• Korean Journal of Fisheries and Aquatic Sciences
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• v.51 no.4
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• pp.450-455
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• 2018

We examined correlations of the density of fish farms with the distributions of indicator bacteria (Escherichia coli, fecal streptococci) and a bacterial fish pathogen (Streptococcus parauberis) off the coastline of Jeju Island. Seawater samples were collected at four coastal sites on the Island [Aewol (control), Gujwa, Pyoseon and Daejeong] in June, August and October 2016. The indicator bacteria were generally more frequently isolated from samples taken in August when water temperatures and human activities on nearby beaches were highest. Although fish farms were least common at Daejeong, the numbers of isolated fecal indicator bacteria were highest in the seawater and effluent water collected from this site. Hence, fish farms were not likely major contributors of indicator bacteria at Daejeong. We found discrepancies between the isolated bacterial counts and the predicted bacterial copy numbers deduced from our qPCR results, indicating that this pathogen may exist in a viable but non-culturable (VBNC) state in seawater. Thus, livestock wastewater and chemical fertilizer loading off Jeju Island may negatively impact seawater quality more than the effluent released from fish farms does.

• Journal of fish pathology
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• v.37 no.1
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• pp.133-138
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• 2024

This study is a report on combinational effects between four sesquiterpene lactones (SLs) from bay laurel (Laurus nobilis) leaves, and oxytetracycline (OTC) or amoxicillin (AMX) against four fish pathogenic bacteria such as Vibrio anguillarum, V. harveyi, Edwardsiella tarda, and Streptococcus iniae. Individually, four SLs exerted little antibacterial activity against fish pathogenic bacteria. However, when combined with OTC or AMX, they showed synergistic interaction against pathogenic bacteria. Especailly, zaluzanin C (1) reduced the MIC of OTC (or AMX) eight-fold. Our results showed that combinations of SLs with antibiotics (ABTs) are more effective than ABTs alone to control pathogenic bacteria. The highest synergistic effect was observed when zaluzanin C (1) was combined with OTC or AMX against V. harvey or S. iniae, displaying significant reductions of MICs up to 8-fold (0.125 to 0.015 ㎍/mL and 0.0078 to 0.0009 ㎍/mL). In addition, zaluzanin C (1) improved the antibiotic potency of OTC against OTC resistant V. harveyi (250 ㎍/mL to 62.5 ㎍/mL). Synergism between ABTs and phytochemical such as SLs could be a therapeutically helpful concept to improve the efficacy of ABTs and prevent antibiotic resistance. These results suggest that SLs can be used as an alternative to reduce antibiotic resistance in aquaculture.

• Korean Journal of Microbiology
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• v.9 no.2
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• pp.47-54
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• 1971

This study is concerned to the microbial population and its effects in the fish paste products. Experimental results were summarized as following orders ; 1) The number of bacteria in accordance with raw materials and coocking site waas known to as ; Wheat flor - $7.0{\times}10^8$/gram , Brayed fish meat - $2.0{\times}10^7$/gram, Cooking table - $6.1{\times}10^6$/$1.54cm^2$Chopped fish meat -$4.1{\times}10^6$/gram, Wooden plate - $5.5{\times}10^5$/218.32cm, Sodium chloride - $8.8{\times}10^4$/gram, Wheat starch - $4.5{\times}10^4$/gram, Fish meat - $2.3{\times}10^4$/gram. However, there were a few bacterial numbers less than 300 per gram of raw materials, such as monosodium glutamate, tap water, sugar, saccharine and eggs. 2) Bacterial population in the raw materials might be changed according to the conditions of preservation. 3) When the heat tratment is used for the preservation, the thermal effects were rarely found at the interior part of fish paste products. Conduction of heat into the interior part dose not rise about $84^{\circ}C$ and the survival of bacteria could be possible under the condition. Therefore, cooking being used requires further studies. 4) Number of bacteria in the fish paste products sold in the market was higher on April and May than those on June. Especially on June, the number of bacteriz in the interior part were found higher than those in the exterior part of the products.

• Journal of Microbiology and Biotechnology
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• v.10 no.3
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• pp.423-428
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• 2000

Bacteriocins are classified as proteins which are produced by heterogeneous groups of bacteria, having and antimicrobial effect of the closely related organisms. Recently, bacteriocins derived from lactic acid bacteria and other food-related organisms have been the subject of much research on potential food biopreservatives. The goal of this study was to screen and characterize the bacteriocinogenic lactic acid bacteria from Jeot-gal(commercial fermented fish foods). All bacteriocinogenic isolates were identified as lactic acid bacteria. Isolates NK24, NK34, and SA72 were tentatively identified as Lactobacillus brevis, according to the API 50 CHL kit database. All antimicrobial substances produced from four lactic acid bacteria isolates completely lost their antibacterial activity after being treated with some proteases, indicating to their proteinaceous nature. The bacteriocin produced from isolates NK24, NK34, and SA72 showed a broad spectrum of activity when compared to those produced from isolate SA131. All bacteriocins isolated during the course of this study showed a bactericidal mode of inhibition.

