• Journal of Korean Medicine Rehabilitation
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• v.30 no.1
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• pp.31-45
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• 2020

Objectives In this study, we investigated the antimicrobial activity of a 70% ethanol extract of Maneung-hwan (MEH), which is prescribed by practitioners of oriental medicine for use against methicillin-resistant Staphylococcus aureus (MRSA). Methods The antibacterial activity of MEH against MRSA strains was evaluated using the disc diffusion method, broth microdilution method (minimal inhibitory concentration, MIC), checkerboard dilution test, and time-kill test. The mechanism of action of MEH was investigated by bacteriolysis using detergents or ATPase inhibitors Additionally, mRNA and protein expression were investigated by quantitative reverse transcription-polymerase chain reaction and western blot assay, respectively. Results The MIC of MEH was 25~1,600 ㎍/mL against all the tested bacterial strains. We showed that MEH extract exerts strong antibacterial activity. In the checkerboard dilution test, the fractional inhibitory concentration index of MEH in combination with antibiotics indicated synergism or partial synergism against S. aureus. The time-kill study indicated that the growth of the tested bacteria was considerably inhibited after a 24-h treatment with MEH and selected antibiotics. To measure the cell membrane permeability, MEH (3.9 ㎍/mL) was combined with Triton X-100 (TX) at various concentrations N,N-dicyclohexylcarbodimide (DCCD) was also tested as an ATPase inhibitor. TX and DCCD cooperation against S. aureus exhibited synergistic action. Accordingly, the antimicrobial activity of MEH in the context of cell membrane rupture and ATPase inhibition was assessed. Additionally, the expression of genes and proteins associated with resistance was reduced after exposing MRSA to MEH. Conclusions These results suggest that MEH possesses antibacterial activity and acts as a potential natural antibiotic against MRSA.

• Microbiology and Biotechnology Letters
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• v.48 no.4
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• pp.429-438
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• 2020

The emergence of multi-drug resistant, pathogenic methicillin-resistant Staphylococcus aureus (MRSA) is a threat to global health and has created a need for novel functional therapeutic agents. In this study, we evaluated the underlying mechanisms of the anti-MRSA effect of an azaphilone pigment, sclerotiorin (SCL) from Penicillium sclerotiorum. The antimicrobial activity of SCL was evaluated using agar disc diffusion, broth microdilution, time-kill assays and biophysical studies. SCL exhibits selective activity against Gram positive bacteria including MRSA (range, MIC = 128-1028 ㎍/ml) and exhibited rapid bactericidal action against MRSA with a > 4 log reduction in colony forming units within three hours of administration. Biophysical studies, using fluorescent probes and laser or electron microscopy, demonstrated a SCL dose-dependent alternation in membrane potential (62.6 ± 5.0.4% inhibition) and integrity (> 95 ± 2.3%), and the release of UV260 absorbing materials within 60 min (up to 3.2 fold increase, p < 0.01) of exposure. Further, SCL localized to the cytoplasm and hydrolyzed plasmid DNA. While in vitro checkerboard studies revealed that SCL potentiated the antimicrobial activity of topical antimicrobials such as polymixin, neomycin, and bacitracin (Fractional Inhibitory Concentration Index range, 0.26-0.37). Taken together these results suggest that SCL targets the membrane and DNA of MRSA to facilitate its anti-MRSA antimicrobial effect.

• Microbiology and Biotechnology Letters
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• v.51 no.2
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• pp.212-213
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• 2023

Once known as a major community-genotype, sequence type (ST) 72 methicillin-resistant Staphylococcus aureus (MRSA) strains have been increasingly identified in hospital-associated infections in Korea. Here, we report the complete genome sequence of SA520 isolated from a patient in Korea.

