Prevalence and phylogenetic traits of nitrite-producing bacteria in raw ingredients and processed baby foods: Potential sources of foodborne infant methemoglobinemia

Nitrite, which has been mainly regarded as a chemical hazard, can induce infant methemoglobinemia. As for nitrite as a product of microbial metabolism, the contribution of the oral or gut microbiome has mostly received attention, whereas the role of nitrite-producing bacteria (NPBs) in food has been less elucidated. In this study, mesophilic NPBs were isolated from food samples (n = 320) composed of raw ingredients for weaning foods (n = 160; beetroot, broccoli, carrot, lettuce, rice powder, spinach, sweet potato, and honey) and processed baby foods (n = 160; cereal snack, cheese, yogurt, powdered infant formula, sorghum syrup, vegetable fruit juice, and weaning food). The phylogenetic diversity of the NPB strains was analyzed via 16S rRNA sequencing. All 15 food items harbored NPBs, with a prevalence of 71.9 % and 34.4 % for the raw ingredients and processed foods, respectively. The NPBs isolated from the foods were identified as Actinomycetota (Actinomycetes), Bacteroidota (Flavobacteriia, Sphingobacteriia), Bacillota (Bacilli), or Pseudomonadota (Alpha-, Beta-, and Gammaproteobacteria). Among the raw and processed foods, beetroot (85.0 %) and powdered infant formula (70.0 %) showed had the highest NPB prevalence (P > 0.05). Bacillota predominated in both types of food. The contamination source of Pseudomonadota, which was another major phylum present in the raw ingredients, was presumed to be the soil and endophytes in the seeds, whereas that of Bacillota was the manufacturing equipment used with the raw ingredients. Common species for probiotics, such as Lacticaseibacillus, Leuconostoc, Enterococcus, and Bacillus, were isolated and identified as NPBs. To our knowledge, this is the first study to reveal the taxonomical diversity and omnipresence of NPBs in food for babies. The results of this study highlight the importance of food-mediated microbiological risks of infant methemoglobinemia which are yet underrecognized.

One Health approach for prioritization of potential foodborne pathogens: Risk-ranking, Delphi survey, and criteria evaluation pre- and post-COVID-19 pandemic

Frequent foodborne illnesses with unknown causative agents highlight the need to explore zoonotic potential foodborne pathogens (PFPs). An effective PFP prioritization tool is indispensable, especially after experiencing the recent pandemic caused by zoonotic SARS-CoV-2. Risk information on pathogens (excluding 30 known foodborne pathogens) provided by governmental and international organizations was reviewed to generate a list of PFPs. Risk-ranking of PFPs was conducted based on a literature review of food poisoning or detection cases, and the ranks were determined with a decision tree. PFPs were prioritized by infectious disease (ID), veterinary medicine (VET), and food safety (FS) experts through a pre- and postpandemic Delphi survey, and key criteria in their decisions were illuminated. Among 339 PFPs, 32 rank-1 PFPs were involved in the foodborne outbreak(s). Discrepancies in opinions on prioritization between experts in different fields deepened after the pandemic. Only VET and FS experts valued the plausibility of foodborne transmission in evaluating bacteria and viruses, and a significant correlation between their selection of PFPs was found (p < .05). The impact of the pandemic induced all fields to focus more on human transmission and severity/fatality in prioritizing viruses, and only FS experts emphasized the plausibility of foodborne transmission after the pandemic. In contrast to prioritizing bacteria or viruses, ID and VET experts are unusually focused on foodborne transmission when prioritizing parasites. Criteria of consensus deduced by interdisciplinary experts with different interests and the criteria directly related to foodborne transmission should be acknowledged for adequate PFP prioritization.

Cultivation-free sample preparation and DNA purification for direct real-time qPCR of intracellular or spore-like Coxiella burnetii in beef, goat, and lamb meat

Coxiella burnetii is a zoonotic pathogen that has been associated with foodborne outbreaks in products with ruminant origins. However, a method to detect C. burnetii in meat has been merely studied, and commercial kits cannot efficiently fulfill this purpose. In this study, an in-house preparation method for direct real-time qPCR of C. burnetii in beef, goat, and lamb meat was designed. In the sample preparation step (step 1), trypsin digestion and cell disruption techniques were introduced to target C. burnetii in an obligate intracellular or spore-like form. Afterward, 16 DNA purification protocols involving the following steps (steps 2-3) were assessed: the precipitation of meat proteins (step 2; using 2.5, 5.0 M NaCl or 1:1, 2:1 ethanol as the precipitant) and binding of DNA to silicon dioxide particles with chaotropic salts (step 3; using 2.5, 5.0 M NaCl or 2.5, 5.0 M guanidine thiocyanate as the salt). The protocols with superior performance in high-spiked loins (estimated 4-5 log cells/g) were verified in low-spiked (1-2 log cells/g) or Bacillus thuringiensis spore-inoculated (1-2 log CFU/g) loins, ribs, and hind legs. During the protein precipitation, 5.0 M NaCl induced significantly lower protein level as demonstrated by A280, when compared to 2.5 M NaCl or ethanol (P < 0.05). For the DNA binding step, Ct values were lowered in high-spiked goat or lamb loins (3.5-6.0▾; P < 0.05) when the concentration of NaCl was doubled or guanidine thiocyanate was introduced instead of NaCl as a chaotropic salt. Based on these results, two protocols using 5.0 M NaCl as the protein precipitant and 5.0 M NaCl (N2 + N2) or guanidine thiocyanate (N2 + G2) as the chaotropic salt were selected, which demonstrated successful detection in low-spiked (Ct values of N2 + N2, 32.9-35.6; N2 + G2, 32.3-36.4) or spore-inoculated meat (N2 + N2, 30.9-37.5; N2 + G2, 29.7-32.7). Verification in low-spiked meat showed that meat type/part significantly impacted the Ct values of N2 + G2 but not those of N2 + N2. To our knowledge, this is the first study that developed a highly accessible method for detecting C. burnetii in meat which could reveal the possibility of meat-borne Q fever in humans.

Microbial succession during button mushroom (Agaricus bisporus) production evaluated via high-throughput sequencing

Button mushrooms (Agaricus bisporus), are one of the most widely consumed mushrooms in the world. However, changes within its microbial community as it relates to the use of different raw materials and cultivation methods, as well as potential points of microbial contamination throughout the production process have not been investigated extensively. In the present study, button mushroom cultivation was investigated in each of the four stages (raw materials, composting (phase I, Ⅱ, and Ⅲ), casing, and harvesting), and samples (n = 186) from mushrooms and their related environments were collected from four distinct mushroom-growing farms (A-D) in Korea. Shifts within the bacterial consortium during mushroom production were characterized with 16 S rRNA amplicon sequencing. The succession of bacterial communities on each farm was dependent on the raw material incorporated, aeration, and the farm environment. The dominant phyla of the compost stack at the four farms were Pseudomonadota (56.7%) in farm A, Pseudomonadota (43.3%) in farm B, Bacteroidota (46.0%) in farm C, and Bacillota (62.8%) in farm D. During the Phase Ⅰ, highly heat-resistant microbes, such as those from the phylum Deinococcota (0.6-65.5%) and the families Bacillaceae (1.7-36.3%), Thermaceae (0.1-65.5%), and Limnochordaceae (0.3-30.5%) greatly proliferated. The microbial diversity within compost samples exhibited a marked decline as a result of the proliferation of thermophilic bacteria. In the spawning step, there were considerable increases in Xanthomonadaceae in the pasteurized composts of farms C and D - both of which employed an aeration system. In the harvesting phase, beta diversity correlated strongly between the casing soil layer and pre-harvest mushrooms, as well as between gloves and packaged mushrooms. The results suggest that gloves may be a major source of cross-contamination for packaged mushrooms, highlighting the need for enhanced hygienic practices during the harvesting phase to ensure product safety. These findings contribute to the current understanding of the influence of environmental and adjacent microbiomes on mushroom products to benefit the mushroom industry and relevant stakeholders by ensuring quality production.

