• Archives of Pharmacal Research
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• v.11 no.3
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• pp.218-224
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• 1988

The preparation of Clostridium butyricum is used as a normalizing agent for human intestinal flora. When the microbe is simultaneously used with rifampicin, it is inactivated by the antibiotic. To develop rifampicin-resistant mutants, rifampicin-sensitive strain Miyairi II 588 of C. butyricum was treated with nitrosoguanidine (NTG). To ensure stable resistance to rifampicin, we examined whether the resistance was plasmid-mediated or chromosome-mediated. It was found that the resistance of four mutant strains was not mediated by its inherent plasmid, but by the chromosomal mutation. These strains were examined for the susceptibility and resistance to other antituberculosis agents and antibiotics. The results showed that these mutants were resistant to the high concentration of the antituberculosis agents.

• Journal of Oral Medicine and Pain
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• v.45 no.1
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• pp.17-21
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• 2020

Osteomyelitis of the jaw infected with Coagulase-Negative Staphylococci (CNS) is rarely reported in the Oral and Maxillofacial Region. Staphylococcus is a part of the normal body flora, but it may be cause severe infections and CNS are often described as the important pathogens in nosocomial infections. Although many studies on prevalence and antibiotics of Staphylococcus aureus have been done, but many of these studies focus only on Methicillin-resistant S. aureus and not on methicillin-resistant coagulase-negative Staphylococci (MRCNS). There was a less study about CNS or MRCNS infections in the Oral and Maxillofacial Region. This report describes a case of a 41-year-old male patient who developed osteomyelitis caused by MRCNS on condyle after open reduction and internal fixation and suggests guideline for the prevention of postoperative infection and appropriate recommendation for treatment and control.

• Natural Product Sciences
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• v.23 no.4
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• pp.286-290
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• 2017

Multidrug-resistant Acinetobacter baumannii and Pseudomonas aeruginosa are highly dangerous nosocomial pathogens, cause the symptoms of skin infections, pressure sores, sepsis, blood stream and wound infections. Unfortunately, these pathogens are immune to the most common antibiotics, such as, carbapenem, aminoglycoside and fluoroquinolone. Therefore, it is imperative that new and effective antibiotics be developed. In the present study, the antimicrobial effects of Aloe vera MAP (modified Aloe polysaccharide) on Staphylococcus aureus and Bacillus subtilis, Escherichia coli and Enterobacter aerogenes, and clinical Pseudomonas aeruginosa and clinical Acinetobacter baumannii were comprehensibly investigated. Prior to the growth inhibition effect measurement and antibiotic disc diffusion assay on gram-positive and gram-negative bacteria and selected multidrug-resistant Pseudomonas aeruginosa and Acinetobacter baumannii, antimicrobial resistance screening was performed for the multidrug-resistant bacteria obtained from clinical isolates. The results for showed the Aloe vera MAP had a concentration-dependent effect on all of examined bacteria, particularly on Pseudomonas aeruginosa. Anti-inflammatory and anti-oxidant experiments were also performed dose dependently effects to confirm the beneficial physiological effects of Aloe vera MAP.

• Microbiology and Biotechnology Letters
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• v.51 no.3
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• pp.293-295
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• 2023

Linezolid, the first oxazolidinone introduced into human clinical use, has become a last resort antibiotic in treatment of serious infections caused by Gram-positive pathogens, including methicillin-resistant staphylococci and vancomycin-resistant enterococci. Although oxazolidinones are strictly prohibited for use in food-producing animals, occurrence of linezolid-resistant staphylococci has recently been reported in livestock farms in Korea. Here, we report the complete genome sequence of an optrA-positive linezolid-resistant Staphylococcus rostri strain PJFA-333 isolated from a pig farm in Korea.

