• International Journal of Oral Biology
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• 제41권4호
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• pp.209-215
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• 2016

Chlorhexidine has long been used in mouth washes for the control of dental caries, gingivitis and dental plaque. Minimal inhibitory concentration (MIC) is the lowest concentration of an antimicrobial substance to inhibit the growth of bacteria. Concentrations lower than the MIC are called sub minimal inhibitory concentrations (sub-MICs). Many studies have reported that sub-MICs of antimicrobial substances can affect the virulence of bacteria. The aim of this study was to investigate the effect of sub-MIC chlorhexidine on biofilm formation and coaggregation of oral early colonizers, such as Streptococcus gordonii, Actinomyces naeslundii and Actinomyces odontolyticus. The biofilm formation of S. gordonii, A. naeslundii and A. odontolyticus was not affected by sub-MIC chlorhexidine. However, the biofilm formation of S. mutans increased after incubation with sub-MIC chlorhexidine. In addition, cell surface hydrophobicity of S. mutans treated with sub-MIC of chlorhexidine, decreased when compared with the group not treated with chlorhexidine. However, significant differences were seen with other bacteria. Coaggregation of A. naeslundii with A. odontolyticus reduced by sub-MIC chlorhexidine, whereas the coaggreagation of A. naeslundii with S. gordonii remained unaffected. These results indicate that sub-MIC chlorhexidine could influence the binding properties, such as biofilm formation, hydrophobicity and coaggregation, in early colonizing streptococci and actinomycetes.

• International Journal of Oral Biology
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• 제40권1호
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• pp.35-39
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• 2015

Minimal inhibitory concentration (MIC) is the lowest concentration of antibiotics that inhibits the visible growth of bacteria. It has been reported that sub-MIC of antibiotics may result in morphological alterations, along with the biochemical and physiological changes in bacteria. The purpose of this study was to examine morphological changes of Aggregatibacter actinomycetemcomitans, after the treatment with sub-MIC metronidazole and penicillin. The bacterial morphology was observed with scanning electron microscope, after incubating with sub-MIC antibiotics. The length of A. actinomycetemcomitans was increased after the incubation with sub-MIC metronidazole and penicillin. Sub-MIC metronidazole and penicillin inhibited bacterial division and induced long filaments. Our study showed that metronidazole and penicillin can induce the morphological changes in A. actinomycetemcomitans.

• International Journal of Oral Biology
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• 제40권4호
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• pp.189-196
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• 2015

Minimal inhibitory concentration (MIC) is the lowest antibiotic concentration that inhibits the visible growth of bacteria. Sub-minimal inhibitory concentration (Sub-MIC) is defined as the concentration of an antimicrobial agent that does not have an effect on bacterial growth but can alter bacterial biochemistry, thus reducing bacterial virulence. Many studies have confirmed that sub-MICs of antibiotics can inhibit bacterial virulence factors. However, most studies were focused on Gram-negative bacteria, while few studies on the effect of sub-MICs of antibiotics on Gram-positive bacteria. In this study, we examined the influence of sub-MICs of doxycycline, tetracycline, penicillin and amoxicillin on biofilm formation and coaggregation of Streptococcus gordonii, Streptococcus mutans, Actinomyces naeslundii, and Actinomyces odontolyticus. In this study, incubation with sub-MIC of antibiotics had no effect on the biofilm formation of S. gordonii and A. naeslundii. However, S. mutans showed increased biofilm formation after incubation with sub-MIC amoxicillin and penicillin. Also, the biofilm formation of A. odontolyticus was increased after incubating with sub-MIC penicillin. Coaggregation of A. naeslundii with S. gordonii and A. odontolyticus was diminished by sub-MIC amoxicillin. These observations indicated that sub-MICs of antibiotics could affect variable virulence properties such as biofilm formation and coaggregation in Gram-positive oral bacteria.

• International Journal of Oral Biology
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• 제39권2호
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• pp.115-120
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• 2014

Minimal inhibitory concentration (MIC) is the lowest concentration of antibiotics that inhibits the visible growth of a microorganism. It has been reported that sub-MIC of antibiotics may result in morphological alterations along with biochemical and physiological changes in bacteria. The purpose of this study was to examine morphological changes of periodontal pathogens after treatment with sub-MIC antibiotics. Aggregatibacter actinomycetemcomitans, Fusobacterium nucleatum, and Porphyromonas gingivalis were used in this study. The MIC for amoxicillin, doxycycline, metronidazole, penicillin, and tetracycline were determined by broth dilution method. The bacterial morphology was observed with bright field microscope after incubating with sub-MIC antibiotics. The length of A. actinomycetemcomitans and F. nucleatum were increased after incubation with metronidazole; penicillin and amoxicillin. P. gingivalis were increased after incubating with metronidazole and penicillin. However, F. nucleatum showed decreased length after incubation with doxycycline and tetracycline. In this study, we observed that sub-MIC antibiotics can affect the morphology of periodontal pathogens.