Characterization of ready-to-eat fish surface as a potential source of contamination of Vibrio parahaemolyticus biofilms

The worldwide consumption of ready-to-eat seafood products has steadily increased due to a range of health benefits. However, depending on the handling or cutting process of raw fish, ready-to-eat sashimi can be exposed to microbiological risks that can lead to foodborne infection by marine pathogens. Since surface characteristics are key factors for microbial adhesion and biofilm formation, the present study aims to determine the correlation between raw fish skin properties and Vibrio parahaemolyticus biofilm formation. We analyzed V. parahaemolyticus biofilms (ATCC 17802; initially inoculated ca. 2 or 4 log CFU/cm²) on fish skin (gizzard shad, pomfret, red snapper, and mackerel; fish species served as sashimi without peeling the skin) formed under simulated marine environments (incubating in artificial seawater with rocking motion at 30 °C, the maximum temperature of seasonal seawater) for 24 h. The characteristics of fish skin were determined using confocal laser scanning microscopy/scanning electron microscopy. V. parahaemolyticus showed higher biofilm counts on fish skins than on stainless steel, which was used as a control (P < 0.05). In particular, V. parahaemolyticus formed biofilms with significantly higher levels of bacterial populations on gizzard shad and pomfret (ca. 5 log CFU/cm²; P < 0.05), highlighting the relationship between the biofilm formation level and the characteristics of gizzard shad and pomfret skins. The surface roughness of fish skins, including the main roughness parameters (Ra, Rq, and Rz), influenced the attachment of V. parahaemolyticus (P < 0.05). Additionally, images of V. parahaemolyticus biofilms suggested that different topographical profiles of fish species (e.g., mucus, unique structural features, etc.) could cause V. parahaemolyticus to exhibit different biofilm phenotypes, such as sticking to or entangling on the fish skin surface. The major findings of this study provide various phenotypic adhesions of V. parahaemolyticus to fish skin in considerations of the potential hazard for the consumption of ready-to-eat sashimi served with its skin.

Efficacy of combined caprylic acid and thymol treatments for inactivation of Listeria monocytogenes on enoki mushrooms in household and food-service establishments

Raw enoki mushroom is a high-risk vector for listeriosis, which led to foodborne outbreaks resulting in four deaths in the United States in 2020. This study aimed to investigate the washing method for the inactivation of L. monocytogenes in enoki mushrooms for household and food service establishments. Five methods of washing fresh agricultural products without using disinfectants were selected: (1) rinsing under running water (2 L/min, 10 min), (2-3) dipping in water (200 ml/20 g) at 22 or 40 °C for 10 min, and using (4) 10% NaCl or (5) 5% vinegar at 22 °C for 10 min. The antibacterial efficacy of each washing method along with the final rinse was tested with enoki mushrooms inoculated with a 3-strain cocktail of L. monocytogenes (ATCC 19111, 19115, 19117; ca. 6 log CFU/g). The 5% vinegar showed a significant difference in antibacterial effect compared to the other treatments except 10% NaCl (P < 0.05), with the maximum elimination of L. monocytogenes by 1.23 log CFU/g. Therefore, a disinfectant for enoki mushrooms that can complement the commonly used washing method was developed using antimicrobials (caprylic acid, CA: 0, 0.20, 0.40%; thymol, TM: 0, 0.075, 0.15%). By combined treatment of 0.40% CA and 0.15% TM at 22 °C for 10 min, L. monocytogenes was completely inactivated (>5.55 log reduction CFU/g) and did not recover after enrichment, although individual treatments of antimicrobials showed low bactericidal effects of <1.50 log reduction CFU/g. The bacterial membrane disintegration induced by the disinfectant was analyzed through flow cytometry. Additionally, the sensory scores (odor and appearance) and color parameters (L*, a*, and b*) of enoki mushrooms treated with the disinfectant were not significantly different from those of enoki mushrooms washed with water (P > 0.05). Our findings suggest a washing disinfectant consisting of low concentrations of CA and TM with synergistic antibacterial effects without quality deterioration that can ensure the safe consumption of raw enoki mushrooms in homes and food service establishments.

Consumer Trend of Using Ready-to-Use Salted Napa Cabbage at Home: Current Consumer Behaviors, Beliefs, and Opinions about the Main Ingredient of Kimchi

ABSTRACT

Salted napa cabbage is the most important ingredient of kimchi. Currently, people have started to prepare ready-to-use salted napa cabbage at home. This study focused on this trend by investigating consumers' beliefs, opinions, and actual use of the products by conducting a telephone survey (895 female consumers) and face-to-face interviews (n = 514) in 2016 and a telephone survey (n = 200) in 2021. Most respondents (93 and 91% in 2016 and 2021, respectively) answered that convenience was the main reason for using salted napa cabbage. Regarding consumption behavior, 22 and 16% of the respondents in each year used salted napa cabbage after storing it for more than 24 h. In particular, 85 and 91% of consumers stored the product at room temperature, and 60 and 58% used it without washing, which could affect the quality of the food, as microorganisms could multiply during the storage. Inappropriate handling increased by age group, especially in 2021 (P < 0.05). In the query on satisfaction after using the products, 85 and 80% of respondents were satisfied because the product was convenient (54%) and hygienic (17%). Conversely, the respondents who were not satisfied with the products did not like the degree of salting and unhygienic status of the products. The majority (93 and 80%) of consumers preferred buying salted napa cabbage again because of its convenience. Although consumers thought that hygiene and quality were important factors, many respondents (83 and 72%) were not aware of foodborne illnesses associated with kimchi. Nevertheless, consumers intended to pay more for safe, salted napa cabbage (72 and 76%). The results of this study provide useful and credible data for understanding the factors affecting consumers' consumption and general beliefs and opinions on the use of salted napa cabbage, especially for food safety management.

HIGHLIGHTS

Improvement of nested reverse transcription-polymerase chain reaction (RT-PCR) with high specificity and sensitivity detection of sapovirus in food matrix

Sapovirus (SaV) is a causative agent of human gastroenteritis in both community outbreaks and sporadic cases worldwide. Shellfish accumulate a variety of pathogens during filter feeding. In particular, the contamination of shellfish by SaV has caused several outbreaks. As reported previously, nested RT-PCR (nRT-PCR) has been widely used in clinical samples, but has not proven suitable for food samples, such as oysters. This study aimed to identify a primer set for the detection of SaV with high specificity and sensitivity in food samples. To accomplish this, primers were improved in RNA-dependent RNA polymerase (RdRp) regions of SaV whole genome sequences. The sensitivity of the improved nRT-PCR was 100-1000 times higher than that of previous nRT-PCR and > 10 times higher than that of the previous real-time RT-PCR assay. Notably, cross-reaction with other viruses or food matrices was not observed by the specificity test. This study improved the reliable primer set to detect SaV in various food matrices with high sensitivity.