• Food Science and Biotechnology
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• v.16 no.3
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• pp.470-476
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• 2007

To evaluate the vancomycin resistance of Enterococcus spp. (VRE) from Saengsik and Sunsik, Enterococcus were isolated and identified from 25 Saengsik and 35 Sunsik samples, and resistance of Enterococcus to other antibiotics was also assessed. Thirty nine Enterococcus, 16 strains from Saengsik, and 23 strains from Sunsik, were ultimately isolated. The most frequently collected Enterococcus isolates in Saengsik were E. casseliflavus and E. hirae, and were E. casseliflavus and E. faecium in Sunsik. However, E. faecalis was not detected in those foods. Minimum inhibitory concentrations of vancomycin against the isolates were below $4\;{\mu}g/mL$ and no strains evidenced profound levels of resistance. The isolates were found to be susceptible to vancomycin with the exception of eight E. casseliflavus and three E. gallinarum. All Enterococcus isolates proved resistant to streptomycin and chloramphenicol. 23% of the isolates were resistant to penicillin; however, all of the isolates were sensitive to tetracycline. Six and 48%, respectively, of the strains from the Saengsik and Sunsik proved resistant to erythromycin. All of E. mundtii and E. hirae isolates from Saengsik, and 20% of E. gallinarum and E. casseliflavus isolates from Sunsik were found to be ampicillin-resistant. All of E. gallinarum, E. casseliflavus, and E. faecium were rifampin-resistant. The antibiotic resistances of Enterococcus were relatively low, and this low vancomycin resistance was similar to that evidenced by Enterococcus isolates obtained from the other foods. However, there may be a need for some review of the accepted antibiotics criteria for Enterococcus and VRE in ready-to-eat foods.

• Journal of Microbiology and Biotechnology
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• v.25 no.7
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• pp.1007-1014
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• 2015

Plectasin, the first defensin extracted from a fungus (the saprophytic ascomycete Pseudoplectania nigrella), is attractive as a prospective antimicrobial agent. The purpose of this study was to establish a bacterium-based production system and evaluate the antimicrobial activity of the resulting plectasin. A gene encoding plectasin, with the codon preference of Escherichia coli, was optimized based on its amino acid sequence, synthesized using genesplicing with overlap extension PCR, and inserted into the expression vector pGEX-4T-1. The fusion protein was expressed in the soluble fraction of E. coli and purified using glutathione Stransferase affinity chromatography. Plectasin was cleaved from the fusion protein with thrombin and purified by ultrafiltration. The purified plectasin showed strong, concentrationdependent antimicrobial activity against gram-positive bacteria, including antibiotic-resistant bacteria, especially penicillin-resistant Enterococcus faecium. This antimicrobial activity was equal to chemically synthesized plectasin and was maintained over a wide range of pH and temperatures. This soluble recombinant expression system in E. coli is effective for producing plectasin at a relatively lower cost, and higher purity and efficiency than prior systems, and might provide a foundation for developing a large-scale production system. Overall, plectasin shows potential as a novel, high-performance, and safe antibiotic for the treatment of refractory diseases caused by drug-resistant bacterial strains.

• The Journal of Internal Korean Medicine
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• v.34 no.3
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• pp.278-288
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• 2013

Objectives : Methicillin-resistant Staphylococcus aureus (MRSA) has a cephalosporin and beta-lactam antibiotic-resistant strains. MRSA is one of the major pathogens causing hospital infection and the isolation ratio of MRSA has gradually increased. Consequently, increased resistance to antibiotics is causing serious problems in the world. Therefore, there is a need to develop alternative antimicrobial drugs for the treatment of infectious diseases. Methods : The antibacterial activities of Ipyo-san were evaluated against 2 strains of MRSA and 1 standard Methicillin-susceptible staphylococcus aureus (MSSA) strain by using the disc diffusion method, minimal inhibitory concentrations (MIC) assay, colorimetric assay using MTT test, checkerboard dilution test and time-kill assay performed under dark. Results : The MIC of Ipyo-san water extract against S. aureus strains ranged from 1000 to $2,000{\mu}g/ml$, so we confirmed that it had a strong antibacterial effect. Also, the combinations of Ipyo-san water extract and conventional antibiotics exhibited improved inhibition of MRSA with synergy effect. We suggest that Ipyo-san water extract against MRSA has antibacterial activity so it has potential as alternatives to antibiotic agents. For the combination test, we used Triton X-100 (TX) and DCCD for measurement of membrane permeability and inhibitor of ATPase. As a result, antimicrobial activity of Ipyo-san water extract was affected by the cell membrane. Conclusions : We suggest that the Ipyo-san water extract lead the treatment of bacterial infection to solve the resistance and remaining side-effect problems that are the major weak points of traditional antibiotics.

