Microbial toxins in fermented foods: health implications and analytical techniques for detection

Occurrence, molecular characterization and tolerance of Cronobacter spp. isolated from fermented corn products in China

Cronobacter spp. is an opportunistic pathogen that cause serious infections in all age groups. The organism has frequently been isolated from plant-based foods, especially cereals. Therefore, this study determined the occurrence, molecular characterization and tolerance of Cronobacter in fermented corn products (FCP) in China. Isolates were speciated and genotyped according to multilocus sequence typing (MLST), which included the pathogenicity associated allele ompA, as well as serotyping. Twenty-two strains of Cronobacter (20 C. sakazakii and 2 C. muytjensii) were isolated from 216 FCP samples, such as fermented corn noodles, fermented corn doughs, fermented corn vermicelli, fermented corn flour paste, fermented corn beverage, and fermented corn bread. All Cronobacter isolates were divided into 8 sequence types (STs), 4 serotypes and 4 ompA genotypes. The dominant type (10/22) was C. sakzakii ST8, C. sakazakii serotypes O:2, and ompA5, mainly in fermented corn noodle and fermented corn dough. Of all the strains, Cronobacter strains with ST770 had a stronger ability to tolerate acid, osmotic stress and cold, while Cronobacter strains with ST8 had a weaker tolerance to acid, osmotic stress and cold. Eight isolates exhibited strong biofilm-forming ability (OD595 > 1), among which the ST770, ST771, and ST556 strains showed more pronounced abilities. All Cronobacter isolates were sensitive to amoxicillin/clavulanic acid, ceftazidime, aztreonam, meropenem, tetracycline, ciprofloxacin, trimethoprim/sulfamethoxazole, polymyxin B, and chloramphenicol, while 77.27% of isolates were resistant to cefotaxime. This study supports the concern of Cronobacter transmission through plant-based foods, and provides a theoretical basis for the prevention and control of this pathogen in FCP.

Pints of the past, flavours for the future

The recreation of historic beverages is possible via contemporary fermentations carried out with microbes revived form the past. Advanced molecular techniques have recently provided opportunities to investigate historic samples, such as those from beer found in shipwrecks, and provide data on their character as well as identifying differences with contemporary products. In some cases, isolates of yeasts and bacteria create the possibility for authentic recreations of fermented beverages that can have cultural and nostalgic interest. They may also provide insights into the relationship between humans and microbes. The authenticity of recreations, however, can be limited by difficulties in recipe interpretation, differences in water composition and ingredients, possible genetic changes of the retrieved microbes, and from advances in production processes and equipment. Such organisms may also be used to produce novel foods and for other new industrial (non-food) applications. Microorganisms in nature are known to survive geological time-periods. Nevertheless, the survival of some copiotrophic 'fermentation' microbes for a century or more suggests a robust stress biology. Moreover, it facilitates the exciting prospect of recreating fermented products once enjoyed by our predecessors.

In vitro co-culture of Clostridium scindens with primary human colonic epithelium protects the epithelium against Staphylococcus aureus

A complex and dynamic network of interactions exists between human gastrointestinal epithelium and intestinal microbiota. Therefore, comprehending intestinal microbe-epithelial cell interactions is critical for the understanding and treatment of intestinal diseases. Primary human colonic epithelial cells derived from a healthy human donor were co-cultured with Clostridium scindens (C. scindens), a probiotic obligate anaerobe; Staphylococcus aureus (S. aureus), a facultative anaerobe and intestinal pathogen; or both bacterial species in tandem. The co-culture hanging basket platform used for these experiments possessed walls of controlled oxygen (O2) permeability to support the formation of an O2 gradient across the intestinal epithelium using cellular O2 consumption, resulting in an anaerobic luminal and aerobic basal compartment. Both the colonic epithelial cells and C. scindens remained viable over 48 h during co-culture. In contrast, co-culture with S. aureus elicited significant damage to colonic epithelial cells within 24 h. To explore the influence of the intestinal pathogen on the epithelium in the presence of the probiotic bacteria, colonic epithelial cells were inoculated sequentially with the two bacterial species. Under these conditions, C. scindens was capable of repressing the production of S. aureus enterotoxin. Surprisingly, although C. scindens converted cholic acid to secondary bile acids in the luminal medium, the growth of S. aureus was not significantly inhibited. Nevertheless, this combination of probiotic and pathogenic bacteria was found to benefit the survival of the colonic epithelial cells compared with co-culture of the epithelial cells with S. aureus alone. This platform thus provides an easy-to-use and low-cost tool to study the interaction between intestinal bacteria and colonic cells in vitro to better understand the interplay of intestinal microbiota with human colonic epithelium.

Enhancing food safety in soybean fermentation through strategic implementation of starter cultures

Fermented soybean products have played a significant role in Asian diets for a long time. Due to their diverse flavours, nutritional benefits, and potential health-promoting properties, they have gained a huge popularity globally in recent years. Traditionally, soybean fermentation is conducted spontaneously, using microorganisms naturally present in the environment, or inoculating with traditional starter cultures. However, many potential health risks are associated with consumption of these traditionally fermented soybean products due to the presence of food pathogens, high levels of biogenic amines and mycotoxins. The use of starter culture technology in fermentation has been well-studied in recent years and confers significant advantages over traditional fermentation methods due to strict control of the microorganisms inoculated. This review provides a comprehensive review of microbial safety and health risks associated with consumption of traditional fermented soybean products, and how adopting starter culture technology can help mitigate these risks to ensure the safety of these products.

Recent Advances in the Detection of Food Toxins Using Mass Spectrometry

Edibles are the only source of nutrients and energy for humans. However, ingredients of edibles have undergone many physicochemical changes during preparation and storage. Aging, hydrolysis, oxidation, and rancidity are some of the major changes that not only change the native flavor, texture, and taste of food but also destroy the nutritive value and jeopardize public health. The major reasons for the production of harmful metabolites, chemicals, and toxins are poor processing, inappropriate storage, and microbial spoilage, which are lethal to consumers. In addition, the emergence of new pollutants has intensified the need for advanced and rapid food analysis techniques to detect such toxins. The issue with the detection of toxins in food samples is the nonvolatile nature and absence of detectable chromophores; hence, normal conventional techniques need additional derivatization. Mass spectrometry (MS) offers high sensitivity, selectivity, and capability to handle complex mixtures, making it an ideal analytical technique for the identification and quantification of food toxins. Recent technological advancements, such as high-resolution MS and tandem mass spectrometry (MS/MS), have significantly improved sensitivity, enabling the detection of food toxins at ultralow levels. Moreover, the emergence of ambient ionization techniques has facilitated rapid in situ analysis of samples with lower time and resources. Despite numerous advantages, the widespread adoption of MS in routine food safety monitoring faces certain challenges such as instrument cost, complexity, data analysis, and standardization of methods. Nevertheless, the continuous advancements in MS-technology and its integration with complementary techniques hold promising prospects for revolutionizing food safety monitoring. This review discusses the application of MS in detecting various food toxins including mycotoxins, marine biotoxins, and plant-derived toxins. It also explores the implementation of untargeted approaches, such as metabolomics and proteomics, for the discovery of novel and emerging food toxins, enhancing our understanding of potential hazards in the food supply chain.