Prevalence and phylogenetic analysis of human enteric emerging viruses in porcine stool samples in the Republic of Korea

Emerging infectious diseases (EID) in humans and animals are proving to be a serious health concern. This study investigated the prevalence of emerging or re-emerging human enteric viruses in porcine stools and swabs. Eleven enteric EID viruses were selected as target viruses for the current study and ranked based on their impact on public health and food safety: enterovirus (EV), hepatitis E virus, norovirus GI and GII, sapovirus (SaV), adenovirus (AdV), astrovirus, rotavirus, hepatitis A virus, aichivirus, and bocavirus. Using real-time RT-PCR or real-time PCR, EID viruses were detected in 129 (86.0%) of 150 samples. The most prevalent virus was EV, which was detected in 68.0% of samples, followed by AdV with a detection rate of 38.0%. In following sequencing and phylogenetic analyses, 33.0% (58/176) of the detected viruses were associated with human enteric EID viruses, including AdV-41, coxsackievirus-A2, echovirus-24, and SaV. Our results show that porcine stools frequently contain human enteric viruses, and that few porcine enteric viruses are genetically related to human enteric viruses. These findings suggest that enteric re-emerging or EID viruses could be zoonoses, and that continuous monitoring and further studies are needed to ensure an integrated “One Health” approach that aims to balance and optimize the health of humans, animals, and ecosystems.

Bacterial microbiota profiling of oyster mushrooms (Pleurotus ostreatus) based on cultivation methods and distribution channels using high-throughput sequencing

The annual consumption and production of oyster mushrooms (Pleurotus ostreatus) have continued to rise due to its nutritive and health-promoting benefits. Cultivated mushrooms are mostly grown in small to medium-scaled scale production plants that present hygienic challenges which could, in turn, increase associated foodborne pathogenic outbreaks. The present study aimed to investigate the shift in microbial ecologies of oyster mushrooms from pre-distribution (cultivation in bottles or on shelves) to post-distribution at supermarkets and open-air markets. Aerobic plate counts and coliforms were quantified using traditional microbiological techniques, and the microbiome associated with oyster mushrooms (n = 70) was analyzed using 16S rRNA amplicon sequencing for an enhanced level of bacterial microbiota profiling. Overall, coliforms recovered from pre-distribution bottle-cultivated mushrooms were 1.9 log CFU/g higher (p < 0.05) than that of shelf-cultivated mushrooms. The mean aerobic plate counts of oyster mushrooms distributed to open-air markets was 1.2 log CFU/g higher (p < 0.05) than packaged mushrooms from supermarkets while there were no significant differences in coliform counts. The pattern of bacterial composition differed by post-distribution channels, with oyster mushrooms collected from the open-air markets demonstrating the richest microbiome diversity. An increase in the relative abundance of Enterobacteriaceae (55-68 %) and Pseudomonadaceae (27-35 %) was observed in pre- and post-distribution mushrooms, respectively. However, no distinct bacterial microbiota differences were observed for the different cultivation methods or different geographical locations for each market type. The current findings add to our understanding of the effects of cultivation methods and commercial distribution channels regarding the microbiome of oyster mushrooms and may inform potential intervention strategies for future production and distribution processes. Furthermore, the tandem analyses of culture-dependent and culture-independent methods can provide more comprehensive information than that obtained when using each approach independently.

Pathogenicity and seasonal variation of Aeromonas hydrophila isolated from seafood and ready-to-eat sushi in South Korea

Aeromonas hydrophila is an emerging foodborne pathogen capable of causing human gastroenteritis, and the main reservoir is the aquatic environment. In this study, the prevalence and virulence of A. hydrophila in seafoods and ready-to-eat (RTE) sushi distributed in various conditions (refrigerated, dried, or frozen) or seasons was investigated. Strains were isolated from seafood (refrigerated or frozen oysters, sashimi, and processed fish; n = 333) and RTE sushi (n = 88) samples collected in South Korea and then genetically analyzed for gastroenteritis-related virulence genes (aer, ast, and alt). Raw oysters showed the highest prevalence of A. hydrophila (57.1%; 47/91) among all seafoods. Among the sashimi samples, flatfish sashimi (54.8%; 34/62) and salmon sushi (51.4%; 18/35) were the most prevalent. A. hydrophila was not detected in the oysters or anchovies distributed as either frozen or dried products. Seasonal investigations of sashimi and sushi showed that the summer prevalence of A. hydrophila with putative virulence genes was significantly lower in sashimi but highest in sushi. These results indicated that sushi could have been contaminated from several sources during the manufacturing or distribution processes. Significant correlations among the prevalence of putative virulence genes were confirmed, although no combination of genes presented a Phi correlation coefficient above 0.5 (0.26-0.43). To our knowledge, this is the first study to investigate the prevalence of A. hydrophila in various types of retail seafoods and RTE sushi in the East Asia region and then relate the prevalence to the distribution conditions of the samples. This study provides background information on the level of potential risk posed by A. hydrophila in retail seafoods and RTE sushi.

Contamination of Clostridium perfringens in soy sauce, and quantitative microbial risk assessment for C. perfringens through soy sauce consumption

The objective of this study was to conduct QMRA (quantitative microbial risk assessment) of Clostridium perfringens through soy sauce consumption. Four hundred and ninety soy sauce samples from markets were analyzed to detect C. perfringens. Temperature and time were also measured during transportation and display of soy sauce. A primary model was developed by fitting the Weibull model to the C. perfringens cell counts in soy sauce at 7-35°C, and δ (the time needed to decrease 1 log CFU/ml) and ρ (curve shape) were calculated. The parameters were analyzed, using the Exponential model (secondary model) as a function of temperature. The consumption amount and percentage of soy sauce were surveyed, and a dose-response model was searched. Using all collected data, a simulation model was prepared in the @RISK program to estimate the probability of C. perfringens foodborne illness by soy sauce consumption. C. perfringens were negative in 490 samples. Thus, the initial contamination level was estimated to be -2.9 log CFU/ml. The developed predictive models showed that C. perfringens cell counts decreased during transportation and display. The average consumption amounts, and the percentage of soy sauce were 7.81 ml and 81.2%, respectively. The simulation showed that the probability of C. perfringens foodborne illness by consumption of soy sauce was 1.7 × 10-16 per person per day. Therefore, the risk of C. perfringens by consumption of soy sauce is low in Korea.

Microbial ecology of alfalfa, radish, and rapeseed sprouts based on culture methods and 16S rRNA microbiome sequencing

Sprouts harbor high populations of bacteria and cause numerous foodborne disease outbreaks, yet little is known about their microbial composition. The present study aimed to define the microbiological ecology of sprouts using 16S rRNA microbiome sequencing and culture-dependent methods. Different types (radish, alfalfa, and rapeseed), brands (A, B, and C), and distribution routes (online and offline) of sprouts (n = 70) were considered for microbiome analysis, as well as quantitative (aerobic plate count and coliforms) and qualitative analyses (Escherichia coli O157:H7, Listeria monocytogenes, and Salmonella Typhimurium). The aerobic plate count ranged from 7 to 8 CFU/g, and the coliforms ranged from 6 to 7 log CFU/g. Microbiome analysis revealed that Proteobacteria was the dominant phylum, accounting for 79.0% in alfalfa sprouts, 68.5% in rapeseed sprouts, and 61.9% in radish sprouts. Enterobacteriaceae was the dominant family in alfalfa sprouts (33.9%) and rapeseed sprouts (14.6%), while Moraxellaceae (11.9%) were prevalent on radish sprouts. The majority of the dominant genera were common in the environment, such as soil or water. Alfalfa sprouts yielded the lowest aerobic plate count but the highest relative abundance of Enterobacteriaceae compared to the other sprouts. These results could explain why alfalfa sprouts are a leading cause of sprout-related foodborne disease outbreaks. Alpha-diversity results (Chao1 and Shannon indices) suggested that species richness was greater on radish sprouts than the other sprout types. Beta-diversity results showed samples were clustered by types, indicating dissimilarity in microbial communities. However, the distribution route had a limited influence on microbial composition. The present study provides a comparative examination of the microbial profiles of sprouts. Microbiome analyses contribute to an in-depth understanding of the microbial ecology of sprouts, leading to potential control measures for ensuring food safety.

