• ALGAE
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• v.29 no.4
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• pp.249-265
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• 2014

As with land crops, cultivated algae are affected by various diseases ranging from large outbreaks of a disease to chronic epiphytes, which may downgrade the value of the final product. The recent development of intensive and dense mariculture practices has enabled some new diseases to spread much faster than before. A new disease is reported almost every year, and the impact of diseases is expected to increase with environmental change, such as global warming. We observed the incidence of diseases in two Pyropia sea farms in Korea from 2011 to 2014, and estimated the economic loss caused by each disease. Serious damage is caused by the oomycete pathogens, Pythium porphyrae and Olpidiopsis spp., which decreased the productivity of the Pyropia sea farms. In Seocheon sea farms, an outbreak of Olpidiopsis spp. disease resulted in approximately US $1.6 million in loss, representing approximately 24.5% of total sales during the 2012-2013 season. The damage caused by green-spot disease was almost as serious as oomycete diseases. An outbreak of green-spot disease in the Seocheon sea farms resulted in approximately US $1.1 million in loss, representing 10.7% of total sales in the 2013-2014 season in this area. However, the causative agent of green-spot disease is still not confirmed. "Diatom felt" is regarded as a minor nuisance that does not cause serious damage in Pyropia; however, our case study showed that the economic loss caused by "diatom felt" might be as serious as that of oomycete diseases. Bacteria and cyanobacteria are indigenous members of epiphytic microbial community on Pyropia blades, but can become opportunistic pathogens under suitable environmental conditions, especially when Pyropia suffers from other diseases. A regular acid wash of the Pyropia cultivation nets is the most common treatment for all of the above mentioned diseases, and represents approximately 30% of the total cost in Pyropia sea farming. However, the acid wash is ineffective for some diseases, especially for Olpidiopsis and bacterial diseases.

• Tuberculosis and Respiratory Diseases
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• v.60 no.5
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• pp.571-575
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• 2006

Mycobacterium avium has been traditionally described as an opportunistic organism that causes disseminated disease in human immunodeficiency virus-positive patients and acts as a pulmonary pathogen in patients with underlying lung diseases such as chronic obstructive pulmonary disease or previously treated tuberculosis. Infections caused by M. avium in immunocompetent hosts usually manifest as 2 distinct subtypes, the upper lobe cavitary form and the nodular bronchiectatic form. However endobronchial lesions due to M. avium infections in immunocompetent host are reasonably rare, and there are no reports of this condition in Korea. We report here a case of endobronchial lesions involved in an M. avium infection in an immunocompetent 21 year-old female patient with no preexisting lung disease.

• Parasites, Hosts and Diseases
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• v.30 no.4
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• pp.277-282
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• 1992

Pneumocystis carinii (Pc) is an important opportunistic pathogen of immune compromised hosts, and is known to infect various animals. The present study observed the infection status of 6 mammals and 3 strains of albino rats with Pc after suppression of their immunity. Methyl-prednisolone was injected once a week and tetracycline was supplied with water for 5 to 21 weeks. Hamsters, guinea pigs, rabbits, dogs, cats and pigs were negative by impression smear, and only the rats were found infected by Pc. All of the three strains of rats, Sprague-Dawley(SD), Wistar(W) and Fisher(F), were infected by Pc but W rats showed heavier degree of infection in earlier period than F or SD rats. The present findings suggest that W rat is the best among the animals used in the present study for production of Pc.

• The Korean Journal of Mycology
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• v.39 no.1
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• pp.85-87
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• 2011

The opportunistic human pathogen Candida albicans has the ability to convert from yeast-form to pseudohyphal or true hyphal form. The morphological transition is considered as an important virulence factor, because the decrease or lack in dimorphism causes the reduction of virulence. Our previous study revealed that the disruption of dual specificity kinase gene caused the reduction of dimorphism in C. albicans. Therefore we tested the effect of dual specificity kinase in virulence using mouse model. The mean survival time for kinase-defective strains was about 15 days in comparison with those of wild-type, 3.9 days. Moreover the fungal burden on kidneys for kinase-defective strains was decreased by ten-fold than that for wild-type. These results suggest possible involvement of dual specificity kinase in a novel signal transduction pathway for morphological transition and virulence of C. albicans.

