• 한국어병학회지
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• 제32권2호
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• pp.69-80
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• 2019

We performed MLSA (multilocus sequence analysis) and phenotypic characterization of Aliivibrio species isolated from walleye pollock (Gadus chalcogrammus) maintained in 3 different facilities of Gangwon Province, the east coast of Korea. Of 38 Aliivibrio species identified by 16S rDNA sequences, 12 strains were randomly selected and MLSA was conducted with 5 house-keeping genes (gapA, gyrB, pyrH, recA and rpoA) and 16S rDNA gene. Phylogenetic analysis and homology of the concatenated sequences (4,580 bp) with other Vibrionaceae genera revealed that 4 strains (GNGc16.1, YYGc16.1, YYGc16.2, GSGc18.1) were identified as Aliivibrio logei and one strain (GSGc16.1) as A. wodanis. One strain (GSGc17.1) was tentatively identified as A. logei, but needs further analysis because it did not belong to the same clade with A. logei type strain. 6 strains (GSGc17.2, GNGc16.2, GSGc16.2, GSGc17.3, GSGc18.2, GSGc17.4) need further investigation as potential novel species. Either phenotypic characterization or 16S rDNA sequence alone did not provide enough information for identification of Aliivibrio strains at the species level. A. logei and A. wodanis are generally known as non-pathogenic bacteria, but also known as opportunistic or secondary pathogens of cold water fishes. Cares should be taken to prevent potential outbreaks due to these bacteria, although there was no outbreaks during the sampling period.

• Clinical and Experimental Pediatrics
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• 제60권7호
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• pp.221-226
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• 2017

Purpose: Escherichia coli sequence type (ST) 131, a multidrug-resistant clone causing extraintestinal infections, has rapidly become prevalent worldwide. However, the epidemiological and clinical features of pediatric infections are poorly understood. We aimed to explore the characteristics of ST131 Escherichia coli isolated from Korean children with urinary tract infections. Methods: We examined 114 uropathogenic E. coli (UPEC) isolates from children hospitalized at Chung-Ang University Hospital between 2011 and 2014. Bacterial strains were classified into STs by partial sequencing of seven housekeeping genes (adk, fumC, gyrB, icd, mdh, purA, and recA). Clinical characteristics and antimicrobial susceptibility were compared between ST131 and non-ST131 UPEC isolates. Results: Sixteen UPEC isolates (14.0%) were extended-spectrum ${\beta}-lactamase$ (ESBL)-producers; 50.0% of ESBL-producers were ST131 isolates. Of all the isolates tested, 13.2% (15 of 114) were classified as ST131. There were no statistically significant associations between ST131 and age, sex, or clinical characteristics, including fever, white blood cell counts in urine and serum, C-reactive protein, radiologic abnormalities, and clinical outcome. However, ST131 isolates showed significantly lower rates of susceptibility to cefazolin (26.7%), cefotaxime (40.0%), cefepime (40.0%), and ciprofloxacin (53.3%) than non-ST131 isolates (65.7%, 91.9%, 92.9%, and 87.9%, respectively; P<0.001 for all). ESBL was more frequently produced in ST131 (53.3%) than in non-ST131 (8.1%) isolates (P<0.01). Conclusion: ST131 E. coli isolates were prevalent uropathogens in children at a single medical center in Korea between 2011 and 2014. Although ST131 isolates showed higher rates of antimicrobial resistance, clinical presentation and outcomes of patients were similar to those of patients infected with non-ST131 isolates.

• The Plant Pathology Journal
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• 제34권4호
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• pp.269-285
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• 2018

Bacterial leaf blight is a major disease of eucalypt, especially under nursery conditions. Different bacterial species have been associated with the disease in several countries, and despite its importance worldwide, it is not clear to date whether similar disease symptoms are caused by the same or by different etiological agents. In this study, 43 bacterial strains were isolated from blighted eucalypt leaves collected in different geographic areas of Brazil and inoculated onto a susceptible eucalypt clone. Polyphasic taxonomy, including morphological, physiological, biochemical, molecular, and pathogenicity tests showed that only certain strains of Xanthomonas axonopodis caused symptoms of the disease. Strains varied in their aggressiveness, but no correlation with geographic origin was observed. MLSA-based phylogenetic analysis using concatenated dnaK, fyuA, gyrB and rpoD gene sequences allocated the strains in a well-defined clade, corresponding to Rademarker's group RG 9.6. Inoculation of nineteen plant species belonging to seven botanical families with representative strain LPF 602 showed it to be pathogenic only on Eucalyptus spp, and Corymbia spp. Based on distinct biochemical and pathogenic characteristics that differentiate the eucalypt strains from other pathovars of the X. axonopodis species, here we propose their allocation into the new pathovar X. axonopodis pv. eucalyptorum pv. nov.