Toxic potential of Bacillus cereus isolated from fermented alcoholic beverages

Pathogenicity of Bacillus cereus is associated with the production of various toxins. This study investigated the distribution of toxin genes encoding haemolysin BL (hblA, hblC, and hblD), nonhemolytic enterotoxin (nheA, nheB, and nheC), enterotoxin FM (entFM), cytotoxin K (cytK), and cereulide (ces) in 185 B. cereus strains isolated from draft beer, microbrewed beer, pasteurized beer, grape wine, other fruit wine, refined rice wine, traditional Korean pure liquor, and traditional Korean turbid rice wines. A total of 93.0% (172 isolates) of these isolates possessed at least one toxin gene. The nonhemolytic enterotoxin-encoding genes were highly prevalent in the isolates; the detection rate of enterotoxins was 91.4% for nheC, 81.6% for entFM, 62.7% for nheB, 57.3% for nheA, 53.0% for hblC, 48.6% for cytK, 36.8% for hblA, and 36.2% for hblD. Overall, 54.6% and 33.0% of strains carried the integrated Nhe-encoding gene cluster (nheA, nheB, nheC at the same time) and had the Hbl-encoding gene cluster, respectively. The cereulide synthetase gene was detected in only 2.2% of isolates. Toxin gene distribution patterns could be classified into 8 major profile clusters, and the most prevalent profile was the presence of enterotoxin genes only and no emetic toxin genes. Therefore, B. cereus in fermented alcoholic beverages was predominantly of the diarrhoeagenic type. Our results may provide important basic information when considering microbial standards and regulations for B. cereus in related products.

Recent Advances in the Application of Antibacterial Complexes Using Essential Oils

Although antibacterial spectrum of essential oils (EOs) has been analyzed along with consumers’ needs on natural biocides, singular treatments generally require high concentration of EOs and long-term exposures to eliminate target bacteria. To overcome these limitations, antibacterial complex has been developed and this review analyzed previous reports regarding the combined antibacterial effects of EOs. Since unexpectable combined effects (synergism or antagonism) can be derived from the treatment of antibacterial complex, synergistic and antagonistic combinations have been identified to improve the treatment efficiency and to avoid the overestimation of bactericidal efficacy, respectively. Although antibacterial mechanism of EOs is not yet clearly revealed, mode of action regarding synergistic effects especially for the elimination of pathogens by using low quantity of EOs with short-term exposure was reported. Whereas comprehensive analysis on previous literatures for EO-based disinfectant products implies that the composition of constituents in antibacterial complexes is variable and thus analyzing the impact of constituting substances (e.g., surfactant, emulsifier) on antibacterial effects is further needed. This review provides practical information regarding advances in the EO-based combined treatment technologies and highlights the importance of following researches on the interaction of constituents in antibacterial complex to clarify the mechanisms of antibacterial synergism and/or antagonism.

Risk factors influencing contamination of customized cosmetics made on-the-spot: Evidence from the national pilot project for public health

Customized cosmetics made by consumers or sellers on-the-spot have several safety issues, and therefore require a preventative approach to their safety management. The present study aimed to identify potential factors affecting the safety of customized cosmetics made on-the-spot. Heavy metals and microbial contaminants in customized cosmetics were analyzed in 120 samples. It was revealed that the transfer of cosmetics to new containers during the production process is a significant risk factor for cross-contamination and that heat treatment is crucial for reducing the number of microorganisms in the products. For instance, cosmetics made with heat and with no transfer showed relatively low microbial counts ranging from not detected to 440 CFU/ml. The high pH (>pH 10) of samples did not guarantee the microbial safety of the freshly made cosmetics (with a rinse-off product having 2,830 CFU/ml and a pH of 11.2). There was no significant difference in microbial counts among cosmetic types (P > 0.05); however, semisolid types, especially creams and rinse-off products, were susceptible to contamination (maximum 2,710 and 2,830 CFU/ml, respectively). Most microorganisms in the customized cosmetics (40.8%) decreased to non-detectable levels during 60 days of storage. None of the samples harbored heavy metals. Sequencing analysis of isolates revealed some bacteria and mold that could cause human infections. The results of this study suggest that the regulation of customized cosmetics should consider the risk factors revealed in this study, as the products made on-the-spot are also final products sent directly to consumers.

Health Functionality and Quality Control of Laver (Porphyra, Pyropia): Current Issues and Future Perspectives as an Edible Seaweed

The growing interest in laver as a food product and as a source of substances beneficial to health has led to global consumer demand for laver produced in a limited area of northeastern Asia. Here we review research into the benefits of laver consumption and discuss future perspectives on the improvement of laver product quality. Variation in nutritional/functional values among product types (raw and processed (dried, roasted, or seasoned) laver) makes product-specific nutritional analysis a prerequisite for accurate prediction of health benefits. The effects of drying, roasting, and seasoning on the contents of both beneficial and harmful substances highlight the importance of managing laver processing conditions. Most research into health benefits has focused on substances present at high concentrations in laver (porphyran, Vitamin B12, taurine), with assessment of the expected effects of laver consumption. Mitigation of chemical/microbiological risks and the adoption of novel technologies to exploit under-reported biochemical characteristics of lavers are suggested as key strategies for the further improvement of laver product quality. Comprehensive analysis of the literature regarding laver as a food product and as a source of biomedical compounds highlights the possibilities and challenges for application of laver products.

Synergistic staphylocidal interaction of benzoic acid derivatives (benzoic acid, 4-hydroxybenzoic acid and β-resorcylic acid) and capric acid: mechanism and verification study using artificial skin

Objectives

The present study was designed to investigate a synergistic staphylocidal interaction of antimicrobials.

Methods

The widely used preservative benzoic acid (BzA) and its derivatives [4-hydroxybenzoic acid (HA) and β-resorcylic acid (β-RA)] combined with capric acid (CPA) were investigated.

Results

β-RA was identified as the most effective antimicrobial exhibiting synergistic action with CPA against both Staphylococcus aureus and MRSA. For example, a complete reduction of bacteria (&gt;7.3 log reduction) was obtained within 5 min after treatment with 5.0 mM β-RA (0.079%) plus 0.20 mM CPA (0.004%), while treatment with each material individually showed low bactericidal effects (&lt;1.5 log reduction). Flow cytometry analysis identified membrane disruption related to the synergistic mechanisms, including the following: (i) membrane disruption by CPA (69.2% of cells were damaged by 0.20 mM CPA treatment); (ii) antimicrobial entry through the damaged membrane; and (iii) cytoplasmic ion imbalance resulting in cell death. We verified that the synergistic combination was also effective against MRSA on artificial skin (99.989% elimination after 5 min).

Conclusions

We used only consumer-preferred natural-borne antimicrobials and a very small amount of material was needed based on the synergistic effects. Therefore, these antimicrobials can be widely used as alternative anti-MRSA compounds in healthcare products, cosmetics, pharmaceutical products, foods and for environmental hygiene.

