• 한국동물위생학회지
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• 제44권4호
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• pp.247-256
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• 2021

The recombinant lysozyme-HJL34 proteins were expressed and purified using commercial Escherichia (E.) coli expression system. Stx2e⁺ F18⁺ E. coli, Actinobacillus pleuropneumoniae (APP), Streptococcus (S.) suis, and Clostridium (C.) perfringens strains were isolated from pigs. The minimum inhibitory concentrations (MICs) of the recombinant lysozyme-HJP34 proteins were examined by means of the microtiter plate method, according to the NCCLS recommendations. The possibility of its as the alternatives to antibiotics was tested in piglets. The MICs were determined as 75 ㎍/mL, 300 ㎍/mL, 75 ㎍/mL, 35.5 ㎍/m against Stx2e⁺ F18⁺ E. coli, APP, S. suis, C. perfringens, respectively. A total of 25 piglets were divied 5 groups. The piglets in group A~C were fed with commercial feed and those in groups D, E were fed with commercial feedstuff. All piglets in groups B~E were challenged with virulent Stx2e⁺ F18⁺ E. coli, APP, S. suis strains. Groups C and D were treated with antimicrobial from 24 h after challenge. All piglets in group B died within 3 days after challenge. Among 5 piglets in groups C and D piglets, 80% survived after challenge. Among group E piglets, 60% were alive until the end of this study. Therefore, this study indicates that recombinant lysozyme-HJP34 proteins is a suitable possibility as a feed additive for reduction of diseases by bacterial pathogens in piglet feed.

• Journal of Veterinary Science
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• 제25권1호
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• pp.12.1-12.10
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• 2024

Background: Staphylococcus aureus and S. pseudintermedius are the major etiological agents of staphylococcal infections in humans, livestock, and companion animals. The misuse of antimicrobial drugs has led to the emergence of antimicrobial-resistant Staphylococcus spp., including methicillin-resistant S. aureus (MRSA) and methicillin-resistant S. pseudintermedius (MRSP). One novel therapeutic approach against MRSA and MRSP is a peptide nucleic acid (PNA) that can bind to the target nucleotide strands and block expression. Previously, two PNAs conjugated with cell-penetrating peptides (P-PNAs), antisense PNA (ASP)-cmk and ASP-deoD, targeting two essential genes in S. aureus, were constructed, and their antibacterial activities were analyzed. Objectives: This study analyzed the combined antibacterial effects of P-PNAs on S. aureus and S. pseudintermedius clinical isolates. Methods: S. aureus ATCC 29740 cells were treated simultaneously with serially diluted ASP-cmk and ASP-deoD, and the minimal inhibitory concentrations (MICs) were measured. The combined P-PNA mixture was then treated with S. aureus and S. pseudintermedius veterinary isolates at the determined MIC, and the antibacterial effect was examined. Results: The combined treatment of two P-PNAs showed higher antibacterial activity than the individual treatments. The MICs of two individual P-PNAs were 20 and 25 µM, whereas that of the combined treatment was 10 µM. The application of a combined treatment to clinical Staphylococcus spp. revealed S. aureus isolates to be resistant to P-PNAs and S. pseudintermedius isolates to be susceptible. Conclusions: These observations highlight the complexity of designing ASPs with high efficacy for potential applications in treating staphylococcal infections in humans and animals.

• Archives of Pharmacal Research
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• 제19권4호
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• pp.317-320
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• 1996

The time-kill curves of LB20304, a novel fluoroquinolone that has potent antibacterial activity against gram-positve and gram-negative bacteria, were calculated at the concentrations of 1/4-, 1/2-, 1-, 2- and 4-times the MIC against Staphylococcus aureus 77, Escherichia coli 3739E, Pseudomonas aeruginosa 1912E. The bactericidal activity of LB20304 for these strains was very rapid and comparable to that of ciprofloxacin. LB20304 produced a decrease in the $log_10$ CFU per milliliter of${\geq}$3 within 2 h at 4-times the MIC for all strains and consitently prevented regrowth of bacteria after 24 h of incubation. The MBCs (Minimal Bactericidal Concentration) of LB20304 against test organisms were equal to or at most four-times higher than the MICs.

• Natural Product Sciences
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• 제11권3호
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• pp.160-164
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• 2005

The effects of Cymbopogon citratus essential oil (Lemongrass oil) and its main component, citral (84.30%), on antibiotic-susceptible and -resistant strains of Salmonella enteritidis and S. typhimurium were assessed. C. citratus oil and citral significantly inhibited all strains of the two Salmonella species examined, with minimum inhibiting concentrations (MICs) ranging from 0.5 mg/ml to 8.0 mg/ml. The combined effects of C. citratus oil and citral (84.30%) were evaluated using a checkerboard microtiter assay. Essential oil fractions of C. citratus and citral exhibited strong synergistic or additive effects with streptomycin or kanamycin against S. typhimurium strains with fractional inhibitory concentration (FIC) indices in the range of 0.28 to 1.00. In conclusion, a combination of streptomycin and lemongrass oil or its main component, citral, may be useful for reducing the minimum effective dose of antibiotic required for the treatment of resistant S. typhimurium infections.