• 대한의생명과학회지
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• 제30권2호
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• pp.96-99
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• 2024

In vitro antimicrobial activities of hot water extracts of Chamaecyparis obtuse, for clinical metallo-β-lactamase-Producing Pseudomonas aeruginosa (MBLPA.) was compared to commonly used conventional antimicrobial agents. All MBLPA was susceptible to colistin or amikacin, but also to imipenem 88.6%, meropenem 100%, piperacillin 85.7%, ceftazidime 97.1%, gentamicin 97.1%, and ciprofloxacin 100% were non-susceptible. MIC range to imipenem, meropenem, cefotaxime, ceftazidime, gentamicin, and ciprofloxacin for MBLPA were each 1 - >128 ㎍/mL, 4 - >128 ㎍/mL, 4 - >128 ㎍/mL, 8 - >128 ㎍/mL, 4 - >128, and 2- >128 ㎍/mL. MIC range to aztreonam for MBLPA were 1 - 128 ㎍/mL. MIC₉₀ to imipenem, meropenem, cefotaxime, ceftazidime, gentamicin, and ciprofloxacin for MBLPA were each 32 ㎍/mL, >128 ㎍/mL, >128 ㎍/mL, >128 ㎍/mL, >128 ㎍/mL, and 128 ㎍/mL. MIC₉₀ to colistin and amikacin were each 1 ㎍/mL and 64 ㎍/mL. The hot water extracts of C. obtuse leaf had the lowest MIC range (0.25 - >0.5 μL/mL), MIC₅₀ (>0.5 μL/mL), and MIC₉₀ (>0.5 μL/mL) of the clinical MBLPA tested, and it was possible more potent than various conventional antimicrobial agents for MBLPA infection patients. Therefore, it suggested the possibility of using extract components of C. obtuse or their derivatives to treat MBLPA infection patients.

• 대한의생명과학회지
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• 제30권1호
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• pp.32-35
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• 2024

In vitro antimicrobial activities of hot water extracts of Chamaecyparis obtuse, for methicillin-resistant Staphylococcus aureus (MRSA) was compared to commonly used conventional antimicrobial agents. All MRSA was susceptible to linezolid or vancomycin, but also to erythromycin. MIC range and MIC₉₀ to erythromycin, clindamycin, levofloxacin, tetracycline for MRSA were each 4 ㎍/mL, 2 ~ >128 ㎍/mL, ≤0.06 ~ >128 ㎍/mL, 0.25 ~ >128 ㎍/mL, 0.25~64 ㎍/mL and 4 ㎍/mL, .128 ㎍/mL, >128 ㎍/mL, >128 ㎍/mL, 64 ㎍/mL. The hot water extracts of leaf of C. obtuse had the lowest MIC range, MIC₅₀, and MIC₉₀ (0.125 µL/mL) for the MRSA tested, and it was possible more potent than various conventional antimicrobial agents. Screen antibacterial drug candidate with high antibacterial activity such as derivatives of C. obtuse leaf extract such as terpinen-4-ol or using combined therapy with commercialized antibacterial agents will likely be helpful in treating refractory MRSA infections.

• Journal of Power Electronics
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• 제14권6호
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• pp.1281-1292
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• 2014

Photovoltaic (PV) solar systems with series-connected module integrated converters (MICs) are receiving increased attention because of their ability to create high output voltage while performing local maximum power point tracking (MPPT) control for individual solar panels, which is a solution for partial shading effects in PV systems at panel level. To eliminate the partial shading effects in PV system more effectively, sub-MICs are utilized at the cell level or grouped cell level within a PV solar panel. This study presents the results of a series-output-connection MPPT (SOC-MPPT) controller for sub-MIC architecture using a single sensor at the output and a single digital MPPT controller (sub-MIC SOC-MPPT controller and architecture). The sub-MIC SOC-MPPT controller and architecture are investigated based on boost type sub-MICs. Experimental results under steady-state and transient conditions are presented to verify the performance of the controller and the effectiveness of the architecture.

