• Journal of fish pathology
• /
• v.26 no.2
• /
• pp.111-116
• /
• 2013

In this study, the disinfectant efficacy of Aqua farmsafe$^{(R)}$, composed of didecyldimethylammonium chloride (DDAC) and yucca extract was evaluated against Salmonella typhimurium and fish pathogens. Determination of the anti-microbial or anti-viral efficacy of the disinfectant was based on Animal, Plant and Fisheries Quarantine and Inspection Agency Regulation No. 2011-26, Korea. Anti-bacterial efficacy test by broth dilution method was used to determine the lowest effective dilution of the disinfectant following exposure to test bacteria for 30 min at $4^{\circ}C$. Aqua farmsafe and test bacteria or virus were diluted with distilled water (DW), standard hard water (SW) or organic matter dilution (OM) according to treatment condition. Under the our results, disinfectant efficacy of Aqua farmsafe$^{(R)}$ possesses 30~40 fold against fish pathogens including bacteria and virus compared to that on animal pathogenic bacteria, S. typhimurim. As the efficacy of Aqua farmsafe$^{(R)}$ against fish pathogen was investigated in vitro, a controlled field trial is required to determine whether the use of Aqua farmsafe$^{(R)}$ will be able to reduce fish diseases.

• Journal of fish pathology
• /
• v.21 no.3
• /
• pp.259-270
• /
• 2008

Disease surveillance was performed to monitor the prevalence of fish pathogens in wild marine fish caught in coastal offshore water in Korea. A total of 333 of fish samples were collected at set net or fish market at landing port in Pohang (East Sea), Taean (Western Sea), Goseong and Tongyeong (Southern Sea) and 21 species of pathogens causing clinical infections to farmed fish were investigated. The detection rates of fish pathogens from Mugili formes, Tetraodontiformes, Pleuroneciformes, Sorpaeniformes, erciformes and Clupeiformes were 90.9, 61.1, 47.6, 43.6, 37.2 and 11.8%, respectively. Comparing with prevalence of diseases seasonally, both the detection rates of bacteria and parasite were higher than those of virus in April but the detection rates of parasites were distinctively higher than those of bacteria in August with high water temperature. Virus were detected in fish samples caught in the Western and Southern Sea in April. The detected parasites were Trichodina, Ichthyophthirius, Dactylogyrus, Microcotyle, Bivagina, Caligus, Alella and Myxobolus. Among the bacterial pathogens, Vibrio, Streptococcus, Photobacterium, Psuedomonas were predominant. Viral nervous necrosis virus (VNNV) and flounder lymphocystis disease virus (FLDV) were detected from the 6 species of fish virus examined in this study.

• Journal of fish pathology
• /
• v.33 no.1
• /
• pp.63-69
• /
• 2020

Fish culture is constantly threatened by various infectious diseases which are largely transmitted by water. Plasma technology is being used to sterilize polluted water in many industries. In this study, two bacterial pathogens Aeromonas salmonicida and Streptococcus iniae, and a virus (viral hemorrhagic septicemia virus, VHSV) were subjected to plasma water that was produced by a corona discharge system. Growth of A. salmonicida was greatly inhibited from 10^5.61 CFU/ml in positive control to 10^3.51 CFU/ml in treated group by only 60 sec contact with plasma water. Similarly, S. iniae was inhibited from 10^5.85 CFU/ml to 10^3.40 CFU/ml. VHSV titer also decreased from 10^4.1 TCID₅₀/ml to 10^1.45 TCID₅₀/ml by the same treatment. Activation of water by the plasma was confirmed by the existence of ozone in the plasma water. These results suggest that plasma water could efficiently disinfect fish pathogens, possibly by the action of reactive oxygen species contained in the plasma water.