A risk assessment study of Bacillus cereus in packaged tofu at a retail market in Korea

The objective of the study was to conduct a quantitative microbial risk assessment of Bacillus cereus for packaged tofu in Korea. Packaged tofu, including soft and firm tofu from six retail markets in Korea, were monitored to determine the initial contamination level of B. cereus. Predictive growth and survival models were developed to predict the change in B. cereus populations as a function of time and temperature (4-45 °C) from market to home. B. cereus was detected in 11 (12.9%) samples among 85 samples purchased at retail markets, and the average contamination level was 1.84 log CFU/g. Growth of B. cereus in tofu was observed at a temperature above 11 °C. The probability risk of B. cereus diarrheal illness due to packaged tofu consumption at the retail market is 1.0 × 10^-4 per person per day. Key risk factors at the retail market and home are storage temperature and time of packaged tofu.

Short-Term Antifungal Treatments of Caprylic Acid with Carvacrol or Thymol Induce Synergistic 6-Log Reduction of Pathogenic Candida albicans by Cell Membrane Disruption and Efflux Pump Inhibition

BACKGROUND/AIMS

Although naturally-derived antifungals have been investigated for their ability to inactivate Candida albicans, which is a major cause of candidiasis, they have shown a less than 3 log reduction in C. albicans or required treatment times of longer than 3 h. Thus, the naturally-derived antifungals used in previous studies could not substantially eradicate C. albicans within a short period of time.

METHODS

To improve the fungicidal effects of naturallyderived antifungals against C. albicans within short time periods, we developed composites showing antifungal synergism using caprylic acid (CA), carvacrol (CAR) and thymol (THM) for 1-10 min at 22/37°C. Using flow cytometry, we examined the mode of action for the synergism of these compounds on membrane integrity and efflux pump activity.

RESULTS

Whereas the maximum reduction by individual treatments was 0.6 log CFU/ml, CA + CAR/THM (all 1.5 mM) eliminated all pathogens (> 6.8 log reduction) after 1 min at 37°C and after 10 min at 22°C. The flow cytometry results showed that exposure to CA damaged the membranes in 15.7-36.5% of cells and inhibited efflux pumps in 15.4-31.3% of cells. Treatments with CAR/THM slightly affected cell membranes (in 1.8-6.9% of cells) but damaged efflux pumps in 14.4-29.6% of cells. However, the combined treatments clearly disrupted membranes (> 83.1% of cells) and pumps (> 95.0% of cells). The mechanism of this synergism may involve membrane damage by CA, which facilitates the entry of antifungals into the cytoplasm, and the inhibition of efflux pumps by CA, CAR or THM, causing their accumulation within cells and, leading to cell death.

CONCLUSION

Antifungal composites (CA + CAR/THM) showing synergism (i.e., an additional 6 log reduction) within minutes at room/body temperature can be used to treat candidiasis and improve the microbiological safety of facilities contaminated with fungi as a novel alternative to synthetic antifungals.

Erratum to: Orally-Administered Bifidobacterium animalis subsp. lactis Strain BB12 on Dextran Sodium Sulfate-Induced Colitis in Mice

This erratum is being published to correct the author's contribution of above manuscript by Chae et al. that was published in Journal of Microbiology and Biotechnology (2018, 28:11, 1800-1805). The ninth author (Jin Hyup Lee) should be marked as corresponding author (*) with latest author (Young Jun Kim). The correspondence should appear as: *Corresponding authors Young Jun Kim Phone: +82-44-860-1435; Fax: +82-44-860-1586; E-mail: yk46@korea.ac.kr Jin Hyup Lee Phone: +82-44-860-1437 Fax: +82-44-860-1586; E-mail: jinhyuplee@korea.ac.kr.

Effects of Orally-Administered Bifidobacterium animalis subsp. lactis Strain BB12 on Dextran Sodium Sulfate-Induced Colitis in Mice

Inflammatory bowel disease, including Crohn's disease and ulcerative colitis (UC), is a chronically relapsing inflammatory disorder of the gastrointestinal tract. Intestinal epithelial cells (IECs) constitute barrier surfaces and play a critical role in maintaining gut health. Dysregulated immune responses and destruction of IECs disrupt intestinal balance. Dextran sodium sulfate (DSS) is the most widely used chemical for inducing colitis in animals, and its treatment induces colonic inflammation, acute diarrhea, and shortening of the intestine, with clinical and histological similarity to human UC. Current treatments for this inflammatory disorder have poor tolerability and insufficient therapeutic efficacy, and thus, alternative therapeutic approaches are required. Recently, dietary supplements with probiotics have emerged as promising interventions by alleviating disturbances in the indigenous microflora in UC. Thus, we hypothesized that the probiotic Bifidobacterium animalis subsp. lactis strain BB12 could protect against the development of colitis in a DSS-induced mouse model of UC. In the present study, oral administration of BB12 markedly ameliorated DSS-induced colitis, accompanied by reduced tumor necrosis factor-α-mediated IEC apoptosis. These findings indicate that the probiotic strain BB12 can alleviate DSS-induced colitis and suggest a novel mechanism of communication between probiotic microorganisms and intestinal epithelia, which increases intestinal cell survival by modulating pro-apoptotic cytokine expression.

Synergistic cranberry juice combinations with natural-borne antimicrobials for the eradication of uropathogenic Escherichia coli biofilm within a short time

Urinary tract infections (UTI), one of the most common diseases in humans, are caused primarily by uropathogenic Escherichia coli (UPEC). Cranberry juice (CB) is a widely known prophylaxis for UTI, but the treatment of CB alone could not effectively eradicate preformed UPEC biofilms. The aim of this study was to develop enforced CB composites within a short time by adding a small quantity of natural borne antimicrobials. UPEC biofilms (initial: 6·0 log CFU per cm² ), formed on silicone coupons in artificial urine medium, were exposed to CB (4-8%), caprylic acid (CAR; 0·025-0·05%) and thymol (TM; 0·025-0·05%) at 37°C for 1 min. Individual treatment of each compound did not show the significant antibacterial effect on UPEC biofilms (P > 0·05). Otherwise, the survivor counts of biofilms were synergistically reduced with CB containing any of the antimicrobials. For example combined treatment with CB (8%) + CAR (0·05%) + TM (0·05%) resulted in a 6 log reduction in UPEC populations in the biofilm (no detectable bacteria remained) with 4·6 log of synergistic bactericidal effect. The confocal laser scanning microscope images indicated that any composites including TM might result in biofilm detachment from the surface. The present method is cost-effective and more acceptable to consumers as it is based on the synergistic interaction of natural borne antimicrobials. The results of this study could be widely applicable in the functional food, medical and healthcare field. SIGNIFICANCE AND IMPACT OF THE STUDY: Anti-biofilm effect of cranberry juice (CB) has been focused mainly on inhibiting biofilm formation of uropathogenic Escherichia coli (UPEC); however, combined treatment with natural borne antimicrobials derived from coconut oil (caprylic acid) and oregano essential oil (thymol) could synergistically enhance its eradicating activity against biofilms. This study developed novel CB composites showing marked anti-biofilm effects (complete eradication of UPEC biofilms within just 1 min).

Novel Antibiotic Testing Approaches Reveal Reduced Antibiotic Efficacy Against Shiga Toxin-Producing Escherichia coli O157:H7 Under Simulated Microgravity

As a foodborne and environmental pathogen, Shiga toxin-producing Escherichia coli O157:H7 could pose a health threat to immunocompromised astronauts during a space mission. In this study, novel approaches, including real-time testing and direct evaluation of resistance mechanisms, were used to evaluate antibiotic efficacy against E. coli O157:H7 under low-shear modeled microgravity (LSMMG) produced using a rotary cell culture system. When compared with normal gravity (NG), bacterial growth was increased under LSMMG in the presence of sub-inhibitory nalidixic acid concentrations and there was an accompanying up-regulation of stress-related genes. LSMMG also induced transcriptional changes of the virulence genes stx1 and stx2, highlighting the potential risk of inappropriate antibiotic use during a spaceflight. The degree of bacterial cell damage induced by the antibiotics was reduced under LSMMG, suggesting low induction of reactive oxygen species. Efflux pumps were also shown to play an important role in these responses. Increased cell filamentation was observed under LSMMG upon ampicillin treatment, possibly reflecting a protective mechanism against exposure to antibiotics. These observations indicate that, in the presence of antibiotics, the survival of E. coli O157:H7 is greater under LSMMG than under NG, indicating that antibiotic therapies may need to be adjusted during space missions.

