• Journal of Microbiology and Biotechnology
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• v.20 no.12
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• pp.1672-1676
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• 2010

The Actinomycete strain KH29 is antagonistic to the multidrug-resistant Acinetobacter baumannii. Based on the diaminopimelic acid (DAP) type, and the morphological and physiological characteristics observed through the use of scanning electron microscopy (SEM), KH29 was confirmed as belonging to the genus Streptomyces. By way of its noted 16S rDNA nucleotide sequences, KH29 was found to have a relationship with Streptomyces cinnamonensis. The production of an antibiotic from this strain was found to be most favorable when cultured with glucose, polypeptone, and yeast extract (PY) medium for 6 days at $27^{\circ}C$. The antibiotic produced was identified, through comparisons with reported spectral data including MS and NMR as a cyclo(L-tryptophanyl-L-tryptophanyl). Cyclo(L-Trp-L-Trp), from the PY cultures of KH29, was seen to be highly effective against 41 of 49 multidrug-resistant Acinetobacter baumannii. Furthermore, cyclo(L-Trp-L-Trp) had antimicrobial activity against Bacillus subtilis, Micrococcus luteus, Staphylococcus aureus, Saccharomyces cerevisiae, Aspergillus niger, and Candida albicans, However, it was ineffective against Streptomyces murinus.

• Journal of Microbiology and Biotechnology
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• v.9 no.5
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• pp.613-618
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• 1999

L-Proline-producing mutant strains were developed by exposing L-glutamic acid-producing bacteria to N-metyl-N-nitro-nitrosoguanidine and UV irradiation. A L-histidine auxotroph of Corynebacterium acetoacidophilum RYU3161(KCTC 0616BP), which was resistant to sulfaguanidine and proline analogs (DHP, AZC, TAC), was isolated. The activity of the mutant strain's $\gamma$-glutamyl kinase was 45% higher than that of the parent strain. The optimum level of L-histidine for production of L-proline was 0.16 g/l. In a 5-1 jar fermenter, the mutant strain produced L-proline at a high concentration (35 g/l) level within 48 h of cultivation.

• Microbiology and Biotechnology Letters
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• v.40 no.3
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• pp.197-207
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• 2012

This study investigated the role of plasmids and their relationship with the multiple antibiotic resistance of 30 Vibrios sp. isolated from molluscs and crustaceans sampled from the Kerala coastal waters of India. The biochemical identification and antibiotic resistance profiles were determined, followed by the plasmid profiles, conjugation and transformation efficiencies. The results showed a considerable difference in the level of bacterial resistance to various antibiotics; while all 30 strains were found to be MAR Vibrios sp. and their resistance patterns varied. All the strains were resistant to amoxycillin, ampicillin and carbeniciliin. 87% were resistant to rifampicin; 74% to cefuroxime; 67 to streptomycin; 53% to norfloxacin and ciprofloxacin and 47% to furazolidone and nalidixic acid. In addition to their antibiotic resistance, the plasmid DNA of the MAR Vibrios strains isolated from the molluscs and crustaceans was also studied. Nine strains isolated from crustaceans and molluscs were found to harbor 1-3 plasmids with sizes varying from 5. 98 kb to 19. 36 kb. The average transformation efficiency was about $5{\times}10^{-8}$ and the conjugation efficiency varied from $2.1{\times}10^{-3}$ to $10^{-9}$. A further study of antibiotic resistance patterns may be useful to test the extent of drug resistance in seafoods and help to devise a nationwide antibiotic policy.

