• Korean Journal of Fisheries and Aquatic Sciences
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• v.50 no.4
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• pp.335-342
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• 2017

Oysters Crassostrea gigas are a globally popular shellfish for human consumption. As filter-feeding bivalve mollusks, oysters may harbor many microorganisms and chemicals that could pose potential human health risks. The objective of this study was to investigate the suitability of cultured oysters for raw consumption or use in seafood products by measuring concentrations of harmful microorganisms and chemicals in their flesh. Microbial concentrations in cultured oysters were found to be: $1.0{\times}10^2-6.0{\times}10^4CFU/g$ (viable cell counts), not detected $(ND)-5.4{\times}10^3CFU/g$ (coliform bacteria), $ND-1.3{\times}10^2CFU/g$ (E. coli), and $ND-4.6{\times}10^3CFU/g$ (Vibrio parahaemolyticus). Other pathogenic bacteria, including Enterohemorrhagic E. coli (EHEC), Listeria monocytogenes, Staphylococcus aureus, and Salmonella spp., were not detected in any samples. Heavy metal concentrations of cultured oysters were ND-0.239 mg/kg (total mercury), ND-1.091 mg/kg (lead), ND-0.968 mg/kg (cadmium). The concentrations of benzo(a)pyrene ranged from $0.280-0.880{\mu}g/kg$. Paralytic shellfish poison ranged from ND-0.58 mg/kg, while diarrhetic shellfish poison was not detected. No radioactivity was detected. These results suggest that oysters intended for raw consumption or use in seafood products should be subjected to chemical and biological controls.

• Mycobiology
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• v.48 no.5
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• pp.410-417
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• 2020

Fungal ecological interactions play a key role in structuring community assemblages. These associations may involve both antagonistic and synergistic relationships, which are commonly influenced by abiotic factors such as nutrient conditions. However, information for extreme, oligotrophic systems remain poor. Herein, interactions among key members of the aquatic transient fungal community (Aspergillus niger, Cladosporium sp., and Coprinellus micaceus) of a low-nutrient freshwater system in the Cuatro Ci enegas Basin, Mexico were studied. Pairwise interaction bioassays were explored in vitro under different nutrient conditions, including carbohydrates-rich, carbohydrates and amino peptides-rich, and low nutrients. Our results indicated that antagonistic patterns prevail among the studied taxa. However, nutrient-dependent changes were observed in Cladosporium sp. shifting to synergy under carbohydrates-rich conditions, suggesting changes in the fungal community composition as a result of nutrient enrichment. Remarkably, our findings contrast with previous work demonstrating mainly synergistic interactions between our tested fungal isolates and co-occurring autochthonous bacteria (Aeromonas spp. and Vibrio sp.) under low-nutrient conditions. This observation may indicate that bacteria and fungi exhibit distinct community-level responses, driven by nutrient conditions. This contributes to the knowledge of fungal community dynamics and interspecific interactions in an oligotrophic ecosystem, highlighting the relevance of nutrient-based shifts and antagonistic interactions in ecosystem dynamics.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.53 no.6
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• pp.861-869
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• 2020

This study was conducted to investigate the suitability of frozen oysters as a raw material for the preparation of seafood products by measuring the concentrations of harmful microorganisms and chemicals in thawed flesh. The microbial concentrations in thawed oysters were 2.3-5.0 log CFU/g for viable cell counts, not detected (ND)-1.0 log CFU/g for coliform bacteria, and ND for Escherichia coli and pathogenic bacteria such as Staphylococcus aureus, Salmonella spp., Listeria monocytogenes, Vibrio parahaemolyticus, Enterohemorrhagic Escherichia coli (EHEC), and Clostridium perfringens. In frozen oysters, the heavy metal concentration for viable cell counts was ND-0.030 mg/kg, for lead was ND-0.393 mg/kg, and for cadmium was 0.021-0.597 mg/kg. Benzo(a)pyrene, shellfish poison (paralytic shellfish and diarrhetic shellfish poisons), and radioactivity were not detected in the thawed oysters. These results suggest that frozen oysters can be safely used as a raw material for the preparation of seafood products.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.55 no.4
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• pp.431-436
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• 2022

For the safety assessment of microbiological and chemical hazards in katsuobushi, fifteen samples of katsuobushi were purchased from supermarkets. The contamination levels of total viable bacteria, coliforms, Escherichia coli, and nine pathogenic bacteria [Staphylococcus aureus, Salmonella spp., Listeria monocytogenes, Bacillus cereus, Vibrio parahaemolyticus, Clostridium perfringens, Enterohemorrhagic E. coli (EHEC), Yersinia enterocolitica and Campylobacter jejuni/coli] were quantitatively or qualitatively assessed. Additionally, the heavy metals (total and methyl mercury) content, radioactivity (¹³¹ I, ¹³⁴ Cs⁺ and ¹³⁷ Cs) were quantitatively assessed. Microbial and chemical analyses were performed using standard methods in Korean food code. The contamination level of total viable bacteria was 2.70 (1.18-4.42) log CFU/g. Coliforms, E. coli and S. aureus were not detected in any samples. Other eight pathogenic bacteria were negative in all samples. The contamination levels of total and methyl mercury were 0.366 (0.227-0.481) and 0.120 (0.002-0.241) mg/kg, respectively. In addition, radioactivity was not detected in any samples. The results will be helpful in revitalizing domestic use and boosting exports of katsuobushi because the microbiological and chemical safety of katsuobushi has been assured. Furthermore, the results may be used as a basis for performing chemical and microbial risk assessments of katsuobushi.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.57 no.3
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• pp.203-208
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• 2024

