• Journal of Oral Medicine and Pain
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• v.35 no.1
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• pp.19-29
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• 2010

Phytoncide, essential oil of trees, has microbicidal, insecticidal, acaricidal, and deodorizing effect. The present study was performed to examine the effect of phytoncide on Candida albicans, which is a commensal colonizer of the mucous membranes but has become an opportunistic pathogen. C. albicans was incubated with or without phytoncide extracted from Hinoki (Chamaecyparis obtusa Sieb. et Zucc.; Japanese cypress) and then changes were observed in its optical density, cell viability and morphology. As concentrations of phytoncide added to the culture medium increased, optical density and cell viability of C. albicans decreased. Minimum inhibitory concentration of phytoncide for C. albicans was observed to be 0.25%, and minimum fungicidal concentration was 0.5%. Numbers of morphologically atypical cells with electron-dense cytoplasm and granules and increased with increasing concentration of the phytoncide. At higher concentrations of phytoncide, compartments and organelles in the cytoplasm became indistinguishable. The overall results indicate that the phytoncide used for this study has a strong antimicrobial activity against C. albicans. Therefore, the phytoncide may be used as a candidate for prevention and therapeutic agent against oral candidiasis.

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

• Korean Journal of Food Science and Technology
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• v.52 no.1
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• pp.89-93
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• 2020

Vibrio vulnificus, an opportunistic pathogen, causes septicaemia when raw shellfish and fish are eaten by patients with hepatic diseases or reduced immunity. In this study, we evaluated inhibitory effects of some natural products on V. vulnificus growth using 96-well microplate assay. We found that Phyllanthus emblica L., Rosa chinensis Jacq., Rosa rugose Thub., and Chukrasia tabularis A. Juss. significantly inhibited V. vulnificus growth in Luria-Bertani (LB) broth. Among these four extracts, the inhibition diameter of Chukrasia tabularis was 16.00 ± 0.58 mm in disc diffusion assay on V. vulnificus growth. In addition, these four natural products protected HeLa cells from V. vulnificus-induced cytotoxicity. A cocktail containing these four products showed an inhibitory effect on V. vulnificus growth in seawater and shellfish by reducing its growth by 75.7% and 97%, respectively. These results suggest that these four natural products are safe and effective natural antimicrobial candidates to prevent V. vulnificus infection.

• Journal of Life Science
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• v.25 no.12
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• pp.1399-1407
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• 2015

Klebsiella pneumoniae is found in the normal flora of the skin, mouth, respiratory tract, urinary tract, and intestines in human. However, the stain is opportunistic pathogen, which is the causative agent of community acquired pneumonia. Corn silk has been known to be effective for antimicrobial activity against pathogenic bacteria, including K. pneumoniae, Staphylococcus aureus, Bacillus subtilis, Shigella spp., Salmonella spp., Escherichia coli, Pseudomonas aeruginosa, et al. In this study we focused on the antimicrobial properties of con silk water extract of K. penumoniae. K. pneumoniae isolates K. pneumoniae ATCC 13883 and broad-spectrum β-lactamase (BSBL), exteded-spectrum β-lactamase (ESBL), carbapenemase-producers. Antimicrobial susceptibilities were determined by the disk diffusion method. Searches for bla genes were performed by PCR amplication and direct sequencing. MacConkey agar plate medium was prepared using the corn silk extracts (50% or 100%) instead of distilled water for antimicrobial activity test. The microbial growth inhibitory potential of K. pneumoniae was determined by using the MacConkey agar plate spreading method, and the plate was incubated 18 hr at 37℃. Genes encoding β-lactamases including SHV-1 (n=8), SHV-2a (n=8), SHV-5 (n=2), SHV-11 (n=2), SHV-12 (n=18), TEM-1 (n=10), CTX-M-3 (n=2), CTX-M-14 (n=2), CTX-M-15 (n=1), GES-5 (n=5), KPC-2 (n=6), KPC-3 (n=4), and NDM-1 (n=2) were detected. The corn silk extract showed significantly antimicrobial activity against K. pneumoniae ATCC 13883, but BSBLs, ESBLs, and carbapenemase producers were not. Therefore, corn silk extract is thought to be able to assist in the prevention and rapid recovery of infectious disease caused by K. pneumoniae.