• Korean Journal of Veterinary Service
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• v.32 no.1
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• pp.93-102
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• 2009

In this study, antimicrobial resistance of E. coli isolated from domestic beef on sale in Busan and Gyeongnam province was investigated from March to October 2008. A total of 400 beef samples were collected for the monitoring of antimicrobial resistance, and 39 (9.8%) strains of E. coli were isolated. Antimicrobial resistance test was carried out by agar disc diffusion method with 17 antimicrobials. In general, E. coli isolates showed the highest antimicrobial resistance to tetracycline (85.3%), followed by doxycycline (76.5%), streptomycin (61.8%) and sulfamethoxazole/trimethoprim (61.8%). Then they showed higher resistance to several antimicrobials like kanamycin and neomycin (55.9%). However, They had low antimicrobial resistance to amikacin (8.8%), amoxicillin/clavulanic acid (2.9%). Of 39 isolates, 31 (79.5%) were resistant to more than 2 antimicrobials. Among 17 antimicrobials examined, tetracyclines were the most resistant, followed by aminoglycosides, sulfonamides. The resistance was seemed to be correlated to amounts of antimicrobial use. In the result of this study, we suggest that there be need to regulate the abuse of antimicrobial on food-producing animals in Korea because the concern on antimicrobial resistant is gradually increased worldwide.

• Journal of Microbiology and Biotechnology
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• v.32 no.10
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• pp.1284-1291
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• 2022

The rise of methicillin-resistant Staphylococcus aureus (MRSA) has resulted in significant morbidity and mortality, and clinical treatment of MRSA infections has become extremely difficult. Sortase A (SrtA), a virulence determinant that anchors numerous virulence-related proteins to the cell wall, is a prime druggable target against S. aureus infection due to its crucial role in the pathogenicity of S. aureus. Here, we demonstrate that isovitexin, an active ingredient derived from a variety of traditional Chinese medicines, can reversibly inhibit SrtA activity in vitrowith a low dose (IC₅₀=24.72 ㎍/ml). Fluorescence quenching and molecular simulations proved the interaction between isovitexin and SrtA. Subsequent point mutation experiments further confirmed that the critical amino acid positions for SrtA binding to isovitexin were Ala-92, Ile-182, and Trp-197. In addition, isovitexin treatment dramatically reduced S. aureus invasion of A549 cells. This study shows that treatment with isovitexin could alleviate pathological injury and prolong the life span of mice in an S. aureus pneumonia model. According to our research, isovitexin represents a promising lead molecule for the creation of anti-S. aureus medicines or adjuncts.

• Journal of Pharmacopuncture
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• v.25 no.1
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• pp.37-45
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• 2022

Objectives: The quorum-sensing-inhibitory and anti-biofilm activities of the methanol extract of E. globulus leaves were determined against clinically isolated multidrug-resistant Pseudomonas aeruginosa. Methods: The preliminary anti-quorum-sensing (AQS) activity of eucalyptus was investigated against a biosensor strain Chromobacterium violaceum ATCC 12472 (CV12472) by using the agar well diffusion method. The effect of sub-minimum inhibitory concentrations (sub-MICs) of the methanol extract of eucalyptus on different quorum-sensing-regulated virulence factors, such as swarming motility, pyocyanin pigment, exopolysaccharide (EPS), and biofilm formation, against clinical isolates (CIs 2, 3, and 4) and reference PA01 of Pseudomonas aeruginosa were determined using the swarm diameter (mm)-measurement method, chloroform extraction method, phenol (5%)-sulphuric acid (concentrated) method, and the microtiter plate assay respectively, and the inhibition (%) in formation were calculated. Results: The preliminary AQS activity (violacein pigment inhibition) of eucalyptus was confirmed against Chromobacterium violaceum ATCC 12472 (CV12472). The eucalyptus extract also showed concentration-dependent inhibition (%) of swarming motility, pyocyanin pigment, EPS, and biofilm formation in different CIs and PA01 of P. aeruginosa. Conclusion: Our results revealed the effectiveness of the E. globulus extract for the regulation of quorum-sensing-dependent virulence factors and biofilm formation at a reduced dose (sub-MICs) and suggest that E. globulus may be a therapeutic agent for curing and controlling bacterial infection and thereby reducing the possibility of resistance development in pathogenic strains.