Fifteen cultured frozen abalone Haliotis discus hannai samples were purchased from supermarkets, traditional markets, online markets, and processing factories throughout Korea for the safety assessment of microbiological and chemical hazards. Sanitary-indicative (total viable bacteria, coliforms, and Escherichia coli) and pathogenic (Staphylococcus aureus, Salmonella spp., Listeria monocytogenes, Vibrio parahaemolyticus, Clostridium perfringens, and Enterohemorrhagic E. coli) bacterial contamination levels were assessed quantitatively or qualitatively. Additionally, heavy metal content (lead, cadmium, and total mercury) and radioactivity (¹³⁴CS+¹³⁷CS, ¹³¹I) were quantitatively assessed. The total viable bacterial count was 4.3×10² CFU/g, while coliform count was 50 CFU/g. E. coli was not detected in any of the samples (count < 10 CFU/g). All six pathogenic bacteria tested negative qualitatively. The average lead, cadmium, and total mercury contamination levels in the cultured frozen abalone were 0.100±0.057, 0.145±0.061, and 0.015±0.001 mg/kg, respectively. Moreover, none of the samples were radioactive. According to the results of this study, cultured frozen abalones distributed in all types of markets were safe from all microbiological and chemical hazards.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.31 no.6
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• pp.920-926
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• 1998

To investigate the effects of yellow loess on the microbial community after applying into C. polykrikoides as a red tide centrol method during decomposition process, we conducted this study using microcosm experiments, which consisted of sediment collected from Jinhae and Masan bay. The composition, number of bacteria and respiratory electron transport system activity (ETSA) were analyzed. The number of heterotrophic bacteria examined in the samples of both stations reached maximum value within 12 hrs with $10^7$ cells/dry g, independent with the yellow loess applied. In addition, a differenee in the variation of heterotrophic bacterial composition was not observed by adding the yellow loess, and Vibrio spp. always appeared during the culture periods, However, in day 8 culture, the sulfate reducing bacteria was $3.8\times10^7$ cells/dry g in Masan bay and $5.5\times10^6$ cells/dry g in Jinhae bay samples without yellow loess, and these were 120, 350 fold-and 160, 420 fold-increased when yellow loess was added (1 : 1, 1 : 2). The average ETSA was 6.8$\~$7.6 $\mu$g formazan $h^{-1}$ dry $g^{-1}$ independently with yellow loess in aerobic condition for both samples, but activity was decreased by addition of yellow loess in anaerobic. Thus the addition of yellow loess to marine sediment seems to have an effect to inhibit the anaerobic decomposition process and growth of sulfate reducing bacteria which lead to the bad condition of marine environments.

• Korean Journal of Food Science and Technology
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• v.38 no.1
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• pp.121-127
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• 2006

Microbial and nutritional characteristics of Kwangchun shrimp Jeotgal (salt-fermented shrimp) were assessed. Total mesophilic bacteria, coliforms, and S. aureus counts in Kwangchun shrimp Jeotgal were 3.48-5.42, 2.22-2.95, and 0.58-2.51 $log_{10}CFU/g$, respectively. Yeast and mold were detected only in Ohjeot (1.99 $log_{10}CFU/g$) and Yookjeot (1.47 $log_{10}CFU/g$). B. cereus, L. monocytogenes, Vibrio spp. and E. coli were not detected in Kwangchun shrimp Jeotgal, which contained abundant macrominerals (Ca, Mg, Na, K), with Na showing highest content. Palmitic acid content was higher than those of other saturated fatty acids. Eicosapentaenoic acid and docosahexaenoic acid contents were higher than those of other poly unsaturated fatty acids. Results showed Kwangchun shrimp Jeotgal is safe microbiologically with abundant nutritional components.