• Journal of Veterinary Clinics
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• v.27 no.1
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• pp.1-5
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• 2010

Enterocytozoon bieneusi, a microsporidian species, has emerged as an opportunistic pathogen in AIDS patients. This organism has also been identified in a wide range of animals, and the zoonotic potential of human infections is of particular interest. This study revealed that this organism was found with relatively high prevalence in feces of asymptomatic cattle in Korea. Fecal specimens were obtained from a total of 1,720 cattle in a slaughterhouse located in Chungnam province, Daejeon city and Chonbuk province. After removal of fecal debris by sieving and density gradient centrifugation, samples were examined by microscopic examination and then nested polymerase chain reaction (PCR). Microscopic examination with the modified trichrome staining for the fecal specimens revealed 194 (11.28%) positive calves for microsporidia spore. PCR using the specific primer for E. bieneusi revealed 79 (4.59%) positive calves. The infection ratio of microsporidia was higher in March than other season.

• Korean Journal of Microbiology
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• v.44 no.2
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• pp.85-92
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• 2008

Pseudomonas aeruginosa is an opportunistic human pathogen, causing a wide variety of infections including cystic fibrosis, microbial keratitis, and burn wound infections. The cell-to-cell signaling mechanism known as quorum sensing (QS) plays a key role in these infections and the QS systems of P. aeruginosa have been most intensively studied. While many literatures that introduce the QS systems of P. aeruginosa have mostly focused on two major acyl-homo serine lactone (acyl-HSL) QS signals, N-3-oxododecanoyl homoserine lactone (3OC12) and N-butanoyl homoserine lactone (C4), several new signal molecules have been discovered and suggested for their significant roles in signaling and virulence of P. aeruginosa. One of them is PQS (Pseudomonas quinolone signal; 2-heptyl-3-hydroxy-4-quinolone), which is now considered as a well-characterized major signal meolecule of P. aeruginosa. In addition, recent researches have also suggested some more putative signal molecules of P. aeruginosa, which are diketopiperazines (DKPs) and pyocyanin. DKPs are cyclic dipeptides and structurally diverse depending on what amino acids are involved in composition. Some DKPs from the culture supernatant of P. aeruginosa are suggested as new diffusible signal molecules, based on their ability to activate Vibrio fischeri LuxR biosensors that are previously considered specific for acyl-HSLs. Pyocyanin (1-hydroxy-5-methyl-phenazine), one of phenazine derivatives produced by P. aeruginosa is a characteristic blue-green pigment and redox-active compound. This has been recently suggested as a terminal signaling factor to upregulate some QS-controlled genes during stationary phase under the mediation of a transcription factor, SoxR. Here, details about these newly emerging signaling molecules of P. aeruginosa are discussed.

• Tuberculosis and Respiratory Diseases
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• v.72 no.1
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• pp.55-58
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• 2012

Mycobacterium szulgai is a rare nontuberculous mycobacterium found in Korea. It is an opportunistic pathogen and is usually isolated from patients with a history of alcoholism, chronic pulmonary disease, or an immunocompromising condition. We present here a case of M. szulgai isolated from a patient with a history of pulmonary tuberculosis. A 54-year-old man was admitted with dyspnea and febrile sensation. He had a history of pulmonary tuberculosis which occurred 30 years earlier and treatment with anti-tuberculosis medication. His chest computed tomography scan showed cavitary consolidation in both upper lungs. A sputum acid-fast bacilli (AFB) smear was positive and anti-tuberculous medication was started. However, a polymerase chain reaction for mycobacterium tuberculosis was negative and anti-tuberculous medication was stopped. M. szulgai was isolated on 3 separate sputum and bronchial wash fluid AFB cultures. He was treated with clarithromycin, rifampicin, and ethambutol. After 1 month, a sputum AFB smear and culture became negative and no additional M. szulgai were isolated during a 16-month treatment.

