Identification of Food Spoilage Fungi Using MALDI-TOF MS: Spectral Database Development and Application to Species Complex

Diversity of spoilage microorganisms associated with fresh fruits and vegetables in French households

Food loss and waste generated throughout the food chain are major concerns in today's society. A high level of food waste occurs at the household's level and fresh fruit and vegetable (FFV) spoilage caused by microbial growth accounts for a large part of these losses. While numerous studies focused on spoilage microorganism diversity from primary production to distribution, little is known about those involved at the household level. In this context, this study aimed at investigating which FFV are usually wasted depending on the season and storage conditions at households, and identifying the microorganisms associated with spoiled FFV. During two periods (summer and autumn), 346 spoiled FFV samples were collected using a citizen science approach in 49 households in the Brest area (Finistère, Brittany, France). About three quarters of spoiled FFV collected originated from room temperature storage and 75 % were collected during summer. Among the studied samples, 75 % showed microbial growth after plating onto agar-based medium, and therefore, were likely spoiled because of microbial spoilage. Overall, 183 molds, 31 yeasts and 96 bacteria were isolated and identified using MALDI-TOF MS and sequencing. Among the 42 different mold species identified, Penicillium spp. were the most common representing more than 50 % of mold isolates followed by Botrytis (12.4 %), Mucor (8.6 %) and Cladosporium (7.6 %) spp. Hanseniaspora uvarum and Aureobasidium pullulans were the most prevalent yeast species while bacterial isolates showed the highest diversity of all identified organisms (49 species) with Pseudomonas spp., enterobacteria and lactic acid bacteria representing the most frequently isolated taxa. This study shows for the first time the microbial diversity associated with spoiled FFV of which a large proportion were stored at room temperature, suggesting that a better usage of FFV refrigeration could help reduce FFV waste in households.

Typing of clinical and reference strains of Saccharomyces cerevisiae using pulsed-field gel electrophoresis and MALDI-TOF MS

In recent years matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) has emerged as a rapid and reliable tool for microbial identification and diagnosis. However, its use for molecular typing of S. cerevisiae has been investigated in a limited number of studies, mainly based on brewing strains. The purpose of the study was to compare the results of the gold standard pulsed-field gel electrophoresis (PFGE) typing with MALDI-TOF MS on a subset of S. cerevisiae clinical and reference strains. The study comprised 50 clinical isolates, collected from single patients hospitalized in the Central Clinical Hospital of the Medical University of in Warsaw between 2014 and 2016. Furthermore eight reference strains i.e. three probiotic, four baker and one winery strains, were included. Strain typing was performed using PFGE and MALDI-TOF MS. PFGE split the study sample into six clusters and two unique profiles. Whereas MALDI-TOF MS typing produced five clusters. Overall, the results of PFGE and MALDI-TOF MS were congruent for all (49/50; 97%) but one clinical isolates. In both analyses, three probiotic strains, unlike baker's and winery strains, clustered only with clinical isolates. Although PFGE had a higher resolution capacity than MALDI-TOF MS, both methods allowed for a clear discrimination between clinically relevant (clinical & probiotic) and irrelevant (baker's and winery) strains. This is the first time that MALDI-TOF MS has proven useful in the epidemiological studies of S. cerevisiae.

Ethnic foods of Northeast India: insight into the light of food safety

BACKGROUND

Traditional and fermented foods are widely consumed by the ethnic population of Northeast India. These foods are not only very nutritious, easily available, and reasonably priced, but also boost immunity and protect from various seasonal infections and have been reported through several investigations. However, pathogens transmitted by these foods have never been reported. The process of preparation and preservation of fermented traditional foods involves various steps that can prompt contamination risks. Using the Indian Council of Medical Research (ICMR)-FoodNet surveillance data, we report the profile of enteric bacteria and mycotoxin-producing fungal pathogens identified in traditional and fermented food items and their importance in public health.

METHODS

Food samples were collected from rural areas of Assam, Arunachal Pradesh, Tripura, and Sikkim. Bacterial and fungal pathogens were tested as per the standard operating procedure at respective ICMR-FoodNet laboratories and MycoNet laboratory at Assam. Samples were collected under six broad categories: milk products, edible insects, non-vegetarian, legumes/cereals, veggies, and alcoholic beverages. Data compilation was done centrally through a digital data portal. Quality assurance was done by the ICMR-National Institute for Research in Bacterial Infections (NIRBI), Kolkata.

RESULT

A total of 1227 samples were collected, among which 78 samples (6.8%) were positive for enteric pathogens, with Bacillus cereus being the most prevalent one (n = 59). Furthermore, 71 fungal isolates were detected from different food categories. The most common mycotoxin-producing fungal genera include Aspergillus [A. fumigatus (n = 7)], Rhizopus [R. arrhizus (n = 13)], and Penicillium (n = 2).

CONCLUSION

Traditional foods have immense social, and cultural value and popularity among locals. However, processing, fermentation, and preservation of these foods without any preservatives and refrigerators, increases the possibility of contamination and growth by pathogenic organisms. It is crucial to understand the contamination risk involved during preparation so that the safety of these traditional foods can be ensured and local delicacies can be relished without any fear of foodborne infections and outbreaks, particularly when consumed by masses during festivals.