• Journal of Microbiology and Biotechnology
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• v.15 no.6
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• pp.1197-1206
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• 2005

Vibrio vulnificus is an opportunistic pathogen that causes a septicemia and expresses numerous virulence factors, in which luxS and smcR are genes encoding for components responsible for quorum-sensing regulation. In the present study, null mutants were constructed with lesions in each or both of these two genes from the V. vulnificus Vv$\Delta$Z strain, which is a lacZ$^{-}$ and chloramphenicol/streptomycin-resistant derivative of the wild-type ATCC29307 strain, and their phenotypes related to virulence were compared with those of the parental cells. $LD_{50}$ and histopathological findings of luxS-, smcR-, or luxS- smcR- deficient mutant were not different from those of the parent strain, a lacZ-deficient streptomycin-resistant strain in mice. However, time of death in mice was delayed, and numbers of bacteria survived in bloodstream after intraperitoneal injection in mice were decreased by mutation, especially luxS and smcR double mutant (VvSR$\Delta$ZSR). These phenomena were supported by increased serum sensitivity and delayed bacterial proliferation in both murine blood and iron-restricted medium. These results suggest that the luxS and luxR homologous genes in V. vulnificus could playa role in bacterial survival in host by enhancing proliferation and adjusting to changed environment.

• Journal of Microbiology and Biotechnology
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• v.19 no.9
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• pp.932-945
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• 2009

Several species of Gram-positive bacteria have cell wall peptidoglycan (syn. murein) in which not all of the sugar moieties are N-acetylated. This has recently been shown to be a secondary effect, caused by the action of a peptidoglycan N-acetylglucosamine deacetylase. We have found that the opportunistic pathogen Listeria monocytogenes is unusual in having three enzymes with such activity, two of which remain in the cytoplasm. Here, we examine the enzyme (PgdA) that crosses the cytoplasmic membrane and is localized in the cell wall. We purified a hexa-His-tagged form of PgdA to study its activity and constructed a mutant devoid of functional Lmo0415 (PgdA) protein. L. monocytogenes PgdA protein exhibited peptidoglycan N-acetylglucosamine deacetylase activity with natural substrates (peptidoglycan) from both L. monocytogenes and Escherichia coli as well as the peptidoglycan sugar chain component N-acetylglucosamine, but not with N-acetylmuramic acid. As was reported recently [6], inactivation of the structural gene was not lethal for L. monocytogenes nor did it affect growth rate or morphology of the cells. However, the pgdA mutant was more prone to autolysis induced by such agents as Triton X-100 and EDTA, and is more susceptible to the cationic antimicrobial peptides (CAMP) lysozyme and mutanolysin, using either peptidoglycan muramidases or autolysis-inducing agents. The pgdA mutant was also slightly more susceptible than the wild-type strain to the action of certain beta-lactam antibiotics. Our results indicate that protein PgdA plays a protective physiological role for listerial cells.

• Fisheries and Aquatic Sciences
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• v.5 no.3
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• pp.145-149
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• 2002

The effects of pH, temperature and various inhibitors on the proteolytic activity of the cell lysate of Uronema marium were investigated using colorimetric and substrate gel electro­phoretic methods. The cell lysate of U. marinum showed proteolytic activity over a wide range of pH, and pH optima ranged from pH 5 to 7. The proteolytic activity was increased according to a rise of temperature but decreased at $40^{\circ}$. The proteolytic activity of the parasite lysate was significantly inhibited by protease inhibitors including trans-epoxysuccinyl -L-leucylamido-(4-guanidino) butane (E-64), pepstatin A, phenyl-methanesulfonyl fluoride(PMSF), and ethylenediamine-tetraacetic acid (EDTA). Preincubation of the lysate with E-64 showed the maximum inhibition of the caseionolytic activity. Four protease bands (152, 97, 67 and 40 kDa) were detected by gelatin SDS-PAGE. Significant inhibition of caseinolytic activity and complete abolition of a 152 kDa band in gelatin SDS-PAGE by EDTA indicated that the cell lysate of U. marinum had a metalloprotease Another three proteolytic bands were inhibited by E64, a cysteine protease inhibitor. Preincubation of the cell lysate with pepstatin or PMSF had no effects on the protease bands.