• Journal of Life Science
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• v.33 no.1
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• pp.56-63
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• 2023

In this study, two cases of food poisoning caused by Salmonella that occurred in Gyeongsangnam-do in September 2021 are reported. One of the outbreaks occurred in a school and the other in a company. The molecular epidemiological characteristics of the isolated strains in the two outbreaks were analyzed. In the case of the school outbreak, 29 (4.9%) of 588 individuals experienced diarrhea and abdominal pain. As a result of a test of 36 individuals (patients, n=29; cook workers, n=7), Salmonella enterica serotype Enteritidis was detected in 17 (47.2%) patients, suggesting this serotype was the principal cause. Meanwhile, Salmonella spp. were not detected in 35 food and environmental samples. In the company outbreak, 87 (3.0%) of 2,900 individuals who had intaked from the same source experienced diarrhea, abdominal pain, and fever. In a test of 50 individuals (patients, n=40; cook workers, n=10), S. Enteritidis was detected in 28 patients (56.0%). Also, Vibrio cholerae (NAG) was detected in four patients with S. Enteritidis, and V. cholerae (NAG) only was detected in one patient. Salmonella spp. were not detected in 118 preserved foods, but S. Enteritidis was detected in one eaten food (toast) delivered in group by the company. Through PFGE genetic homology analysis of the isolated strains, all S. Enteritidis detected in patients and consumed foods were the same type. It seems that these S. Enteritidis isolates were the same type as detected in a previous school outbreak and in patients of group food poisoning in other regions, leading to an enhanced problem of food poisoning and epidemiology. Our analytic results can provide data for epidemiological management and food poisoning prevention based on molecular characteristics.

• Journal of Life Science
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• v.19 no.2
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• pp.277-283
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• 2009

Biogenic amines are generally formed through the decarboxylation of specific free amino acids by exogenous decarboxylases released by microbial species associated with the fish products and fermented feeds. This study was conducted to investigate the properties of e tuna waste regarding the control of degradation of biogenic amines (histamine, tyramine, tryptamine, putrescine, and cadaverine) that might be related with the anti-nutritional factor of the tuna waste that is used for manufacturing domestic fish meal. The values of pH and the salt content were 6.51, 3.35% in tuna waste and 5.58 and 5.83% in tuna fish meal, respectively. The strains and dominant bacteria tested in the tuna waste sample were 9.20, 9.29, 5.67, 7.82 and 7.58 log CFU/g of total bacteria, aerobic plate count (APC), total coliform (TC), Lactobacillus spp. and Bacillus spp., respectively. The main histamine forming-bacteria (HFB) in tuna waste were detected by silica gel thin-layer chromatography (TLC) and 7 histamine-forming bacterial species were isolated among microbes grown in selective medium. The histamine concentration was determined by detection of fluorescence of ο-phthaldialdehyde (OPA) derivatives using HPLC and the date were used to reconfirm the identities of the amine-producing bacteria. The 15 histamine- forming bacteria strains grown in trypicase soy broth (TSB) supplemented with 1% L-histidine (TSBH) were identified as Lactococcus(L.) lactis subsp. lactis, Klebsiella pneummonlae, L. garvieae 36, Vibrio olivaceus, Hafnia alvei and L. garvieae which were main dominant amine - producing strains, and Morganella morganii identified by 16S ribosomal RNA (rRNA) sequencing with PCR amplification. A Phylogenetic tree generated from the 16S rRNA sequencing data showed different phyletic lines that could be readily classified as biogenic amine forming gram-positive and negative bacteria.

• Journal of the Korean Society of Food Science and Nutrition
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• v.37 no.3
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• pp.379-389
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• 2008

This study was conducted to assess the microbiological quality of raw and cooked foods served in the elementary school food service. Raw and cooked food samples were collected from 11 selected elementary schools in both June to July and September to October of 2005. Petrifilm plates were used to determine (in duplicate) total aerobic colony counts (PAC), Enterobacteriaceae (PE), coliform counts (PCC), and E. coli counts (PEC). Heavy contamination of Enterobacteriaceae (from 0.08 to 7.40 log CFU/g) and total coliform (0.50 to 6.52 log CFU/g) were observed in raw materials and cooked foods. Escherichia coli (E. coli) were detected in the sample of currant tomato (3.70 log CFU/g), sesame leaf (3.59 log CFU/g), dropwort (0.20 log CFU/g), crown daisy (3.15 log CFU/g), parsley (3.00 log CFU/g), peeled green onion (1.74 log CFU/g), frozen pork (0.65 log CFU/g), frozen beef (0.20 or 1.50 log CFU/g), chicken (1.78 log CFU/g), and young radish leaf seasoned with soybean paste (1.24 log CFU/g). Multiplex PCR system was used to determine the food-borne pathogens: Salmonella spp., Bacillus cereus (B. cereus), E. coli O157:H7, Staphylococcus aureus, Listeria monocytogenes (L. monocytogenes), Vibrio parahaemolyticus, Campylobacter jejuni (C. jejuni), Shigella spp., B. cereus was detected in 19 samples of raw materials and 8 samples of cooked foods. With regard to quantitative analysis, B. cereus counts exceeded 5.46, 3.48 and 1.79 log CFU/g in sesame leaf, peeled green onion and seasoned mungbean jelly, respectively. E. coli O157:H7 was detected on 2 samples of frozen beefs, and its biochemical characteristics of one beef sample was confirmed with API 20E kit (93.7%). L. monocytogenes was detected in fried rice paper dumpling, but the presumptive colonies were not detected onto the conventional plate. C. jejuni was detected in peeled & washed onion.