• Natural Product Sciences
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• 제14권2호
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• pp.138-142
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• 2008

The composition of essential oils from Chrysanthemum zawadskii var. latilobum and C. indicum were analyzed and compared. The results of gas chromatography-mass spectrometry revealed there were distinctly different compositional patterns between C. zawadskii var. latilobum and C. indicum essential oils. The combinatorial effect of the oil of C. zawadskii var. latilobum and C. indicum, with various antibiotics was assessed against antibiotic-susceptible and -resistant strains of Staphylococcus aureus and Streptococcus pneumoniae. The essential oil fraction significantly inhibited most of the tested antibiotic-susceptible and -resistant strains of S. pneumoniae, with minimum inhibiting concentrations (MICs) ranging from 0.5 to 4.0 mg/ml. The fractional inhibiting concentration indices (FICIs) of the oils when combined with antibiotics against S. aureus and S. pneumoniae ranged from 0.26 to 0.75, and showed synergistic or additive effects.

• Journal of electromagnetic engineering and science
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• 제12권1호
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• pp.32-36
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• 2012

In this paper, we present a novel algorithm for detecting a bonded channel in a cognitive radio network where channel bonding is allowed for a higher data rate. The envelope detection algorithm is proposed to distinguish the center frequency of the received signal in order to determine whether the signal is transmitted by a primary user occupying a single channel or a secondary user occupying more than two channels when the channel is in use.

• 한국자동차공학회논문집
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• 제5권5호
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• pp.132-139
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• 1997

It is difficult for most of passenger cars to attach various types of suspensions. The modular experimental vehicle, which is designed to exchange suspension systems, has been developed to evaluate the effect of design changes of a suspension upon ride and handling characteristics of a vehicle. In order to enable the assemblage between modules, the experimental vehicle design is based on a space frame construction through finite element analysis. Moreover, module frames and brackets are designed using three-dimensional solid modeler to check the interference between each part of a vehicle. Steady-state and transient road tests were performed. Multibody dynamic model and simplified linear vehicle model are made to compare with the tests. The results of simulations and tests show the performance and validity of this experimental vehicle.

• 한국미생물·생명공학회지
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• 제25권3호
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• pp.335-337
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• 1997

In this study, we show a convenient MTT assay for detect the susceptibility of yeast-like form of Trichosporon beigelii against antifungal agents. This assay was developed based on mitocondrial respiration by determining reduction of 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) to formazan. Cells of T beigelii are seeded into 96-well microtiter plates, and antifungal agents, amphotericin B, magainin and CA-ME hybrid peptide were added with various concentrations. After 24 hr incubation, MTT was added, then incubations were continued for 4 hr. Formazan formation was quantified photometrically after extraction of the formazan with acid sodium dodesyl sulfate (SDS). From this assay, we could obtained MICs of antifungal agents against T. beigelii. The presented method can easily be used as an effective methods to assess the antiftingal action of various agents on yeasts with minimal amounts of antifungal agents.

• Journal of Microbiology and Biotechnology
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• 제12권6호
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• pp.1017-1021
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• 2002

A novel antibacterial metabolite, ARK42, was elated from a xerophilic fungal strain K42, and Identified as Aspergillus repens based on its morphological characteristics. The metabolite exhibited antibacterial activities towards Staphylococcus aureus, Bacillus cereus, and Pseudomonas aeruginosa, with MICs of 25, 12.5, and $3.125{\mu}g/ml$, respectively, and killed Pseudomonas aeruginosa with minimal bactericidal concentration (MBC) of $12.5{\mu}g/ml$. Furthermore, anticancer activities were demonstrated against human colon cancer DLD- 1 and lung cancer LXFL529 cells with an $IC_50$ of 10 and $1{\mu}g/ml$, respectively.

• 한국미생물·생명공학회지
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• 제27권5호
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• pp.354-358
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• 1999

In order to know the antifungal characteristics of saturated fatty acids having 6 to 12 carbons, their minimum inhibitory concentrations (MICs) and minimum fungicidal concentrations (MFCs) were estimated against Saccharomyces cerevisiae. Fatty acids from C6 to C11 exhibited increasing activity with chain length, but C12 fatty acid did not show activity at all. In relation to antifungal modes of actions, fatty acids investigated showed on inhibitory activity toward the plasma membrane H+-ATPase of Saccharomyces cerevisiae. Their inhibitions to the glucose-induced acidification and ATP hydrolysis caused by the proton pump were found to be in common wiht antifungal activities. At the test concentration of 1mM, hexanoic acid (C6) showed the lowest inhibition of about 30%, while undecanoic acid(C11) showed the strongest inhibition of over 90%. In addition, as seen with antifungal activity, the inhibitory activity of dodecanoic acid (C12) was suddenly reduced to less than 50%.