• Journal of fish pathology
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• v.12 no.1
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• pp.42-48
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• 1999

The disinfectant effects of total residual oxidants (TROs) produced by ozonization of natural sea water were investigated against fish pathogenic bacteria isolated from flounder and red seabream. The concentration of 0.1 mg TROs/liter was stable for 20 min in filtered natural seawater, and those of 0.3 and 0.5 mg TROs/liter were also stable for more 1 hr. Disinfectant effects of TRO against Edwardsiella tarda, Vibrio sp., Streptococcus sp. and Staphylococcus sp. were observed with a concentration of 0.1 mg/liter for 180 sec, and the treatment killed more than 99.9% of bacterial cells. With TROs of 0.3 to 0.5 mg/ liter, the viable cells of the bacteria were reduced by more than 99.99% in 60 sec.

• Journal of Environmental Health Sciences
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• v.36 no.6
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• pp.496-501
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• 2010

Fish pathogenic bacteria are a considerable danger of farmed fish and a source of economic loss in the fish farming industry. In this study, $Nanoxil^{(R)}$ was compared to hydrogen peroxide and a silver colloid in terms of disinfection efficacy against E. tarda, V. anguillarum and S. iniae. A bactericidal efficacy test conducted by a broth dilution method was used to determine the lowest effective dilution of the disinfectant following exposure to test bacteria for 30 min at $4^{\circ}C$. $Nanoxil^{(R)}$ and test bacteria were diluted with distilled water (DW), hard water (HW) or an organic matter suspension (OM) according to the treatment condition. Under the OM condition, the bactericidal activity of $Nanoxil^{(R)}$ against E. tarda exhibited a lowered efficacy compared to that under the DW and HW conditions. $Nanoxil^{(R)}$ at 500 fold (dilutions on) under all of the conditions demonstrated a high bactericidal efficacy against S. iniae. As $Nanoxil^{(R)}$ possess bactericidal efficacy against fish pathogenic bacteria such as E. tarda, V. anguillarum and S. iniae, this disinfectant solution can be used to limit the spread of fish bacterial diseases.

• Journal of fish pathology
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• v.18 no.2
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• pp.147-156
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• 2005

To obtain antimicrobial algae against fish pathogenic bacteria, we screened 80% methanolic extracts of 30 algae using fish pathogenic bacteria, Staphylococcus sp., Streptococcus sp., Edwardsiella tarda and Vibrio anguillarum. Among them, Corallina officinalis, Dumontia simplex, Gloipeltis furcata, Grateloupia lanceolata and Grateloupia turuturu were effective for growth inhibition of a Gram-positive bacterium, Staphylococcus sp.. Sargassum thunbergii and Polysiphonia morrowii exhibited significant inhibitory effects against the growth of Gram-negative bacteria, both E. tarda and V. anguillarum. Moreover, antimicrobial activity-guided fractionation for P. morrowii extract yielded significantly active 90% methanolic fraction. This fraction significantly inhibited the growth of E. tarda exhibiting a MIC of 1 mg/ml. In addition, its antimicrobial activity was stable under various pH conditions.

• Journal of Korean Society on Water Environment
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• v.24 no.2
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• pp.214-220
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• 2008

Nitrifying bacteria were detected by fluorescent in situ hybridization (FISH) method at 6 sampling sites with different eutrophication degree in the Nak-Dong River and their tributaries. And conventional physico-chemical parameters including $NH_4-N$, $NO_3-N$, and TN were determined concurrently. In rainy period (July), there was no noticeable difference between the number of ammonia/nitrite-oxidizing bacteria detected at each site except Sang-Ju and the ratio of nitrifying bacteria to total counts stained by DAPI varied in 6~33%. By contrast, in the dry period (October), both of bacterial population was increased differently and the ratio of nitrifying bacteria to total counts ranged more widely from 6% in heavily polluted water zone, Hwa-Won to 60% in upper tributary with high agricultural land use. Byung-Sung-Chun. In January, the numbers of ammonia-oxidizing bacteria was reduced up to one tenth, while those of nitrite-oxidizing bacteria was apparently increased maybe due to high DO and low DOC.

• Korean Journal of Veterinary Service
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• v.38 no.2
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• pp.65-70
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• 2015

The present study was to investigate in vitro antimicrobial effects of propolis against six different fish bacterial pathogens, Aeromonas hydrophila, Edwardsiella tarda, Vibrio vulnificus, V. parahaemolyticus, A. salmonicida subsp. masoucida, A. salmonicida subsp. salmonicida) using minimum inhibitory concentration (MIC) and minimum bacteriocidal concentration (MBC) tests. In the results, propolis exhibited antimicrobial activity against all bacteria used in the present study, but there was no marked difference in bacterial species except Vibrio species. Collectively, propolis was thought to be an usefulness antimicrobial substance for controlling bacterial diseases in the fish industry.

• Asian-Australasian Journal of Animal Sciences
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• v.13 no.7
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• pp.991-994
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• 2000

Single cell of an indigenous phototrophic bacterium, Rhodovulum sulfidophilum, was incorporated in commercial fish feed for Oreochromis niloticus. The bacterial cell was analyzed for nutritional value and tested for toxicity and acceptability as an aquaculture feed supplement. The results showed higher survival rate and significantly higher growth rate (p<0.001) in O. niloticus fed with the bacteria incorporated fish feed. It is suggested that R sulfidophilum can be utilized as an aquaculture feed supplement.