• 대한수의학회지
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• 제56권2호
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• pp.129-131
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• 2016

Five eastern great egrets with a history of ataxia, wry neck, and wet feathers were submitted to the Veterinary Diagnostic Center for pathologic examination. Slightly enlarged livers with diffuse white-grayish nodules were observed. Microscopically, the hepatic and lung parenchyma contained granulomatous lesions consisting of central necrosis. Some hearts showed myofiber necrosis with infiltration of histiocytes and heterophils. Partial 16SrRNA and gyrB gene sequences of all isolates showed high similarities (99-100%) to those of Salmonella (S.) enterica subsp. enterica. Based on pathological and molecular biological results, S. enterica subsp. enterica systemic infections were diagnosed in eastern great egrets of Korea.

• 한국어병학회지
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• 제35권2호
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• pp.215-223
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• 2022

Disease including parasite, bacteria and virus cause serious mortality to salmonid fish in the aquaculture. In this study, we investigated the current disease status of the rainbow trout (Oncorhynchus mykiss) and coho salmon (Oncorhynchus kisutch) in Yanayang, Pyeongchang, Jeongseon and Yeongwol of Gangwon province in 2021 and performed molecular characterization of those pathogen. For parasites, Ichthyophthirius multifiliis was observed at 2 farms. For bacteria, we identified Aeromonas sobria from kidney of rainbow trout using phylogenetic analysis of gyrB gene. A. salmonicida were isolated from necrosis site of gill cover and fin in coho salmon and necrotic lesion of fin in rainbow trout. Phylogenetic analysis using vap gene indicated that A. salmonicida isolated in this study were clustered with previously reported A. salmonicida subsp. salmonicida isolates. For virus, JRt-Nagano type of infectious haematopoietic necrosis virus was detected in rainbow trout, but infectious pancreatic necrosis virus and Oncorhynchus masou virus were not detected. These results provide useful information for the prevention of disease spread and transmission when cultivating new species such as Atlantic salmon in Korea.

• The Plant Pathology Journal
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• 제39권4호
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• pp.409-416
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• 2023

Bacterial leaf blight of carrots caused by Xanthomonas hortorum pv. carotae (Xhc) is an important worldwide seed-borne disease. In 2012 and 2013, symptoms similar to bacterial leaf blight were found in carrot farms in Jeju Island, Korea. The phenotypic characteristics of the Korean isolation strains were similar to the type strain of Xhc. Pathogenicity showed symptoms on the 14th day after inoculation on carrot plants. Identification by genetic method was multi-position sequencing of the isolated strain JJ2001 was performed using four genes (danK, gyrB, fyuA, and rpoD). The isolated strain was confirmed to be most similar to Xhc M081. Furthermore, in order to analyze the genetic characteristics of the isolated strain, whole genome analysis was performed through the next-generation sequencing method. The draft genome size of JJ2001 is 5,443,372 bp, which contains 63.57% of G + C and has 4,547 open reading frames. Specifically, the classification of pathovar can be confirmed to be similar to that of the host lineage. Plant pathogenic factors and determinants of the majority of the secretion system are conserved in strain JJ2001. This genetic information enables detailed comparative analysis in the pathovar stage of pathogenic bacteria. Furthermore, these findings provide basic data for the distribution and diagnosis of Xanthomonas hortorum pv. carotae, a major plant pathogen that infects carrots in Korea.

• Journal of Microbiology and Biotechnology
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• 제27권3호
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• pp.460-470
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• 2017

Mussels are major fouling organisms causing serious technical and economic problems. In this study, antifouling activity towards mussel was found in three compounds isolated from a marine bacterium associated with the sea anemone Haliplanella sp. This bacterial strain, called PE2, was identified as Vibrio alginolyticus using morphology, biochemical tests, and phylogenetic analysis based on sequences of 16S rRNA and four housekeeping genes (rpoD, gyrB, rctB, and toxR). Three small-molecule compounds (indole, 3-formylindole, and cyclo (Pro-Leu)) were purified from the ethyl acetate extract of V. alginolyticus PE2 using column chromatography techniques. They all significantly inhibited byssal thread production of the green mussel Perna viridis, with $EC_{50}$ values of $24.45{\mu}g/ml$ for indole, $50.07{\mu}g/ml$ for 3-formylindole, and $49.24{\mu}g/ml$ for cyclo (Pro-Leu). Previous research on the antifouling activity of metabolites from marine bacteria towards mussels is scarce. Indole, 3-formylindole and cyclo (Pro-Leu) also exhibited antifouling activity against settlement of the barnacle Balanus albicostatus ($EC_{50}$ values of 8.84, 0.43, and $11.35{\mu}g/ml$, respectively) and the marine bacterium Pseudomonas sp. ($EC_{50}$ values of 42.68, 69.68, and $39.05{\mu}g/ml$, respectively). These results suggested that the three compounds are potentially useful for environmentally friendly mussel control and/or the development of new antifouling additives that are effective against several biofoulers.