• Fisheries and Aquatic Sciences
• /
• v.16 no.4
• /
• pp.273-277
• /
• 2013

Vibriosis caused by Vibrio anguillarum and edwardsiellosis caused by Edwardsiella tarda are septicemic diseases of many commercially important freshwater and marine fishes, and threaten the aquaculture industry in Korea. Early diagnosis and accurate identification of these two bacterial species could help to prevent these diseases and minimize the damage to cultured marine species. This study designed a duplex polymerase chain reaction (PCR) method for the simultaneous detection of two major fish pathogens: V. anguillarum and E. tarda. Each pair of oligonucleotide primers exclusively amplified the target groEL gene of the specific microorganism. Twenty-two Vibrio and ten non-Vibrio enteric species were used to check the specificity of the primers, which were found to be highly specific for the target species, even among closely related species. The detection limit was 400 pg for V. anguillarum and 4 ng for E. tarda when mixed purified DNA was used as the template. This assay showed high specificity and sensitivity in the simultaneous detection of V. anguillarum and E. tarda from artificially inoculated seawater and fish.

• Fisheries and Aquatic Sciences
• /
• v.21 no.2
• /
• pp.6.1-6.10
• /
• 2018

The intention of this study was to identify the bacterial pathogens infecting Oreochromis niloticus (Nile tilapia) and Clarias gariepinus (African catfish), and to establish the antibiotic susceptibility of fish bacteria in Uganda. A total of 288 fish samples from 40 fish farms (ponds, cages, and tanks) and 8 wild water sites were aseptically collected and bacteria isolated from the head kidney, liver, brain and spleen. The isolates were identified by their morphological characteristics, conventional biochemical tests and Analytical Profile Index test kits. Antibiotic susceptibility of selected bacteria was determined by the Kirby-Bauer disc diffusion method. The following well-known fish pathogens were identified at a farm prevalence of; Aeromonas hydrophila (43.8%), Aeromonas sobria (20.8%), Edwardsiella tarda (8.3%), Flavobacterium spp. (4.2%) and Streptococcus spp. (6.3%). Other bacteria with varying significance as fish pathogens were also identified including Plesiomonas shigelloides (25.0%), Chryseobacterium indoligenes (12.5%), Pseudomonas fluorescens (10.4%), Pseudomonas aeruginosa (4.2%), Pseudomonas stutzeri (2.1%), Vibrio cholerae (10.4%), Proteus spp. (6.3%), Citrobacter spp. (4.2%), Klebsiella spp. (4.2%) Serratia marcescens (4.2%), Burkholderia cepacia (2.1%), Comamonas testosteroni (8.3%) and Ralstonia picketti (2.1%). Aeromonas spp., Edwardsiella tarda and Streptococcus spp. were commonly isolated from diseased fish. Aeromonas spp. (n = 82) and Plesiomonas shigelloides (n = 73) were evaluated for antibiotic susceptibility. All isolates tested were susceptible to at-least ten (10) of the fourteen antibiotics evaluated. High levels of resistance were however expressed by all isolates to penicillin, oxacillin and ampicillin. This observed resistance is most probably intrinsic to those bacteria, suggesting minimal levels of acquired antibiotic resistance in fish bacteria from the study area. To our knowledge, this is the first study to establish the occurrence of several bacteria species infecting fish; and to determine antibiotic susceptibility of fish bacteria in Uganda. The current study provides baseline information for future reference and fish disease management in the country.

