, including milk and fishes. MALDI-TOF mass spectrometry technique is known for its rapid and accurate identification of bacterial organisms.

In the current research, a total of 360 samples comprising raw milk (130), milk products (125) and freshwater fishes (105) were screened for the detection of pathogenic Listeria species by using the USDA method. The recovered Listeria isolates were characterized using conventional set of biochemical analysis along with sugar fermentation tests and further confirmed by MALDI-TOF MS. The virulent nature of pathogenic Listeria isolates was also assessed by in vitro tests like hemolysis on blood agar, CAMP and PI-PLC assay.

In current study, on screening 360 animal origin food samples, three isolates were recovered from raw milk samples and identified as Listeria monocytogenes indicating an overall prevalence of Listeria monocytogenes to the tune of 0.83%. Excellent correlation was observed with identification of Listeria species using conventional phenotypic tests and advanced molecular tool Matrix Assisted Laser Desorption Ionization Time of Flight Mass Spectrometry (MALDI-TOF MS) technique. The results depict dependability of advanced technique for rapid and reliable identification of Listeria species.