• 한국어병학회지
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• 제36권2호
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• pp.277-286
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• 2023

Korean rockfish, Sebastes schlegelii, is a representative bony fish that belongs to the family Scorpaenidae and the order Scorpaeniformes. It has high ecological and economic value and is widely cultivated in many East Asian countries, including South Korea, Japan and China. One of streptococci, Streptococcus iniae, is Gram-positive cocci with a negative reaction for catalase and oxidase. The Korean rockfish shows clinical signs when infected with S. iniae, such as body darkening, bleeding, enlarged kidneys, blurred eyes, abdominal distension, etc., ultimately leading to death. The Korean rockfish causes significant economic losses every year in South Korea due to streptococcosis. In this study, we identified bacteria from the fish using polymerase chain reaction and conducted analyses of hemolytic activity and biochemical tests using API 20 STREP and API ZYM systems. Results of confirming the hemolytic activity (n=4) observed in alpha-type hemolysis (25%), beta-type hemol- ysis (50%), and gamma-type hemolysis (25%) of isolates. The biochemical test results exhibited sig- nificant variation among S. iniae. Additionally, we performed intraperitoneal injection with S. iniae in the fish and analyzed the phylogenetic tree using housekeeping genes of S. iniae, including cpsD, arcC, glnA, groEL, gyrB, mutS, pheT, prkC, rpoB, and tkt, via multilocus sequence typing (MLST). The lethal dose (LD₅₀) showed strong pathogenicity, such as 3.34 × 10 colony-forming unit (CFU)/ml for 23FBStr0601 strain and 7.16 × 10 CFU/ml for 23FBStr0602 strain. 23FBStr0603 strain showed relatively low pathogenicity at 1.73 × 10⁵ CFU/ml. The strains 23FBStr0601 and 23FBStr0602, which showed strong pathogenicity, clustered into one monophyletic group. The 23FBStr0603 strain showed weak pathogenicity and formed a monophyletic group with KCTC 3657.

• The Plant Pathology Journal
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• 제33권5호
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• pp.488-498
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• 2017

The aim of this study was to identify volatile and agardiffusible antifungal metabolites produced by Bacillus sp. G341 with strong antifungal activity against various phytopathogenic fungi. Strain G341 isolated from four-year-old roots of Korean ginseng with rot symptoms was identified as Bacillus velezensis based on 16S rDNA and gyrA sequences. Strain G341 inhibited mycelial growth of all phytopathogenic fungi tested. In vivo experiment results revealed that n-butanol extract of fermentation broth effectively controlled the development of rice sheath blight, tomato gray mold, tomato late blight, wheat leaf rust, barley powdery mildew, and red pepper anthracnose. Two antifungal compounds were isolated from strain G341 and identified as bacillomycin L and fengycin A by MS/MS analysis. Moreover, volatile compounds emitted from strain G341 were found to be able to inhibit mycelial growth of various phytopathogenic fungi. Based on volatile compound profiles of strain G341 obtained through headspace collection and analysis on GC-MS, dimethylsulfoxide, 1-butanol, and 3-hydroxy-2-butanone (acetoin) were identified. Taken together, these results suggest that B. valezensis G341 can be used as a biocontrol agent for various plant diseases caused by phytopathogenic fungi.

• 생명과학회지
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• 제23권6호
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• pp.757-769
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• 2013

섬유소 분해효소(carbxymethylcellulase)를 생산하는 미생물을 해수에서 분리하여 16S rDNA 및 gyrase 유전자의 염기서열을 분석하여 동정한 결과, Bcaillus velezensis로 확인되었으며 B. velezensis A-68로 명명하였다. 이 균주가 생산하는 섬유소 분해효소의 생산 조건을 최적화하기 위하여 통계학적 방법인 response surface method (RSM)를 사용하였다. 이 균주의 생육에 최적인 왕겨, 효모 추출물 및 배지의 초기 pH는 60.2 g/l, 7.38 g/l 및 7.18이었으나, 섬유소 분해효소 생산에 최적인 왕겨, 효모 추출물 및 배지의 초기 pH는 50.0 g/l, 5.99 g/l 및 7.30이었다. 통계학적인 분석 결과, 균주의 생육 및 균주의 섬유소 분해효소 생산에 가장 큰 영향을 미치는 것은 효모 추출물이었다. 이 균주의 생육과 섬유소 분해 효소의 생산에 최적인 $K_2HPO_4$, NaCl, $MgSO_4{\cdot}7H_2O$ 및 $(NH_4)_2SO_4$의 농도는 각각 7.50, 1.00, 0.10, and 0.80 g/l이었다. 이 균주의 생육 및 섬유소 분해효소 생산에 최적인 온도는 각각 $30^{\circ}C$ 및 $35^{\circ}C$로 생육에 최적인 조건과 섬유소 분해효소 생산에 최적인 조건이 다름을 알 수 있었다. 이 균주가 생산하는 섬유소 분해효소의 생산성은 83.8 m/l이며, 이는 최적화하기 전의 생산성에 비하여 3.3배 증가한 것이다. 이 연구를 통하여 농업 부산물인 왕겨를 섬유소 분해효소 생산을 위한 기질로 개발하였으며, 해수에서 분리한 미생물을 사용함으로써 섬유소 분해효소의 생산기간을 3일로 단축할 수 있었다.