The COVID-19 pandemic has greatly impacted the U.S. food supply and consumer behavior. Food production and processing are being disrupted as illnesses, proactive quarantines, and government-mandated ...movement restrictions cause labor shortages. In this environment, the food industry has been required to adopt new, additional practices to minimize the risk of COVID-19 cases and outbreaks among its workforce. Successfully overcoming these challenges requires a comprehensive approach that addresses COVID-19 transmission both within and outside the facility. Possible interventions include strategies (i) to vaccinate employees, (ii) to assure that employees practice social distancing, (iii) to assure that employees wear face coverings, (iv) to screen employees for COVID-19, (v) to assure that employees practice frequent hand washing and avoid touching their faces, (vi) to clean frequently touched surfaces, and (vii) to assure proper ventilation. Compliance with these control strategies must be verified, and an overall COVID-19 control culture must be established to implement an effective program. Despite some public misperceptions about the health risk of severe acute respiratory syndrome coronavirus 2 on foods or food packaging, both the virus biology and epidemiological data clearly support a negligible risk of COVID-19 transmission through food and food packing. However, COVID-19 pandemic-related supply chain and workforce disruptions and the shift in resources to protect food industry employees from COVID-19 may increase the actual food safety risks. The goal of this review was to describe the COVID-19 mitigation practices adopted by the food industry and the potential impact of these practices and COVID-19-related disruptions on the industry's food safety mission. A review of these impacts is necessary to ensure that the food industry is prepared to maintain a safe and nutritious food supply in the face of future global disruptions.
Ropy defect of pasteurized fluid milk is a type of spoilage which manifests itself by an increased viscosity, slimy body, and string-like flow during pouring. This defect has, among other causes, ...been attributed to the growth, proliferation and exopolysaccharide production by coliform bacteria, which are most commonly introduced in milk as post-pasteurization contaminants. As we identified both Klebsiella pneumoniae ssp. pneumoniae and Rahnella inusitata that were linked to a ropy defect, the goal of this study was to characterize 3 K. pneumoniae ssp. pneumoniae strains and 2 R. inusitata for (1) their ability to grow and cause ropy defect in milk at 6°C and 21°C and to (2) probe the genetic basis for observed ropy phenotype. Although all K. pneumoniae ssp. pneumoniae and R. inusitata strains showed net growth of >4 log10 over 48 h in UHT milk at 21°C, only R. inusitata strains displayed growth during 28-d incubation period at 6°C (>6 log10). Two out of 3 K. pneumoniae ssp. pneumoniae strains were capable of causing the ropy defect in milk at 21°C, as supported by an increase in the viscosity of milk and string-like flow during pouring; these 2 strains were originally isolated from raw milk. Only one R. inusitata strains was able to cause the ropy defect in milk; this strain was able to cause the defect at both 6°C and 21°C, and was originally isolated from a pasteurized milk. These findings suggest that the potential of K. pneumoniae ssp. pneumoniae and R. inusitata to cause ropy defect in milk is a strain-dependent characteristic. Comparative genomics provided no definitive answer on genetic basis for the ropy phenotype. However, for K. pneumoniae ssp. pneumoniae, genes rffG, rffH, rfbD, and rfbC involved in biosynthesis and secretion of enterobacterial common antigen (ECA) could only be found in the 2 strains that produced ropy defect, and for R. inusitata a set of 2 glycosyltransferase- and flippase genes involved in nucleotide sugar biosynthesis and export could only be identified in the ropy strain. Although these results provide some initial information for potential markers for strains that can cause ropy milk, the relationship between genetic content and ropiness in milk remains poorly understood and merits further investigation.
Testing for coliforms has a long history in the dairy industry and has helped to identify raw milk and dairy products that may have been exposed to unsanitary conditions. Coliform standards are ...included in a number of regulatory documents (e.g., the U.S. Food and Drug Administration's Grade "A" Pasteurized Milk Ordinance). As a consequence, detection above a threshold of members of this method-defined, but diverse, group of bacteria can result in a wide range of regulatory outcomes. Coliforms are defined as aerobic or facultatively anaerobic, Gram negative, non-sporeforming rods capable of fermenting lactose to produce gas and acid within 48 h at 32-35°C; 19 genera currently include at least some strains that represent coliforms. Most bacterial genera that comprise the coliform group (e.g.,
,
, and
) are within the family Enterobacteriaceae, while at least one genus with strains recognized as coliforms,
, is in the family Aeromonadaceae. The presence of coliforms has long been thought to indicate fecal contamination, however, recent discoveries regarding this diverse group of bacteria indicates that only a fraction are fecal in origin, while the majority are environmental contaminants. In the US dairy industry in particular, testing for coliforms as indicators of unsanitary conditions and post-processing contamination is widespread. While coliforms are easily and rapidly detected, and are not found in pasteurized dairy products that have not been exposed to post-processing contamination, advances in knowledge of bacterial populations most commonly associated with post-processing contamination in dairy foods has led to questions regarding the utility of coliforms as indicators of unsanitary conditions for dairy products. For example,
spp. frequently contaminate dairy products after pasteurization, yet they are not detected by coliform tests. This review will address the role that coliforms play in raw and finished dairy products, their sources and the future of this diverse group as indicator organisms in dairy products.
