Molecular identification of isolated fungi from unopened containers of greek yogurt by DNA sequencing of internal transcribed spacer region

Detection of Potential Microbial Contaminants and Their Toxins in Fermented Dairy Products: a Comprehensive Review

Fermented dairy products are dominant constituents of daily diets around the world due to their desired organoleptic properties, long shelf life, and high nutritional value. Probiotics are often incorporated into these products for their health and technological benefits. However, the safety and possible contamination of fermented dairy products during the manufacturing process could have significant deleterious health and economic impacts. Pathogenic microorganisms and toxins from different sources in fermented dairy products contribute to outbreaks and toxicity cases. Although the health and nutritional benefits of fermented dairy products have been extensively investigated, safety hazards due to contamination are relatively less explored. As a preventive measure, it is crucial to accurately identify and determine the associated microbiota or their toxins. It is noteworthy to highlight the importance of detecting not only the pathogenic microbiota but also their toxic metabolites so that putative outbreaks can thereby be prevented or detected even before they cause harmful effects to human health. In this context, this review focuses on describing techniques designed to detect potential contaminants; also, the advantages and disadvantages of these techniques were summarized. Moreover, this review compiles the most recent and efficient analytical methods for detecting microbial hazards and toxins in different fermented dairy products of different origins. Causative agents behind contamination incidences are also discussed briefly to aid in future prevention measures, as well as detection approaches and technologies employed. Such approach enables the elucidation of the best strategies to control contamination in fermented dairy product manufacturing processes.

Lactic Acid Bacteria as Biopreservation Against Spoilage Molds in Dairy Products - A Review

Mold spoilage of dairy products such as yogurt is a concern in dairy industry. Not only does it lead to substantial food waste, economic losses, and even brand image damage, but it may also cause public health concern due to the potential production of mycotoxin. Good hygiene practices are necessary to prevent contamination, but contamination may nevertheless occur at the production site and, not least, at the site of the consumer. In recent years, there has been a growing interest from consumers for "clean label" food products, which are natural, less-processed, and free of added, chemical preservatives, and a wish for shelf lives of considerable length in order to minimize food waste. This has sparked an interest in using lactic acid bacteria (LAB) or their metabolites as biopreservatives as a way to limit the growth of spoilage organisms in dairy products. A range of compounds produced by LAB with potential antifungal activity have been described as contributing factors to the inhibitory effect of LAB. More recently, growth inhibition effects caused by specific competitive exclusion have been elucidated. It has also become clear that the sensitivity toward both individual antifungal compounds and competition mechanisms differ among molds. In this review, the main spoilage molds encountered in dairy products are introduced, and an overview of the antifungal activity of LAB against different spoilage molds is presented including the main antifungal compounds derived from LAB cultures and the sensitivity of the spoilage molds observed toward these compounds. The recent findings of the role of competitive exclusion with emphasis on manganese depletion and the possible implications of this for biopreservation are described. Finally, some of the knowledge gaps, future challenges, and trends in the application of LAB biopreservation in dairy products are discussed.

Occurrence and diversity of waterborne fungi and associated mycotoxins in treated drinking water distribution system in South Africa: implications on water quality and public health

Despite increased public health concerns on the occurrences of potentially pathogenic/mycotoxigenic fungi in public drinking water system, dissemination of hygienically relevant fungi and their associated mycotoxins via distribution system under the dual burden of ageing infrastructure and ancillary distribution network lacking infrastructure for high-pressure water delivery systems is unknown. In this study, the diversity of fungi and occurrence of mycotoxins at 30 different points along treated piped water supply and ancillary distribution networks in Johannesburg, South Africa, were monitored for 12 months. Mycological analysis using cultural and molecular methods yielded 282 fungi belonging to phylum Ascomycota, having Aspergillus (91%), Penicillium (65%) and Trichoderma (31%) as dominant genera, with Aspergillus fumigatus, Penicillium citrinum, Purpureocillium lilacinum and Aspergillus flavus as the most prevalent species. Communal standpipe and reservoir outlets had significantly higher prevalence than other water samples. There was no strong correlation between total coliforms (r = 0.4266) and residual chlorine (r = - 0.1937), and fungal prevalence at p < 0.05. LC-MS/MS analysis detected aflatoxins B1, M1, G1 and G2 in 50, 9, 9 and 46% of water samples analysed, respectively, ranging between 0 and 3.18 ng/l. Deoxynivalenol (DON), 3-acetyl DON and 15-acetyl DON levels were between 8.4-96.1, 18.7-145.7 and 15.2-71.6 ng/l, respectively. However, the estimated average daily dose (ADD) for detected mycotoxins was below the tolerable daily intake (TDI), suggesting no toxicological risk. Presence of potentially mycotoxigenic fungi, despite the low toxicological risk, demonstrates a need for appropriate monitoring for fungi and mycotoxins in treated drinking water distribution systems for improved water quality and long-term public health assurance.