• Journal of Microbiology and Biotechnology
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• v.33 no.5
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• pp.698-705
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• 2023

Rapid diagnosis of methicillin-resistant Staphylococcus aureus (MRSA) is essential for guiding clinical treatment and preventing the spread of MRSA infections. Herein, we present a simple and rapid MRSA screening test based on the aggregation effect of mannose-binding lectin (MBL)-conjugated gold nanoparticles (AuNP), called the MRSA probe. Recombinant MBL protein is a member of the lectin family and part of the innate immune system. It can recognize wall teichoic acid (WTA) on the membrane of MRSA more specifically than that of methicillin-sensitive Staphylococcus aureus (MSSA) under optimized salt conditions. Thus, the MRSA probe can selectively bind to MRSA, and the aggregation of the probes on the surface of the target bacteria can be detected and analyzed by the naked eye within 5 min. To demonstrate the suitability of the method for real-world application, we tested 40 clinical S. aureus isolates (including 20 MRSA specimens) and recorded a sensitivity of 100%. In conclusion, the MRSA probe-based screening test with its excellent sensitivity has the potential for successful application in the microbiology laboratory.

• Journal of Microbiology and Biotechnology
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• v.8 no.5
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• pp.547-551
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• 1998

Sixty isolates of lactic acid bacteria found in kimchi, a traditional Korean dish of fermented vegetables, were tested for nisin sensitivity. Of the sixty isolates, all belonging to the genera Leuconostoc, Lactobacillus, and Pediococcus, fifty isolates were sensitive to nisin at a concentration of 100 IU/$m\ell$, and four isolates appeared to be resistant to nisin. This demonstrated that the nisin sensitivity of lactic acid bacteria found in kimchi varied considerably among isolates. In MRS broth containing nisin at concentrations of 100 to 300 IV/$m\ell$, the growth of sensitive isolates of Leuconostoc mesenteroides and Lactobacillus plantarum was inhibited for two to three days at 2$0^{\circ}C$. When nisin was added to kimchi preparations at a concentration of 100 IU/$m\ell$, the growth of lactic acid bacteria was delayed and reached a maximum two days later than that in kimchi without nisin. These results suggest the possible use of nisin in kimchi preparation, at recommended levels, to control the lactic acid fermentation. Scanning electron micrographs of a sensitive isolate L. plantarum revealed the formation of pores on cell surfaces followed by rapid cell wall destruction 1 h after the addition of nisin.

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.44 no.6
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• pp.15-20
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• 2012

The effects of sulfur dioxide on paper were investigated since these sulfur compounds could cause damages on cellulose and organic materials in papers. For the reason, exposure ageing tests were performed on traditional Korean paper (Hanji) and two different types of modern paper (acid-free and acid paper) to determine the damage with regard to the optical as well as physicochemical properties according to the varying $SO_2$ concentration. As a result, optical properties were not changed while physical and chemical peoperties were remarkably changed with the exposure period. In the case of pH, $SO_2$ had little impact on the pH of the Hanji and acid-free paper while the pH of acid paper was remarkably decreased. The decrease of the folding endurance of the Hanji was relatively smaller than those of the acid-free and acid paper. The results prove Hanji was more resistant to $SO_2$ than the modern paper in terms of optical, physical and chemical properties. In addition, it was also suggested that $SO_2$ concentration should be kept below 0.01 ppm for the preservation of paper objects.

• Proceedings of the KOR-BRONCHOESO Conference
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• 1981.05a
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• pp.39.2-39
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• 1981

Recently, there has been many problems in the treatment of OMPC, because of inadequate and abuse of antibiotics, and resistant strain of pathogenic organisms to antibiotics. Authors studied on the culture and sensitivity of otorrhea obtained from 50 patients with OMPC, and evaluated the therapeutic effect of PPA, which is a new derivative of piromidic acid and active against gram (-) bacteria including pseudomonas aeruginosa as well as some gram (+) bacteria. We observed good therapeutic effect on OMPC with pseudomonas and other gram (-) bacteria, and considerable effect on OMPC with gram (+) bacteria.