• Journal of Microbiology and Biotechnology
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• v.19 no.12
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• pp.1576-1581
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• 2009

The emergence of methicillin-resistant Staphylococcus aureus (MRSA) has led to an urgent need for the discovery and development of new antibacterial agents. As part of an ongoing investigation into the antibacterial properties of natural products, 20-hydroxyecdysone (20E), isolated from the roots of Achyranthes japonica Nakai, was found to be active against MRSA, either alone or in combination with ampicillin (AM) or gentamicin (GM), via checkerboard assay. This study investigated the antibacterial activity of 20E, which exhibited poor antibacterial activity ($MIC=250-500\;{\mu}g/ml$) against MRSA tested. The combined activity of AM or GE plus 20E against MRSA resulted in fractional inhibitory concentractions (FICs) ranging from 4.00 to $0.031\;{\mu}g/ml$, respectively. Meanwhile, the FIC index ranged from 0.16-4.50, indicating a marked synergistic relationship between AM, GE, and 20E against MRSA. Time-kill assays also showed a remarkable decrease between the combination and the more active compound. Therefore, this study demonstrated that AM, GE, and 20E can act synergistically in inhibiting MRSA in vitro.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.5
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• pp.3315-3322
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• 2015

Staphylococcus aureus is the major causative organism of nasocomial infection being the important pathogen in the clinic. Appearance of staphylococcus aureus resistant to methicillin (MRSA) is becoming a big problem in clinics and dynamics all over the world acquiring antibiotic resistance with virulence factors as its feature differentiated from other pathogenic bacteria fast. This research intended to compare and analyze the correlation of antibiotics resistance between strains with toxin genes and distribution of toxin genes of MRSA 101 strains acquired from clinical specimen in one general hospital (enterotoxin(se), toxic shock syndrome toxin-1(tst), exfoliative toxin(et), Panton Valentine leukocidin(pvl)). seg gene, isolated the most among toxin genes, was detected in 59 strains (58.4%) and more than two toxin genes were detected in 70 strains (69.3%). As a combination possessing toxin genes, it was detected in 19 strains (18.8%) as seb, sec, seg, sei, tst and the second frequent combination was sec, seg, sei shown in 11 strains (10.9%). 19 strains (18.8%) with combinations of toxin genes same with seb, sec, seg, sei, tst had 100% resistance Ampicillin, Benzylpenicillin, Ciprofloxacin, Clindamycin, Gentamicin, Erythromycin, Telithromycin, Tetracycline antibiotics. Strains with many toxin genes showed high correlation of antibiotic resistance. Afterwards, effective therapy and thorough infection management should be preceded not to spread the resistance of MRSA strain.

• Journal of Microbiology and Biotechnology
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• v.19 no.7
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• pp.734-741
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• 2009

Recently, strains of methicillin-resistant Staphylococcus aureus (MRSA) with reduced susceptibility to vancomycin (VCM) have been clinically isolated. The antibacterial activity of a new drug, linezolid (LZD), in such a strain was evaluated by measuring bacterial metabolic activity. A total of 73 MRSA strains having various susceptibilities to VCM were subjected to a novel and highly sensitive chemiluminescence-based assay. LZD MIC in the tested strains, measured by the microbroth dilution method, was within the range 1-4 mg/l (mostly ${\leq}2$mg/l), except for one LZD-resistant strain (NRS127; MIC=7 mg/l), and showed no correlation with VCM resistance. The chemiluminescence assay demonstrated that bacterial metabolic activity was strongly suppressed with increasing LZD concentration. The chemiluminescence intensity curve had a low baseline activity without tailing in most strains. The present results suggest that LZD has strong antibacterial activity against MRSA strains, and would be effective for treatment of infections that are poorly responsive to VCM. The chemiluminescence assay facilitated sensitive and discriminative susceptibility testing within a relatively short time.