• Journal of Life Science
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• v.26 no.6
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• pp.711-720
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• 2016

To determine the degree of common genes and the phylogenetic relationships among genome-sequenced 680 prokaryotes, the similarities among 4,631 clusters of orthologous groups of protein (COGs)’ presence/ absence and gene content trees were analyzed. The number of COGs was in the range of 103–2,199 (mean 1377.1) among 680 prokaryotes. Candidatus Nasuia deltocephalinicola str. NAS-ALF, an obligate symbiont with insects, showed the minimum COG, while Pseudomonas aeruginosa PAO1, an opportunistic pathogen, represented the maximum COG. The similarities between two prokaryotes were 49.30–99.78 % (mean 72.65%). Methanocaldococcus jannaschii DSM 2661 (hyperthermophilic and autotrophic, Euryarchaeota phylum) and Mesorhizobium loti MAFF303099 (mesophilic and symbiotic, alpha-Proteobacteria class) had the minimum amount of similarities. As gene content may represent the potential for an organism to adapt to each habitat, this may represent the history of prokaryotic evolution or the range of prokaryotic habitats at present on earth. COG content trees represented the following. First, two members of Chloroflexi phylum (Dehalogenimonas lykanthroporepellens BL-DC-9 and Dehalococcoides mccartyi 195) showed a greater relationship with Archaea than other Eubacteria. Second, members of the same phylum or class in the 16S rRNA gene were separated in the COG content tree. Finally, delta- and epsilon-Proteobacteria were in different lineages with other Proteobacteria classes in neighbor-joining (NJ) and maximum likelihood (ML) trees. The results of this study would be valuable to identifying the origins of organisms, functional relationships, and useful genes.

• Korean Journal of Microbiology
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• v.50 no.4
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• pp.384-386
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• 2014

Pseudomonas aeruginosa is an opportunistic pathogen that inhabits various natural and artificial environments, such as pathogenesis, water, soil and air. They can cause serious problems, such as pathogenic infection. In this study, 220 colonies were isolated from water and soil environment that assumed to be P. aeruginosa using a membrane filter method based on International Organization for Standardization (ISO/NP 16266). Identification of the isolates was determined by physiobiochemical characteristics using newly modified ISO method which includes the resistance to 1,10 phenanthroline test. Only one of 220 presumed P. aeruginosa strains isolated from effluence water using a drain swab was determined as P. aeruginosa-positive by the ISO/NP 16266 method. Subsequently, the resistance to 1,10 phenanthroline test, which was newly proposed by ISO in 2014 and applied in this study, was considered as more precise and improvable method for identification of P. aeruginosa.

• Korean Journal of Microbiology
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• v.50 no.4
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• pp.360-367
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• 2014

Candida albicans is an opportunistic and the most prevalent fungal pathogen that can cause superficial and systemic infections in immunocompromised patients. C. albicans can promote the transition from budding yeast to filamentous form, generating biofilms. Infections associated with C. albicans biofilms are frequently resistant to conventional antifungal therapy. Therefore, the development of more effective antifungal drugs related with biofilm formation is required urgently. The roots of Rheum undulatum have been used for medicinal purposes in Korea and China traditionally. The aim of present study was to evaluate the effect of R. undulatum extract upon preformed biofilms of 12 clinical C. albicans isolates and the antifungal activities. Its effect on preformed biofilms was evaluated using XTT reduction assay, and metabolic activity of all tested strains was reduced significantly ($49.4{\pm}6.0%$) at 0.098 mg/ml R. undulatum. The R. undulatum extract blocked the adhesion of C. albicans biofilms to polystyrene surfaces, and damaged the cell membrane integrity of C. albicans which was analyzed by CFDA, AM, and propidium iodide double staining. It caused cell lysis which was observed by Confocal laser scanning and phase contrast microscope after propidium iodide and neutral red staining, respectively. Membrane permeability was changed as evidenced by crystal violet uptake. The data suggest that R. undulatum inhibits biofilm formation by C. albicans, which can be associated with the damage of the cell membrane integrity, the changes in the membrane permeability and the cell lysis of C. albicans.