• International Journal of Oral Biology
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• 제30권2호
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• pp.59-63
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• 2005

Postantibiotic effects (PAE) refer to suppression of the bacterial growth following limited periods of exposure to an antibiotic and subsequent to the removal of the antibiotic agent. Fusobacterium nucleatum and Porphyromonas gingivalis are Gram-negative anaerobic bacteria associated with several periodontal diseases. In this study, postantibiotic effects (PAE), postantibiotic sub-MIC effect (PA SME) and sub-MIC effect (SME) of antibiotics on F. nucleatum ATCC 25586 and P. gingivalis W50 were investigated. The PAE was induced by 10X the MIC of antibiotic and antibiotic was eliminated by washing. The PA SMEs were studied by addition of 0.1, 0.2 and 0.3X MICs during the postantibiotic phase of the bacteria, and the SMEs were studied by exposition of the bacteria to antibiotic at the sub-MICs only. Amoxicillin, doxycycline and tetracycline induced PAE for F. nucleatum ATCC 25586 and P. gingivalis W50. But metronidazole and penicillin induced PAE for only F. nucleatum ATCC 25586. Metronidazole and doxycycline induced PA SME and SME for both species of anaerobic bacteria used in this study. The PA SME values for both strains were substantially longer than the SME values. The present study showed the existence of PAE, PA SME and SME for various antibiotics against F. nucleatum ATCC 25586 and P. gingivalis W50.

• 생명과학회지
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• 제30권3호
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• pp.278-284
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• 2020

목련은 항산화효과와 진정작용과 같은 다양한 효능을 가진 것으로 알려져 있다. 본 연구에서는 목련 에센셜오일의 항균 활성 및 항염증 활성을 검증하고자 한다. 목련 에센셜 오일은 증류법으로 추출한 것을 사용하였으며, 항균 활성은 S. aureus와 E. coli, P. aeruginosa에 대하여 paper disk diffusion법과 최소저해농도(minimum inhibitory concentration, MIC) 값을 측정하여 확인하였다. 목련 에센셜 오일은 S. aureus 균주에 대하여 18 mm의 clear zone형성과 0.25 mg/ml의 MIC 값을 나타내는 우수한 항균효과를 보였다. P. aeruginosa 균주와 E. coli 균주는 clear zone 형성이 각각 14 mm와 17 mm로 나타났다. 또한, MIC값은 각각 1 mg/ml와 0.5 mg/ml로 측정되었다. 항염증 활성은 LPS 유도된 RAW264.7 세포에서 nitric oxide (NO)와 PGE₂의 생성억제율을 조사하였다. 목련 에센셜 오일, 500 ㎍/ml의 농도에서 RAW264.7세포에 대한 세포 독성은 나타내지 않았지만, NO (37.7%)와 PGE₂ (24.0%)억제를 보였다. GC-MS를 이용하여 목련 에센셜 오일을 분석하였다. 목련 에센셜 오일의 3 가지 주요 방향제 성분은 3-carene (77.07%), β-elemene (6.92%) 및 caryphyllene (2.86%)로 분석되었다. 이러한 결과는 목련 에센셜 오일이 항균 및 항염증 효과를 갖는 화장품 기능성 물질로서 잠재력을 가지고 있음을 시사한다.

• Journal of Veterinary Science
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• 제22권6호
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• pp.41.1-41.14
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• 2021

Background: Our previously prepared ceftiofur (CEF) hydrochloride oily suspension shows potential wide applications for controlling swine Streptococcus suis infections, while the irrational dose has not been formulated. Objectives: The rational dose regimens of CEF oily suspension against S. suis were systematically studied using a pharmacokinetic-pharmacodynamic model method. Methods: The healthy and infected pigs were intramuscularly administered CEF hydrochloride oily suspension at a single dose of 5 mg/kg, and then the plasma and pulmonary epithelial lining fluid (PELF) were collected at different times. The minimum inhibitory concentration (MIC), minimal bactericidal concentration, mutant prevention concentration (MPC), post-antibiotic effect (PAE), and time-killing curves were determined. Subsequently, the area under the curve by the MIC (AUC_0-24h/MIC) values of desfuroylceftiofur (DFC) in the PELF was obtained by integrating in vivo pharmacokinetic data of the infected pigs and ex vivo pharmacodynamic data using the sigmoid E_max (Hill) equation. The dose was calculated based on the AUC_0-24h/MIC values for bacteriostatic action, bactericidal action, and bacterial elimination. Results: The peak concentration, the area under the concentration-time curve, and the time to peak for PELF's DFC were 24.76 ± 0.92 ㎍/mL, 811.99 ± 54.70 ㎍·h/mL, and 8.00 h in healthy pigs, and 33.04 ± 0.99 ㎍/mL, 735.85 ± 26.20 ㎍·h/mL, and 8.00 h in infected pigs, respectively. The MIC of PELF's DFC against S. suis strain was 0.25 ㎍/mL. There was strong concentration-dependent activity as determined by MPC, PAE, and the time-killing curves. The AUC_0-24h/MIC values of PELF's DFC for bacteriostatic activity, bactericidal activity, and virtual eradication of bacteria were 6.54 h, 9.69 h, and 11.49 h, respectively. Thus, a dosage regimen of 1.94 mg/kg every 72 h could be sufficient to reach bactericidal activity. Conclusions: A rational dosage regimen was recommended, and it could assist in increasing the treatment effectiveness of CEF hydrochloride oily suspension against S. Suis infections.