• Journal of dental hygiene science
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• v.15 no.4
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• pp.383-392
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• 2015

Dental chair unit (DCU) is the most essential equipment for the dental treatment in dentistry. DCU output water is used for various applications during dental treatment. DCU output water must be clean at the same level as drinking water since patients and dental staff are regularly exposed to water and aerosols generated from the DCU. Many studies demonstrated that DCU output water is frequently contaminated with microorganisms including opportunistic pathogen such as Legionella and Pseudomonas species. Thus, DCU output water may be a potential source of infection. In order to reduce microbial contamination levels in DCU output water, periodic management and continuous disinfection are necessary. Currently, there are a variety of disinfection methods for managing DCU output water and its efficacy is also diverse. We reviewed the level of microbial contamination, clinical implications of contaminated DCU output water and the various DCU disinfection methods.

• Korean Journal of Clinical Laboratory Science
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• v.45 no.1
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• pp.21-25
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• 2013

Acinetobacter baumannii is an aerobic, gram-negative and glucose-non-fermenting bacterium, which has emerged as a serious opportunistic pathogen. Many clinical microbiology laboratories use the Vitek 2 system for the routine antimicrobial susceptibility testing process, including testing on A. baumannii isolates. However, in case of amikacin, it is now recommended to perform additional antimicrobial susceptibility testing for A. baumannii strains due to the relatively lower minimum inhibitory concentration (MIC) in the Vitek 2 system compared to conventional reference methods. In our study, we assessed MIC for amikacin susceptibility testing of A. baumannii isolates in the Vitek 2 system, the agar dilution, Etest, and disk diffusion method. We collected 40 gentamicin-resistant, A. baumannii strains (amikacin MIC by Vitek 2:${\leq}2{\mu}g/mL$, 2 isolates; $4{\mu}g/mL$, 34 isolates; $8{\mu}g/mL$, 4 isolates) from a University hospital and compared the Vitek 2 system to other reference methods for testing susceptibility to amikacin. The Vitek 2 system showed major errors in all of the 40 isolates, yielding a low MIC. The results of our study strongly suggested that the Vitek 2 system was not a reliable method to test the MICs of gentamicin; ranging from ${\geq}16{\mu}g/mL$ for amikacin susceptibility. Other tests, such as agar dilution, Etest, or disk diffusion methods, should be paralleled to determine the MIC of amikacin in A. baumannii.

• The Journal of the Korean Society for Microbiology
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• v.16 no.1
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• pp.19-28
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• 1981

The Pseudomonas infection has been increased in incidence and suspected as a cause of opportunistic pathogen. Protease and elastase produced by Pseudomonas aeruginosa are reported to be closely associated with pathogenicity of Pseudomonas aeruginosa. We examined, in this work, the relationship between production of exoenzyme of Pseudomonas aeruginosa and susceptibility to antimicrobial agents in view of possible application to the management of Pseudomonas infection. 1. In 295 Pseudomonas aeruginosa isolated from clinical specimens, 34.6% were from pus, 20.7% from sputum, 15.6% from wound including burn sites and 12.9% from urine. 2. Distribution of protease and elastase production by clinically isolated Pseudomonas aeruginosa, showed that protease and elastase producing strains were 83.1%, protease producing strains were 7.5%, elastase producing strains were 2.0%, and non producing strains were 7.5%. 3. MIC(minimum inhibitory concentration) peak for tetracycline and chloramphenicol were observed at 25mcg/ml and 200mcg/ml respectively, but there were no Pseudomonas aeruginosa which correspond to MIC peak, 6.25mcg/ml. Gentamicin of aminoglycosides was highly susceptible to Pseudomonas aeruginosa clinically isolated from pus, sputum and wound sites, but susceptible to isolates from nasal discharge and urine. Regarding MIC peak of carbenicillin, 100mcg/ml, 81.8% of Pseudomonas aeruginosa were from urine, 54.8% from wound including burn sites, 52.7% from pus, and 50.8% from sputum. 4. Enzyme producing strains showed no susceptibility to kanamycine and carbenicillin at low concentration, but protease producing strains tend to resistant to antimicrobial agents.