Underrecognized niche of spore-forming bacilli as a nitrite-producer isolated from the processing lines and end-products of powdered infant formula

Although nitrite in powdered milk formula (PIF) is a recognized health risk for infants, the presence of nitrite in PIF has only been investigated as a chemical contaminant during the inspection of end-products. The risk posed by microbial sources of nitrite during the PIF manufacturing process has not been considered. This is the first study to report the taxonomy and physiological characteristics of nitrite-producing bacteria isolated from PIF processing environments. All isolates identified as nitrite-producers (133 out of 501 strains collected over four years) from work-in-process and end-products of PIF were spore-forming bacilli. Nitrite-producing metabolism under PIF processing conditions was found in not only thermophilic isolates (3 Bacillus, 60 Geobacillus from 63 strains; 100%) but also in mesophilic isolates (65 Bacillus, 1 Anoxybacillus from 70 strains; 65.7%). Geobacillus was the only highly heat-resistant sporeformer and vigorous nitrite-producer exhibiting dramatic increases in nitrite over short periods of incubation (a maximum value within 3 h). High conversions of nitrate to nitrite (up to 88.8%) was also observed, highlighting bacteria as a key source of nitrite in PIF processing lines. Further research into the diversity of metabolic activity observed in this study can facilitate specialized management of nitrite-producers in PIF processing lines.

Optimization of spray drying parameters and food additives to reduce glycation using response surface methodology in powdered infant formulas

The heat-based spray drying process generating the highest level of advanced glycation end-products (AGEs) in the infant formula processing was set as a control point from which the levels of AGE markers, N-carboxymethyllysine, 5-hydroxymethylfurfural, and fluorescence intensity, can be mitigated. We optimized the parameters, including inlet temperature, feeding rate, and aspirator rate during spray drying, and alternatively optimized food additives, including pyridoxine hydrochloride, dl-α-tocopheryl acetate, and l-carnitine. Using response surface methodology, the optimal condition based on our experimental condition for the inlet temperature, pump rate, and aspirator rate were 148.7 °C, 342.4 mL/h and 28.6 m³/h, respectively, and the optimal conditions of pyridoxine hydrochloride, dl-α-tocopheryl acetate and l-carnitine were 0.99 mg/100 g dry mass (DM), 8 mg/100 g DM and 20.4 mg/100 g DM, respectively. These results suggest that AGEs can be mitigated by controlling the parameters and optimizing the addition of food additives during the spray-drying process.

Factors Affecting Microbiological Quality of Vegetable- and Meat-Based Meals Served at Cafeterias in the Republic of Korea

A total of 364 samples of vegetable- and meat-based meals were collected at three processing steps: step I, preparation of raw ingredients; step II, processing and cooking; and step III, finished meals. Microbiological quality was evaluated by using data for the prevalence and concentration of the aerobic plate counts, total coliforms (TC), fecal coliforms (FC), and Escherichia coli. The data were analyzed for differences between cafeterias, seasons, raw materials, and processing steps. Fourteen (15.2%) of the 92 finished meal samples were microbiologically unsatisfactory. Neither cafeteria nor season was significantly associated with microbiological quality ( P > 0.05). However, the type of raw ingredients and processing steps were significantly associated with differences in microbiological quality. Vegetable-based meals had higher TC concentrations than meat-based meals because salad and seasoned and fermented vegetables are not cooked, unlike heat-processed meat products. Microbial counts tended to decrease through the processing steps, and E. coli, which could only be enumerated on uncooked chicken breast (1.6 log CFU/g) and sliced pork (2.6 log CFU/g), was totally eliminated by boiling and roasting. However, the presence of FC was not completely eliminated, even by cooking, and so this group of organisms should be considered as an important indicator of hygienic meal preparation in cafeterias. Although pathogenic E. coli was not isolated in this study, continuous microbiological monitoring of composite foods served in cafeterias should be performed as the presence of TC and FC in finished meals indicates the potential for contamination by pathogenic E. coli.

Microbial diversities and potential hazards of Korean turbid rice wines (makgeolli): Multivariate analyses

A number of makgeolli (Korean traditional turbid rice wine) products are commercially available in various forms. To date, there has been no comprehensive investigation of these products. Here, we collected samples of almost all of the makgeolli products that are currently commercially available (n = 167), recorded their manufacturing variables, and examined physiochemical parameters and microbial communities, using quantitative and qualitative methods. The aerobic plate count (APC) and counts of lactic acid bacteria (LAB), acetic acid bacteria (AAB), fungi, total coliforms, and Bacillus cereus were obtained, and the presence of Escherichia coli and eight foodborne pathogens was also examined. The data obtained were segmented and analyzed based on multiple variables associated with the manufacturing characteristics. Despite high ethanol contents (up to 16.0%) and high acidities (pH 3.3-4.5), the rice wine products examined here had diverse and abundant microbiotas (mean values: APC, 5.3; LAB,4.4; AAB,1.5; fungi, 3.8 log CFU/ml). In particular, LAB and fungi, which are used as co-starter cultures during rice wine manufacturing, accounted for the majority of the microbiotas. Bivariate analyses revealed significant positive correlations between the individual micro-organism counts (Pearson correlation coefficient = 0.668-0.947). Among the manufacturing variables considered in this study, only the pasteurization status had a significant effect on the microbial communities of rice wine products (p < 0.05). When examining the presence of foodborne pathogens, B. cereus was isolated from some of the rice wine products (58.1%) at low levels (<100 CFU/ml), and its detection rate was not significantly lower in the pasteurized products than the raw products. Overall, the results presented here provide a comprehensive overview of the microbiotas of commercially available turbid rice wines and their relationships to manufacturing variables. These data will help to direct future studies focusing on rice wine quality and safety control measures.

Response surface modeling of reductions in uropathogenic Escherichia coli biofilms on silicone by cranberry extract, caprylic acid, and thymol

A response surface methodology was used to build a model to predict reductions in uropathogenic Escherichia coli biofilms in response to three compounds: cranberry extract [CB] at 3.0-9.0%, and caprylic acid [CAR] and thymol [TM] at 0.01%-0.05%. The predictive model for microbial reduction had a high regression coefficient (R² = 0.9988), and the accuracy of the model was verified (R² = 0.9527). Values of CAR, TM, and the quadratic term CAR² were the most significant (P < 0.0001) for bacterial reduction. Interactions between CB and CAR, and TM and CB, also affected bacterial reduction. The optimum conditions (a 5.8 log₁₀ reduction) determined by ridge analysis were 8.3% CB +0.04% CAR +0.04% TM at 37 °C for 1 min. The model could be used to predict the most cost-efficient amounts of antimicrobial agents for anti-urinary tract infection products such as catheter lock solution and antimicrobial coatings for catheters.