• Korean Journal of Ichthyology
• /
• v.29 no.1
• /
• pp.62-68
• /
• 2017

The Alaska pollock (Gadus chalcogrammus) belongs to the family Gadidae; it is a cold water fish, and has been developed as a novel aquaculture species in Korea. In this study, we describe ongoing surveillance for aquatic animal pathogens based on growth stages. We investigated bacterial flora in rearing water, and monitored pathogens; we also analyzed histopathological traits of abnormal fish. In rearing water, the total bacterial counts were $2.1{\times}10^3cfu/mL$ and Vibrio spp. (52%) were predominant in the larvae stage. In the juvenile and adult stages, the total bacterial counts were $3.4{\times}10^3$ and $3.2{\times}10^2cfu/mL$, respectively (with Pseudomonas sp. as the predominant species; 90% and 52%). This result revealed that the bacterial flora in rearing water changed depending on the feeding types. No virulent-bacteria or problematic viruses (VHSV, viral hemorrhagic septicemia virus; NNV, nervous necrosis virus; MBV, marine birnavirus) were detected from outwardly healthy fish using either culture or PCR assay. Some juveniles (less than 5%) had gas bubbles on the gill lamellae, degeneration of the corneal epithelium, and choroid gland degeneration, suggesting that these symptoms were caused by external injury and secondary infection by opportunistic bacteria. Disease management is important to cope with disease emergence in the novel aquaculture species Alaska pollock.

• Food Science and Preservation
• /
• v.22 no.6
• /
• pp.886-892
• /
• 2015

The antimicrobial effects of ten isothiocyanates (ITCs) present in cruciferous vegetables and radish root hydrolysate were investigated against pathogenic bacteria from olive flounder. Minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) were measured against two gram-positive bacterial strains (Streptococcus parauberis, S. iniae) and four gram-negative bacterial strains (Edwardsiella tarda, Vibrio ichthyoenteri, V. harveyi, Photobacterium damselae) by using a broth microdilution technique. The antibacterial activity of ITCs was in the order sulforaphane > sulforaphene > phenylethyl ITC > erucin > benzyl ITC > iberin > I3C > allyl ITC > phenyl ITC > hexyl ITC. The susceptibility of fish pathogens to ITCs was in the order of V. harveyi > E. tarda > P. damselae > S. parauberis > S. iniae > V. ichthyoenteri. Antimicrobial activity (MIC) of radish root hydrolysate was 0.250 mg/mL against S. iniae, 0.438 mg/mL against S. parauberis, and 0.500 mg/mL against both E. tarda and V. harveyi. The aliphatic ITCs were potent inhibitors of the growth of fish pathogens, followed by aromatic ITCs and indolyl ITC. The presence of a double bond in the chemical structure of ITCs decreased antibacterial activity, while ITCs with a thiol (-S-) group and a longer carbon chain increased antibacterial activity. These results suggest that ITCs have strong antibacterial activities and may be useful in the prevention of fish pathogens.

• Korean Journal of Fisheries and Aquatic Sciences
• /
• v.47 no.1
• /
• pp.45-51
• /
• 2014

Scuticociliates are regarded as serious pathogens in marine aquaculture worldwide. In Korea, they cause mass-mortalities in fish such as the commercially important olive flounder Paralichthys olivaceus. In particular, mixed infections of scuticociliates with pathogenic bacteria have been commonly reported. During efforts to identify natural marine-algae derived products that possess anti-bacterial and anti-scuticociliate properties, we found that an 80% methanolic extract of the red alga Polysiphonia morrowii Harvey exhibits both anti-scuticociliate activity against Miamiensis avidus, which is a major causative agent of scuticociliatosis, and anti-bacterial activities against fish pathogenic bacteria. Activity-guided fractionation and isolation of the 80% methanolic extract of P. morrowii yielded three bromophenols, which were identified as 3-bromo-4,5-dihydroxybenzyl methyl ether (1), 3-bromo-4,5-dihydroxybenzaldehyde (2) and urceolatol (3) based on spectroscopic analyses. 3-bromo-4,5-dihydroxybenzyl methyl ether (1) showed the highest anti-bacterial and anti-scuticociliate activities, with a minimal inhibitory concentration (MIC) of $62.5{\mu}g/mL$ (against Vibrio anguillarum) and minimal lethal concentration (MLC) of 62.5 ppm (in seawater). Investigations of the anti-bacterial and anti-scuticociliate activities of seventeen bromophenol derivatives, including the three isolated natural bromophenols, showed that the existence of an electron donating group or atom with a non-covalent electron pair at $C_4$ of the 2-bromophenol structure may be important in anti-scuticociliate activity. These findings suggest that the extract and bromophenol derivatives of P. morrowii may provide useful alternatives in aquaculture anti-scuticociliate therapies.