Listeria monocytogenes continues to pose a food safety risk in ready‐to‐eat foods, including fresh and soft/semisoft cheeses. Despite L. monocytogenes being detected regularly along the cheese ...production continuum, variations in cheese style and intrinsic/extrinsic factors throughout the production process (e.g., pH, water activity, and temperature) affect the potential for L. monocytogenes survival and growth. As novel preservation strategies against the growth of L. monocytogenes in susceptible cheeses, researchers have investigated the use of various biocontrol strategies, including bacteriocins and bacteriocin‐producing cultures, bacteriophages, and competition with native microbiota. Bacteriocins produced by lactic acid bacteria (LAB) are of particular interest to the dairy industry since they are often effective against Gram‐positive organisms such as L. monocytogenes, and because many LAB are granted Generally Regarded as Safe (GRAS) status by global food safety authorities. Similarly, bacteriophages are also considered a safe form of biocontrol since they have high specificity for their target bacterium. Both bacteriocins and bacteriophages have shown success in reducing L. monocytogenes populations in cheeses in the short term, but regrowth of surviving cells can commonly occur in the finished cheeses. Competition with native microbiota, not mediated by bacteriocin production, has also shown potential to inhibit the growth of L. monocytogenes in cheeses, but the mechanisms are still unclear. Here, we have reviewed the current knowledge on the growth of L. monocytogenes in fresh and surface‐ripened soft and semisoft cheeses, as well as the various methods used for biocontrol of this common foodborne pathogen.
The various stages of the cheese-making process harbor distinct bacterial communities which may influence the sensory characteristics of artisanal cheeses. The objective of this study was to ...investigate the microbiota from dairy farm to final cheeses along an artisanal cheese-making continuum. Environmental and food samples were collected from 21 sites, including the dairy farm, milk, cheese plant, and finished cheeses. The microbiota of these samples were analyzed using 16S rRNA amplicon sequencing, with sequences grouped into operational taxonomic units (OTUs) by phylotype at the genus level. Alpha diversity decreased from dairy farm to finished cheese. Firmicutes was the dominant phylum, ranging from 31% to 92% between the dairy farm and finished cheeses, respectively, with Proteobacteria, Actinobacteria, and Bacteroides also present (25%, 11%, and 9% overall relative abundance, respectively). Of the 37 core OTUs (>5 reads in >80% of site replicates) observed in cheese, 32 were shared with the dairy farm. Starter-related genera (i.e., Lactococcus, Lactobacillus, Streptococcus, and Leuconostoc) represented between 69% and 98% relative abundance in final cheeses depending on style, with the remainder likely acquired from various environmental sources on the farm and during the cheese-making process.
•Farm-to-cheese 16S sequencing revealed differences in microbiota across processing stages.•Firmicutes was the most abundant phylum, followed by Proteobacteria.•Thirty-two of the 37 core OTUs in cheese were shared with the dairy farm.•Relative abundance of the starter-related genera was dependent on cheese style.•Dairy farm can be a potential source for non-starter genera in finished cheeses.
Bacteriocin(s) producing lactic acid bacteria naturally present in traditional cheeses represent an inexhaustive pool of microbes with safeguarding potential. Some bacteriocins produced by cheese ...lactic acid bacteria were already described as successful anti-staphylococcal agents. The presence of genes for bacteriocins with potential anti-staphylococcal activity was also demonstrated in two Slovenian traditional raw milk cheeses, “Tolminc” and “Kraški ovčji sir”. Same bacteriocin genes were also detected in viable lactic acid bacteria consortia’s isolated from “bacteriocin positive cheeses” on Rogosa, M17 and CATC agar media. The aim of the research was to elucidate whether or not this particular cheese consortia, in which bacteriocin genes were detected, actually exhibit anti-staphylococcal activity in milk and/or cheese. For this purpose different cheese consortia were selected in relation to versatility of detected bacteriocin genes and used to perform challenge tests against Staphylococcus aureus in milk and cheese. In milk following the time/temperature regime of traditional cheese production all cheese consortia effectively inhibited growth of Staphylococcus aureus in the range of app. 2 to 3 log. In cheese the inhibition of staphylococci was less pronounced but still evident since inhibition of app. 1.5 log was detected. Sole inhibition by lactic acid production was ruled out whilelinking inhibition directly to bacteriocin production would take some additional work.