Citrus fruit extracts with carvacrol and thymol eliminated 7-log acid-adapted Escherichia coli O157:H7, Salmonella typhimurium, and Listeria monocytogenes: A potential of effective natural antibacterial agents

Despite the widespread belief that citrus fruit extracts (CFEs) are microbiologically safe due to their acidity, limited bactericidal effect results in low applicability as antibacterial agent and outbreaks occurred by acid-adapted pathogens. Here, we examined the antibacterial effects of CFEs [lime (Citrus medica), lemon (Citrus limon), calamansi (Citrus microcarpa)] combined with essential oil components (EOCs; carvacrol and thymol) against non-acid-adapted/acid-adapted Escherichia coli O157:H7, Salmonella Typhimurium, and Listeria monocytogenes under 22 °C for 5 min. CFEs (<20%) alone or small amounts of EOCs (2.0 mM; 0.032%) alone could not inactivate the target bacteria effectively. However, combined treatments exhibited marked synergy: CFE + EOCs eliminated all the bacteria (>6.9 log CFU/ml). Among the CFEs tested, the highest synergism was shown by calamansi, an exotic citrus fruit previously unrecognized as an antibacterial agent. Although acid-adaptation improved bacterial survival, calamansi (<20%) + EOCs (<0.032%) completely inactivated even the most resistant pathogen (E. coli O157:H7). Validation test also showed that all tested commercial juice products also eliminated acid-adapted pathogens when used with EOCs. Physicochemical analysis of tested CFEs (pH measurement and HPLC analysis of components) revealed that low pH and flavanone (hesperidin) did not contribute to the synergistic bactericidal effects. Rather, the high citric acid content is likely to contribute to the strong synergistic effect with EOCs by damaging susceptible bacterial membranes. Sensory scores for CFEs were not altered by addition of EOCs at concentrations up to 1.5 mM. This study provides new insight into the utility of CFEs with EOCs to improve not only the microbiological safety of food products containing CFEs but also their applicability as natural antibacterial complex.

Microbiological criteria and ecology of commercially available processed cheeses according to the product specification and physicochemical characteristics

Although global cheese manufacturers release a variety of products onto the market, research on the microbiological quality and safety of cheese has focused mainly on conventional cheeses made from milk. Here, this study aimed to investigate commercially processed cheese products produced by mixing conventional cheeses after melting. Two approaches were used: a summary and comparison of legal definitions and standards/regulations regarding the microbiological criteria used by major cheese traders in the global market (Australia/New Zealand, China, European Union, Japan, Mexico, Republic of Korea, and the United States) and a comprehensive microbiological analysis of commercial products (n = 800), along with an assessment of salinity, pH, water activity, and heating conditions. The results of the literature search showed that major importing countries (China, Japan, Mexico, and the Republic of Korea) have stricter microbiological criteria for commercially available cheese products than major exporters (Australia/New Zealand, EU, and the USA). The former set limits with respect to the number of total coliforms in the product. Microbiological analyses were designed according to global standards and recommendations. No test sample contained detectable levels of Clostridium perfringens, enterohemorrhagic Escherichia coli, Listeria monocytogenes, Salmonella, or Staphylococcus aureus. In addition, no coliform bacteria (including E. coli) were detected. Overall, 79.9% of the samples contained detectable aerobic plate counts (1.0-7.8 log CFU/g); these levels varied significantly according to product type (grated cheese > chunks; cream cheese > portions or sliced) (p < .05). There was no significant association between microbe levels and salinity, water activity, pH, and heating conditions. The results can be used to develop a comprehensive database about commercially processed cheese products available in the global market and, as such, may be helpful for both national authorities and cheese manufacturers when considering novel strategic management plans for microbiological quality and safety.

Sodium Chloride Does Not Ensure Microbiological Safety of Foods: Cases and Solutions

Addition of salt or salt-containing water to food is one of the oldest and most effective preservation methods in history; indeed, salt-cured foods are generally recognized as microbiologically safe due to their high salinity. However, a number of microbiological risks remain. The microbiological hazards and risks associated with salt-cured foods must be addressed more in-depth as they are likely to be underestimated by previous studies. This review examined a number of scientific reports and articles about the microbiological safety of salt-cured foods, which included salted, brined, pickled, and/or marinated vegetables, meat, and seafood. The following subjects are covered in order: (1) clinical cases and outbreaks attributed to salt-cured foods; (2) the prevalence of foodborne pathogens in such foods; (3) the molecular, physiological, and virulent responses of the pathogens to the presence of NaCl in both laboratory media and food matrices; (4) the survival and fate of microorganisms in salt-cured foods (in the presence/absence of additional processes); and (5) the interaction between NaCl and other stressors in food processes (e.g., acidification, antimicrobials, drying, and heating). The review provides a comprehensive overview of potentially hazardous pathogens associated with salt-cured foods and suggests further research into effective intervention techniques that will reduce their levels in the food chain.

Changes in microbial composition and the prevalence of foodborne pathogens in crab marinated in soy sauce produced by six manufacturing plants

BACKGROUND

The present study examined the changes in microbiological composition during the production process of crab marinated in soy sauce, potential microbial hazards, potential contamination routes and effective critical control points. Crab and soy sauce samples were obtained from six different manufacturing plants at different stages, and their microbiological content was comprehensively assessed by quantitative and qualitative analyses.

RESULTS

The results revealed the following: (1) the final products contained 4.0 log colony-forming units (CFU) g^-1 aerobic plate counts (APCs) and 1.1 log CFU g^-1 coliforms, which may have been introduced from the raw materials (the level of APCs in raw crab and soy sauce mixed with other ingredients was 3.8 log CFU g^-1 and 4.0 log CFU mL^-1 respectively); (2) marination of crab in soy sauce may allow cross-contamination by coliforms; (3) only Bacillus cereus and Staphylococcus aureus were qualitatively detected in samples at different stages of manufacture (detection rate of 28 and 5.6% respectively), and these bacteria may impact the microbiological quality and safety of crab marinated in soy sauce; and (4) bacterial counts were either maintained or increased during the manufacturing process (suggesting that no particular step can be targeted to reduce bacterial counts).

CONCLUSION

Proper management of raw materials and the marination process are effective critical control points, and alternative interventions may be needed to control bacterial quantity. The results provide important basic information about the production of crab marinated in soy sauce and may facilitate effective implementation of sanitary management practices in related industries and research fields. © 2016 Society of Chemical Industry.

Current Interventions for Controlling Pathogenic Escherichia coli

This review examined scientific reports and articles published from 2007 to 2016 regarding the major environmental sources of pathogenic Escherichia coli and the routes by which they enter the human gastrointestinal tract. The literature describes novel techniques used to combat pathogenic E. coli transmitted to humans from livestock and agricultural products, food-contact surfaces in processing environments, and food products themselves. Although prevention before contamination is always the best "intervention," many studies aim to identify novel chemical, physical, and biological techniques that inactivate or eliminate pathogenic E. coli cells from breeding livestock, growing crops, and manufactured food products. Such intervention strategies target each stage of the food chain from the perspective of "Farm to Table food safety" and aim to manage major reservoirs of pathogenic E. coli throughout the entire process. Issues related to, and recent trends in, food production must address not only the safety of the food itself but also the safety of those who consume it. Thus, research aims to discover new "natural" antimicrobial agents and to develop "multiple hurdle technology" or other novel technologies that preserve food quality. In addition, this review examines the practical application of recent technologies from the perspective of product quality and safety. It provides comprehensive insight into intervention measures used to ensure food safety, specifically those aimed at pathogenic E. coli.