• Journal of fish pathology
• /
• v.25 no.3
• /
• pp.263-270
• /
• 2012

This study surveyed for the prevalence of parasites, bacteria and viruses in four fish species, olive flounder (Paralichthys olivaceus), red sea bream (Pagrus major), black sea bream (Acathopagrus schlegeli) and black rockfish (Sebastes schlegeli) in 2010. The survey was aimed to compare the pathogens detected from wild and cultured fish for an epidemiological study. Anisakis sp. was predominantly detected from wild olive flounder and red sea bream (58.6% and 41.7% respectively), but not from the cultured fishes, suggesting anisakid infection is rare in cultured fish. The wild fish get in contact with the anisakids through their prey such as small fishes or crustaceans which carry the anisakids; whereas the cultured fish are fed with formulated feed, free of anisakids. Bacterial detection rates from the wild fishes examined in the study were lower than those of cultured fishes. Vibrio sp. dominated among detected bacterial population in cultured olive flounder (18%). Since vibriosis is known as a secondary infection caused by other stressful factors such as parasitic infections, handling and chemical treatment, it seems that cultured olive flounder are exposed to stressful environment. Viruses diagnosed in the study showed difference in distribution between wild and cultured fishes; hirame rhabdovirus (HRV) (0.1%) and lymphocystis disease virus (LCDV) (3.9%) were detected in the cultured olive flounder, but not in the wild fish, and marine birnavirus (MBV) (1.7%) and red sea bream iridovirus (RSIV) (3.2%) were detected from the wild and cultured red sea bream, respectively. From the survey conducted, it can be concluded that even though some pathogens (Trichodina sp., Microcotyle sp., etc.) are detected from both the wild and cultured fish, pathogens such as Anisakis sp., Vibrio sp. and LCDV showed difference in distribution in the wild and cultured host of same fish species and this can be attributed to their environmental condition and feeding.

• Journal of Veterinary Clinics
• /
• v.19 no.1
• /
• pp.19-22
• /
• 2002

The examination with 96 bacteria isolates for antibiotics susceptibility was resulted in exploring many antibiotics resistance isolates from the diseased fishes. Vibrio sp. isolates were demonstrated over 90% resistances for Penicillin (P), Amoxicillin (Amc), Erythromycin (I), Colistin (CL). Streptomycin (S). Novobiocin (NV) and Neomycin(N), these isolates were, however, appeared over 80% susceptibilities for Norfloxacin (Nor), CE and UB. In Edwardsiella tarda case, 90 to 100% high resistance was observed for P, Doxycycline (Do), Tetracyclin (Te), Oxytetracycline (T), E, CL, Sulfamethoxasoletrimetoprim (SXT), S, Oxolinic acid (OA), W, Neomycin(N), on the contrary, 90 to 100% high susceptibilities was found for Amc, Nor, Ciprofloxacin (Cip), Orbifloxacin (ORB), Enrofloxacin (ENR), Flumeguine (UB) and NA. CL, Pefloxacin (PEF),S, Flumeguine (UB), OA, NA, NV N was exhibited 90 to 100% resistances for Streptococcus sp., on the other hand, 100% susceptible to AMC and 80% susceptible to Do, Te, ENR and UB was recognised. Lastly, Photobacterium damsela subsp. piscicida was showed 100fe susceptible to Amc and 86% susceptible to NOR, CIP ENR and UB. As a consequence, fish bacterial pathogens isolated from Kyeongnam area, especially Tongyeong-si, Geoje-si, and Goseong-gun, were showed highly resistant to a variety of antibiotics available in the field.