Prevalence and public health implications of mycotoxigenic fungi in treated drinking water systems

Insufficient potable water resources and poorly treated drinking water quality are the world's number one cause for preventable morbidity and mortality from water-related pathogenic microorganisms. Pathogenic microorganisms, including mycotoxigenic fungi, have been identified in treated drinking water. This paper presents a review of mycotoxigenic fungi as a health risk to the public as these fungi are responsible for allergies, cancers and opportunistic infections mainly to immunocompromised patients. The exacerbating factors contributing to fungal presence in water distribution systems, factors that lead to fungi being resistant to water treatment and treated drinking water quality legislations are also discussed. This paper provides a review on the prevalence of mycotoxigenic fungi and their implications to public health in treated drinking water, and the need for inclusion in treated drinking water quality regulations.

Multilocus Genetic Characterization of Lactobacillus fermentum Isolated from Ready-to-Eat Canned Food

The primary mission of the U.S. Food and Drug Administration is to enforce the Food, Drug, and Cosmetic Act and regulate food, drug, and cosmetic products. Thus, this agency monitors the presence of pathogenic microorganisms in these products, including canned foods, as one of the regulatory action criteria and also ensures that these products are safe for human consumption. This study was carried out to investigate the effectiveness of pathogen control and integrity of ready-to-eat canned food containing Black Bean Corn Poblano Salsa. A total of nine unopened and recalled canned glass jars from the same lot were examined initially by conventional microbiologic protocols that involved a two-step enrichment, followed by streaking on selective agar plates, for the presence of gram-positive and gram-negative bacteria. Of the eight subsamples examined for each sample, all subsamples of one of the containers were found positive for the presence of slow-growing rod-shaped, gram-positive, facultative anaerobic bacteria. The recovered isolates were subsequently sequenced at rRNA and gyrB loci. Afterward, multilocus sequence typing (MLST) was performed characterizing 11 additional known MLST loci (clpX, dnaA, dnaK, groEL, murC, murE, pepX, pyrG, recA, rpoB, and uvrC). Analyses of the nucleotide sequences of rRNA, gyrB, and 11 MLST loci confirmed these gram-positive bacteria recovered from canned food to be Lactobacillus fermentum . Thus, the DNA sequencing of housekeeping MLST genes can provide species identification of L. fermentum and can be used in the canned food monitoring program of public health importance.

Molecular Surveillance of Cronobacter spp. Isolated from a Wide Variety of Foods from 44 Different Countries by Sequence Typing of 16S rRNA, rpoB and O-Antigen Genes

Cronobacter spp. are emerging infectious bacteria that can cause acute meningitis and necrotizing enterocolitis in neonatal and immunocompromised individuals. Although this opportunistic human-pathogenic microorganism has been isolated from a wide variety of food and environmental samples, it has been primarily linked to foodborne outbreaks associated with powdered infant formula. The U.S. Food and Drug Administration use the presence of these microbes as one of the criteria to assess food adulteration and to implement regulatory actions. In this study, we have examined 195 aliquots of enrichments from the nine major categories of foods (including baby and medical food, dairy products, dried food, frozen food, pet food, produce, ready-to-eat snacks, seafood, and spices) from 44 countries using conventional microbiological and molecular techniques. The typical colonies of Cronobacter were then identified by VITEK2 and real-time PCR. Subsequently, sequence typing was performed on the 51 recovered Cronobacter isolates at the 16S rRNA, rpoB and seven O-antigen loci for species identification in order to accomplish an effective surveillance program for the control and prevention of foodborne illnesses.

Genetic Characterization of Cronobacter sakazakii Recovered from the Environmental Surveillance Samples During a Sporadic Case Investigation of Foodborne Illness

Cronobacter sakazakii is an opportunistic human-pathogenic bacterium known to cause acute meningitis and necrotizing enterocolitis in neonates and immunocompromised individuals. This human-pathogenic microorganism has been isolated from a variety of food and environmental samples, and has been also linked to foodborne outbreaks associated with powdered infant formula (PIF). The U.S. Food and Drug Administration have a policy of zero tolerance of these organisms in PIF. Thus, this agency utilizes the presence of these microorganisms as one of the criteria in implementing regulatory actions and assessing adulteration of food products of public health importance. In this study, we recovered two isolates of Cronobacter from the 91 environmental swab samples during an investigation of sporadic case of foodborne illness following conventional microbiological protocols. The isolated typical colonies were identified using VITEK2 and real-time PCR protocols. The recovered Cronobacter isolates were then characterized for species identification by sequencing the 16S rRNA locus. Further, multilocus sequence typing (MLST) was accomplished characterizing seven known C. sakazakii-specific MLST loci (atpD, fusA, glnS, gltB, gyrB, infB, and pps). Results of this study confirmed all of the recovered Cronobacter isolates from the environmental swab samples to be C. sakazakii. The MLST profile matched with the published profile of the complex 31 of C. sakazakii. Thus, rRNA and 7-loci MLST-based sequencing protocols are robust techniques for rapid detection and differentiation of Cronobacter species, and these molecular diagnostic tools can be used in implementing successful surveillance program and in the control and prevention of foodborne illness.