The purpose of this research was to examine traditional Slovenian ‘Tolminc’ cheese for the presence of lactic acid bacteria that produce several bacteriocins. The presence of gene determinants for ...different bacteriocins in this type of cheese and in the cultivable population of ‘Tolminc’ microbiota, have already been demonstrated, as well as its antimicrobial activity. Due to the difficulties in connecting the presence of gene determinants for bacteriocins with the observed antimicrobial activity it was decided to examine in this study the same features on the level of individual bacteriocinogenic strains. Like in previous results, enterococci and their bacteriocins prevailed in cheese microbial consortia. None of isolated strains inhibited growth of Staphylococcus aureus, while the other indicator strains were inhibited in a strain specific manner. Most of isolated strains carried gene determinants for cytolysin. On the basis of gene determinants for bacteriocins, antimicrobial activity, phenotyping by PhP (PhenePlateTM) system and PCR identification, some similarities found were among Enterococcus isolates.
•A total of 13% of environmental sponge samples tested positive for Listeria.•Collecting sponges pre- vs. mid-operation yielded similar Listeria percent positives.•Five facilities showed Listeria ...persistence/re-introduction over >6 months.•Drains and floors were common sites where Listeria persistence was observed.
Small- and medium-sized dairy processing facilities (SMDFs) may face unique challenges with respect to controlling Listeria in their processing environments, e.g., due to limited resources. The aim of this study was to implement and evaluate environmental monitoring programs (EMPs) for Listeria control in eight SMDFs in a ∼1-year longitudinal study; this included a comparison of pre-operation (i.e., after cleaning and sanitation and prior to production) and mid-operation (i.e., at least 4 h into production) sampling strategies. Among 2,072 environmental sponge samples collected across all facilities, 272 (13%) were positive for Listeria. Listeria prevalence among pre- and mid-operation samples (15% and 17%, respectively), was not significantly different. Whole genome sequencing (WGS) performed on select isolates to characterize Listeria persistence patterns revealed repeated isolation of closely related Listeria isolates (i.e., ≤20 high-quality single nucleotide polymorphism hqSNP differences) in 5/8 facilities over >6 months, suggesting Listeria persistence and/or reintroduction was relatively common among the SMDFs evaluated here. WGS furthermore showed that for 41 sites where samples collected pre- and mid-operation were positive for Listeria, Listeria isolates obtained were highly related (i.e., ≤10 hqSNP differences), suggesting that pre-operation sampling alone may be sufficient and more effective for detecting sites of Listeria persistence. Importantly, our data also showed that only 1/8 of facilities showed a significant decrease in Listeria prevalence over 1 year, indicating continued challenges with Listeria control in at least some SMDFs. We conclude that options for simplified Listeria EMPs (e.g., with a focus on pre-operation sampling, which allows for more rapid identification of likely persistence sites) may be valuable for improved Listeria control in SMDFs.
•Eight genes of L. gasseri K7 A and B bacteriocins were expressed during growth.•Developed isolation protocol enabled efficient recovery of gassericin K7 B.•The active component of gassericin K7 B ...was verified at the proteomic level.•The isolated peptide showed a broad spectrum of antimicrobial activity.
The genome of Lactobacillus gasseri K7, isolated from baby's faeces, contains gene regions encoding two-component bacteriocins named gassericin K7 A (GenBank EF392861) and gassericin K7 B (GenBank AY307382). The strain has been known to exhibit bacteriocin activity in vitro, however, no data exist on the expression of particular genes of bacteriocins’ operons or on the activity of individual components of this bacteriocin complex, which has not been isolated so far. The objectives of this study were to examine bacteriocin genes’ expression during the growth of L. gasseri K7 and to isolate individual components in order to reveal the contribution of individual peptides to the overall bacteriocin activity. All eight target genes were expressed during exponential phase of growth in MRS broth. Mass spectrometry analysis revealed that the amino acid sequence of isolated peptide matched the deduced amino acid sequence of putative active peptide of gassericin K7 B (Gas K7 B_AcP) and GatX, a complementary peptide of gassericin T, previously supposed to have no antimicrobial activity. The isolated peptide showed a broad spectrum of antimicrobial activity. Furthermore, the isolation protocol developed in this study will enable to obtain a considerable amount of purified bacteriocins needed for further investigation of their functionality.
Fermentation and ripening specificity of traditional cheeses are predominantly directed by the natural microbial community present in milk selected by the cheese-making environment and technology. ...Therefore the traditional cheeses are unique products with specific microbiota biodiversity. There are several approaches for the identification of microbial population, however all of them have certain advantages and disadvantages. In this study the eligibility and performance of the Biolog phenotypic identification system (Biolog, Inc.) with GEN III microplates was tested. Parallel to this method, polymerase chain reaction with genus- and species-specific primers was performed. One hundred sixty-five isolates from nine types of artisan cheeses were isolated and analysed. Cheeses were produced from raw ewe’s milk in Slovenia, Bosnia and Herzegovina, Croatia and Serbia. The Biolog phenotypic identification system identified 90 isolates, but only 55 identifications acquired by the Biolog system were supported by polymerase chain reaction at a genus level and 28 at a species level. The obtained results showed that the reliability of commercial phenotypic identification systems was inadequate when analysing lactic acid bacteria isolates from natural, spontaneous fermentations and needs to be additionally corroborated by genotypic identification methods.
PDF