Raw ready-to-eat seafood safety: microbiological quality of the various seafood species available in fishery, hyper and online markets

Microbiological quality of 206 raw ready-to-eat seafood samples was investigated according to species (gizzard shad, halibut, rockfish, tuna, oyster and squid) and distribution channels (fishery, hyper and online market). Enumeration of aerobic plate count and total coliforms (TC) and pathogenic bacteria (Bacillus cereus, Staphylococcus aureus and Vibrio parahaemolyticus) was performed, and level of microbiological quality was classified into four groups: satisfactory, acceptable, unsatisfactory and unacceptable. Qualitative analysis was also performed for Escherichia coli and eight foodborne pathogens (B. cereus, E. coli O157:H7, Listeria monocytogenes, Salmonella spp., S. aureus, Vibrio cholerae, V. parahaemolyticus, and Vibrio vulnificus). Raw ready-to-eat seafood products revealed 0·5% at an unsatisfactory level and 4·9% at an unacceptable level due to ≥4 log CFU g^-1 of TC in squid and ≥3 log CFU g^-1 of V. parahaemolyticus in gizzard shad respectively. Gizzard shad was shown to be potentially hazardous, as its sashimi is eaten with its skin attached. Bacillus cereus, E. coli, S. aureus, V. parahaemolyticus and V. vulnificus were qualitatively detected. Samples from the fishery market showed higher detection rate especially in V. parahaemolyticus (21·6%) and V. vulnificus (1·7%) which indicates the need to improve microbiological safety of raw ready-to-eat seafood products in fishery market.

SIGNIFICANCE AND IMPACT OF THE STUDY

Raw ready-to-eat seafood products like sashimi can be easily contaminated with various bacteria from aquatic environments and human reservoirs, which subsequently bring about a risk in food poisoning due to no heating process before consumption. The results of this study provide comprehensive microbiological data on various species of raw ready-to-eat seafood from various distribution channels. It may contribute to establish reasonable standard and effective strategies to ensure a good microbiological quality of raw ready-to-eat seafood for the safety of meals, like sashimi and sushi.

Microbicidal effects of plain soap vs triclocarban-based antibacterial soap

The aim of this study was to determine the bactericidal effects of plain and antibacterial soap. The bactericidal effects of plain and antibacterial soap containing 0.3% triclocarban were examined against 10 Gram-positive and 10 Gram-negative bacterial strains after exposure at 22°C and 40°C for 20 s. Gram-negative bacteria were more susceptible to both soaps than Gram-positive bacteria. However, with one exception (Enterococcus faecalis ATCC 19433 at 40°C), there was no significant difference between the effects of medicated and non-medicated soap at either temperature. Triclocarban in soap does not lead to a meaningful reduction in bacterial levels during use.

Destruction of Bacillus cereus spores in a thick soy bean paste (doenjang) by continuous ohmic heating with five sequential electrodes

This study selected spores from Bacillus cereus FSP-2 strain (the isolate from a commercial doenjang processing line) as the test strain which showed significantly higher thermal resistance (P < 0·05) than B. cereus reference strain (ATCC 27348). The spores in doenjang were subjected to ohmic heating (OH) at 95, 105, 115 and 125°C for 30, 60 or 90 s using a five sequential electrode system (electrical field: 26·7 V cm(-1) ; alternating current frequency: 25 kHz). OH at 105°C for 30-90 s reduced the B. cereus spore count in doenjang samples to <4 log CFU g(-1) . Since OH treatment at 115 and 125°C caused a perceivable colour change in the product (>1·5 National Bureau of Standards units), treatment at 105°C for 60 s was selected and applied on a large scale (500 kg of product). Reliable and reproducible destruction of B. cereus spores occurred; the reductions achieved (to < 4 log CFU g(-1) ) met the Korean national standards. Scanning electron microscopy revealed microstructural alterations in the spores (shrinkage and a distorted outer spore coat). OH is an effective method for destroying B. cereus spores to ensure the microbiological quality and safety of a thick, highly viscous sauce.

SIGNIFICANCE AND IMPACT OF THE STUDY

This study shows that an ohmic heating (OH) using a five sequential electrode system can effectively destroy highly heat-resistant Bacillus cereus spores which have been frequently found in a commercial doenjang processing line without perceivable quality change in the product. In addition, it may demonstrate high potential of the unique OH system used in this study that will further contribute to ensure microbiological quality and safety of crude sauces containing high levels of electrolyte other than doenjang as well.

Phytic Acid and Sodium Chloride Show Marked Synergistic Bactericidal Effects against Nonadapted and Acid-Adapted Escherichia coli O157:H7 Strains

The synergistic antimicrobial effects of phytic acid (PA), a natural extract from rice bran, plus sodium chloride against Escherichia coli O157:H7 were examined. Exposure to NaCl alone at concentrations up to 36% (wt/wt) for 5 min did not reduce bacterial populations. The bactericidal effects of PA alone were much greater than those of other organic acids (acetic, citric, lactic, and malic acids) under the same experimental conditions (P < 0.05). Combining PA and NaCl under conditions that yielded negligible effects when each was used alone led to marked synergistic effects. For example, whereas 0.4% PA or 3 or 4% NaCl alone had little or no effect on cell viability, combining the two completely inactivated both nonadapted and acid-adapted cells, reducing their numbers to unrecoverable levels (>7-log CFU/ml reduction). Flow cytometry confirmed that PA disrupted the cell membrane to a greater extent than did other organic acids, although the cells remained viable. The combination of PA and NaCl induced complete disintegration of the cell membrane. By comparison, none of the other organic acids acted synergistically with NaCl, and neither did NaCl-HCl solutions at the same pH values as the test solutions of PA plus NaCl. These results suggest that PA has great potential as an effective bacterial membrane-permeabilizing agent, and we show that the combination is a promising alternative to conventional chemical disinfectants. These findings provide new insight into the utility of natural compounds as novel antimicrobial agents and increase our understanding of the mechanisms underlying the antibacterial activity of PA.

Inactivation of Bacillus cereus spores in a tsuyu sauce using continuous ohmic heating with five sequential elbow-type electrodes

AIMS

The effect of ohmic heating (OH) in a pilot plant system which had a zig-zag shaped (elbow-type) ohmic heater with five sequential voltage electrodes was investigated on Bacillus cereus spores in a commercial tsuyu sauce.

METHODS AND RESULTS

The electrical field was fixed at 26·7 V cm(-1) with an alternating current frequency of 25 kHz. Raw tsuyu sauce (50 l) inoculated with B. cereus spores was submitted in a 4 × 3 factorial design to the OH system and heated at 95, 105, 115, and 125°C each for 30, 60, and 90 s. Survival of B. cereus spores and colour change in the commercial tsuyu sauce were both measured before and after treatment. As the treatment temperature and time increased, the number of surviving B. cereus spores decreased. The OH treatment in a bath-type process at 105°C for more than 30 s resulted in the total inactivation of the inoculated B. cereus spores (average 5·4 log reductions to undetectable levels after treatment). The OH protocol of heating at 105°C for 60 s which ensure complete eradication of the inoculated spores without compromising product quality was chosen and investigated for its suitability for commercial application on bulk quantities of samples (500 l). Reliable and reproducible reductions in B. cereus spore counts of 4·7-5·5 log CFU ml(-1) (mean ± standard deviation = 5·1 ± 0·3 CFU ml(-1) ) were achieved by the selected protocol of the continuous OH treatment (105°C for 60 s).

CONCLUSION

This study suggests that OH treatment with five sequential elbow-type electrodes has great potential as an industrial sterilizing method for liquid food contaminated with B. cereus spores.

SIGNIFICANCE AND IMPACT OF THE STUDY

This procedure will enhance the microbiological quality of liquid foods while minimizing quality deterioration.