• Journal of Microbiology and Biotechnology
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• v.32 no.2
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• pp.220-227
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• 2022

The spread of antibiotic-resistant strains of Staphylococcus aureus, a gram-positive opportunistic pathogen, has increased due to the frequent use of antibiotics. Inhibition of the quorum-sensing systems of biofilm-producing strains using plant extracts represents an efficient approach for controlling infections. Torilis japonica is a medicinal herb showing various bioactivities; however, no studies have reported the anti-biofilm effects of T. japonica extracts against drug-resistant S. aureus. In this study, we evaluated the inhibitory effects of T. japonica ethanol extract (TJE) on biofilm production in methicillin-sensitive S. aureus (MSSA) KCTC 1927, methicillin-resistant S. aureus (MRSA) KCCM 40510, and MRSA KCCM 40511. Biofilm assays showed that TJE could inhibit biofilm formation in all strains. Furthermore, the hemolysis of sheep blood was found to be reduced when the strains were treated with TJE. The mRNA expression of agrA, sarA, icaA, hla, and RNAIII was evaluated using reverse transcription-polymerase chain reaction to determine the effect of TJE on the regulation of genes encoding quorum sensing-related virulence factors in MSSA and MRSA. The expression of hla reduced in a concentration-dependent manner upon treatment with TJE. Moreover, the expression levels of other genes were significantly reduced compared to those in the control group. In conclusion, TJE can suppress biofilm formation and virulence factor-related gene expression in MSSA and MRSA strains. The extract may therefore be used to develop treatments for infections caused by antibiotic-resistant S. aureus.

• The Plant Pathology Journal
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• v.38 no.5
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• pp.482-489
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• 2022

Fire blight caused by Erwinia amylovora (Ea) is a devastating disease in apple and pear trees. Oxolinic acid (OA), a quinolone family antibiotic that inhibits DNA gyrase, has been employed to control fire blight in South Korea since 2015. The continuous use of this bactericide has resulted in the emergence of OA-resistant strains in bacterial pathogens in other countries. To investigate the occurrence of OA-resistant Ea strains in South Korea, we collected a total of 516 Ea isolates from diseased apple and pear trees in 2020-2021 and assessed their sensitivities to OA. We found that all isolates were susceptible to OA. To explore the possibility of emerging OA-resistant Ea by continuous application of OA, we exposed Ea stains to a range of OA concentrations and constructed OA-resistant mutant strains. Resistance was associated with mutations in the GyrA at codons 81 and 83, which result in glycine to cysteine and serine to arginine amino acid substitutions, respectively. The in vitro growth of the mutants in nutrient media and their virulence in immature apple fruits were lower than those of wild-type. Our results suggest that OA-resistance decreases the fitness of Ea. Future work should clarify the mechanisms by which OA-resistance decreases virulence of this plant pathogen. Continuous monitoring of OA-resistance in Ea is required to maintain the efficacy of this potent bactericide.

• The Korean Journal of Ecology
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• v.27 no.5
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• pp.283-289
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• 2004

This study was conducted to evaluate the annual population variation and identification of antibiotic-resistant bacteria in the lower artificial Lake Geumgang from January to December, 2002. Samples were taken from the surface waters at 3 stations near the estuarine barrage. The results were as follows; the population densities of heterotrophic bacteria varied from 4.1±1.0×10² to 6.7±1.1×10³ cfu ml/sup -1/ during the investigation periods. The population densities of antibiotic-resistant bacteria ranged from 1.5±0.7×10 to 4.3±0.3×10³ cfu ml/sup -1/ for ampicillin; from 0 to 6.4±0.4× 10² cfu ml/sup -1/ for chloramphenicol; from 0 to 2.8±0.3×10³ cfu ml/sup -1/ for gentamicin; from 0 to 4.5±1.0×10³ cfu ml/sup -1/ for kanamycin; and from 1.0±0.4 × 10 to 2.3±0.5×10³ cfu ml/sup -1/ for streptomycin, respectively. Of the sixty isolates, 90% were Gram negative. Dominant genera by 16S rDNA analysis were identified Aeromonas spp. (14 strains), Bacillus spp. (6 strains), Enterobacter spp. (4 strains), and Stenotrophomonas spp. (6 strains). These strains were clustered into 12 groups based on relatedness by average linkage method. Of the 60 isolates, 85% had the resistance to ampicilin and 32% were shown resistance to more than 2 kinds of antibiotics.