• Journal of Korean Academy of Nursing
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• v.37 no.6
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• pp.976-985
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• 2007

Purpose: The aim of this study was to identify the present situation of hospital infection and route of infection by clarifying the transmission aspect of methicillin-resistant Staphylococcus aureus(MRSA) in a Neurosurgical Intensive Care Unit by analysing genotype. Methods: MRSA was cultured from twenty five patients with a tracheostomy, twenty five health care workers, and environments in the Neurosurgical Intensive Care Unit of one hospital in D city. Data was collected from December 21, 2004 to November 5, 2005. MRSA isolates representing each genotype were analyzed by spaA typing and a multiplex PCR method capable of identifying the structural type of the staphylococcal cassette chromosome mec(SCCmec) carried by the bacteria. Results: As the same genotype and gene sequence were found among health care workers, patients, and environments, it was assumed that there was cross transmission among them. Conclusion: This study suggests that first, as the hospital infection by MRSA between health care workers and patients in the Neurosurgical Intensive Care Unit was due to result of cross transmission and the relevance of transmission between them was verified, it is necessary to take preventive measures and conduct education. Secondly, development of nursing interventions and study of infection are needed. Thirdly, consistent investment in prevention against hospital infections and environmental renovation is needed.

• Journal of Microbiology and Biotechnology
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• v.15 no.5
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• pp.1039-1046
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• 2005

The salt resistance of antibacterial activity and synergistic effect with clinically used antibiotic agents are critical factors in developing effective peptide antibiotic drugs. For this reason, we investigated the resistance of antibacterial activity to antagonism induced by NaCl and $MgCl_2$ and the synergistic effect of P20 with cefotaxime. P20 is a 20-residue synthetic peptide derived from a cecropin A (CA)-melittin(ME) hybrid peptide. In this study, P20 was found to have potent antibacterial activity against clinically isolated methicillin-resistant Staphylococcus aureus (MRSA) strains without hemolytic activity against human erythrocytes. The combination study revealed that P20 in combination with cefotaxime showed synergistic antibacterial activity in an energy-dependent manner. We also confirmed the synergism between P20 and cefotaxime by fluorescence-activated flow cytometric analysis by staining bacterial cells with propidium iodide (PI) and bis-(1,3-dibutylbarbituric acid) trimethine oxonol (BOX). This study suggests that P20 may be useful as a therapeutic antibiotic peptide with synergistic effect in combination with conventional antibiotic agents.

• Korean Journal of Veterinary Research
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• v.39 no.2
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• pp.383-389
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• 1999

A randomized experimental study was done to evaluate short course therapeutic efficacies of two types of mupirocin ointment (Bactroban Nasal and Bactroban) in the elimination of methicillin-resistant Staphylococcus aureus (MRSA) nasal colonization (16 dogs) and wound infection (3 dogs or 18 wound sites) in dogs. In each model, dogs being assigned to TR-1 treatment group was given ointment twice a day for two consecutive days, and those that assigned to TR-2 treatment group was given the same dose for three days. Neither TR-1 nor TR-2 regimen was effective to clear nasal carriage completely with a clearing rate of 62.5% and 87.5%, respectively. Whereas, for 2 days at least twice daily application of mupirocin for wound infection was quite enough to eliminate MRSA, with a clearing rate of 83.3~100% by 4 weeks follow-up. No apparent side effects were observed in each model, and in no case was it necessary to discontinue the treatment. Further controlled studies on the elimination of nasal colonization are required to establish cost-effective and efficient regimen on companion animals.

• Journal of Life Science
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• v.20 no.4
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• pp.589-596
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• 2010

We investigated antimicrobial activities of various pine (Pinus densiflora) needle extracts against antibiotic resistant strains of Staphylococcus aureus. Hot water extract showed the highest antimicrobial activity against normal and methicillin resistant Staphylococcus aureus (MRSA), however, it exhibited no antimicrobial activity against penicillin resistant S. aureus (PRSA). Hot water-hexane (HWH), hot water-ethanol (HWE), hexane, and ethanol extracts showed antimicrobial activity against S. aureus, PRSA and MRSA. Minimum inhibitory concentrations (MIC) of HWH, HWE, hexane, and ethanol extracts were 0.05, 0.05, 0.5 and 5 mg/ml, respectively, and HWH and HWE extracts showed the strongest antimicrobial activity among these extracts. Antimicrobial activities of pine needle extracts were stable after heating at $121^{\circ}C$ for 20 min. These results suggested that pine needle extracts can be used as an effective natural antimicrobial agent for food and medical industries.