• Journal of Microbiology and Biotechnology
• /
• v.31 no.1
• /
• pp.25-32
• /
• 2021

Inflammatory reactions activated by lipopolysaccharide (LPS) of gram-negative bacteria can lead to severe septic shock. With the recent emergence of multidrug-resistant gram-negative bacteria and a lack of efficient ways to treat resulting infections, there is a need to develop novel anti-endotoxin agents. Antimicrobial peptides have been noticed as potential therapeutic molecules for bacterial infection and as candidates for new antibiotic drugs. We previously designed the 9-meric antimicrobial peptide Pro9-3 and it showed high antimicrobial activity against gram-negative bacteria. Here, to further examine its potency as an anti-endotoxin agent, we examined the anti-endotoxin activities of Pro9-3 and elucidated its mechanism of action. We performed a dye-leakage experiment and BODIPY-TR cadaverine and limulus amebocyte lysate assays for Pro9-3 as well as its lysine-substituted analogue and their enantiomers. The results confirmed that Pro9-3 targets the bacterial membrane and the arginine residues play key roles in its antimicrobial activity. Pro9-3 showed excellent LPS-neutralizing activity and LPS-binding properties, which were superior to those of other peptides. Saturation transfer difference-nuclear magnetic resonance experiments to explore the interaction between LPS and Pro9-3 revealed that Trp3 and Tlr7 in Pro9-3 are critical for attracting Pro9-3 to the LPS in the gram-negative bacterial membrane. Moreover, the anti-septic effect of Pro9-3 in vivo was investigated using an LPS-induced endotoxemia mouse model, demonstrating its dual activities: antibacterial activity against gram-negative bacteria and immunosuppressive effect preventing LPS-induced endotoxemia. Collectively, these results confirmed the therapeutic potential of Pro9-3 against infection of gram-negative bacteria.

• Journal of Environmental Science International
• /
• v.16 no.11
• /
• pp.1295-1300
• /
• 2007

The antibacterial effects of anodic electrolyzed water against various bacteria were studied in this investigation. Complete inactivation of Gram-positive and Gram-negative bacteria occurred within 15 s after exposure to anodic electrolyzed water. Moreover, 1/2, 1/5 and 1/10 diluted anodic electrolyzed water by adding deionized water showed strong antibacterial effects. However, the inhibitory effect of anodic electrolyzed water on the anaerobe of Propionibacterium acnes was much weaker than that on the aerobes, including Gram-positive and Gram-negative bacteria. The degraded fragments of E. coli cell were observed upon treating anodic electrolyzed water for 1 min by using scanning electron microscopy.

• Restorative Dentistry and Endodontics
• /
• v.19 no.2
• /
• pp.568-584
• /
• 1994

Bacteria have been regarded as major etiolgic factors in root canal infections. Infected root canal flora from thirteen patients who had visited to conservative department of Wonkwang dental hospital were cultured on blood agar plates. Cultued microorganisms were isolated and identified with Gram stain and biochemical tests using Vitek Systems(BioMeriux, MO, USA); Antibiotic susceptibillity was performed with disk diffusion and broth microdilution using Vitek Systems. Gram positive cocci(65 %) were predominant, which were composed of 6 Streptococcus viridans group, 5 Staph. spp., and 4 Enterococcus faecium, in the isolatd 23 strains. Gram negative rods (26 %) were the next common bacteria, which were composed of 5 non - fermentative Gram negative rods, and 1 Enterobacter cloacae. Most strains of S. viridans group and E. faecium were susceptible to antibiotics including penicillin. But strains of Staphylococcus spp. and non - fermentative Gram negative rods showed marked resistance to antibiotics except tetrancyclin and cefotaxime. Most results between disk diffusion and microdilution were all agreed, but the results of non - fermentative Gram negative rods were susceptible to cefotaxime in disk diffusion method but resistant in microdilution.

• Korean Journal of Veterinary Research
• /
• v.47 no.1
• /
• pp.67-75
• /
• 2007

Environmental mastitis has increased particularly in well-managed or low somatic cell countherds that have successfully controled contagious pathogens. Major pathogens of environmental mastitisare Escherichia coli (E. coli) and Streptococcus uberis. The present study was conducted to investigate1,865 quaters of 241 Korean dairy farms from 2001 to 2004. Prevalence of major gram-negative bacteriaisolated from mastitis milk were E. coli (22.7%) and Enterobacter spp. (16.3%) in coliforms and Pseudomoassp. (10.3%) and Serratia spp. (7.9%) in non-coliforms. The results on antibiotic susceptibility by agardifusion test against these pathogens were 86.7% in piperaciliin, 94.6% in cefepime, 85.5% in amikacin,87.7% in gentamicin and so on. In contrast, the susceptibility against ampicillin (41.9%), cephalothin (9.9%),streptomycin (39.9%) and tetracycline (46.7%) appeared to be below 50%. Gram-negative bacteria showed(96.8%). Acording to year, distribution of high $256{\sim}64{\mu}g/ml$ on cephalothin get increased, but the othersare diferent. These findings demonstrate that major gram-negative bacteria were E. coli and Enterobacterspp. isolates, and often encountered the diverse antibiotic resistant patterns.

• Korean Journal of Food Science and Technology
• /
• v.22 no.1
• /
• pp.26-32
• /
• 1990

Attempts were made to define the characteristics of microbial community as an indicator of Kimchi fermentation. Determination of communities was carried out by simple Gram-stain, followed by direct microcopic counts. In room-temperature $(15^{\circ}C)$ fermentation, microbial succession was occurred in the order of communities of Gram-positive bacteria, yeasts and Gram-negative bacteria. It was characteristic that Gram-positive bacterial community was developed during the production of lactic acid, yeasts community was developed to cause rancidity, and Gram-negative bacterial community was relevant to maceration (or softening) as well as rancidity. The fluctuation of apparent Gram-negative reaction group might be used as a criterion of death or aging of Gram-positive bacterial populations. In low-temperature fermentation $(5^{\circ}C)$, however, it was found that yeasts and Gram-negative bacterial communities did not developed but only Gram-positive bacterial community did. It follows from these results mentioned above that maturity of Kimchi depends on the development of Cram-positive bacterial community. Thus, the size and occurrence of microbial community are avaiable for an indicator of Kimchi fermentation, and also determination of community could be a useful method to predict the maturity.

• Journal of Yeungnam Medical Science
• /
• v.2 no.1
• /
• pp.183-190
• /
• 1985

The glucose nonfermenting gram-negative bacilli encountered about 10% of all gram-negative bacilli isolated from clinical material. Therefore, a rapid and correct identification of glucose nonfermenting gram-negative bacilli is impostent for a better management of infectious disease. There are many conventional systems for the Identification of glucose nonfermenting gram-negative bacilli but most of them have problems and difficulties. Commercial Kit Systems exist and they are too expensive for dally use 10 Korea because of high cost. Based on 12 selected tests we propose a new code system, MCRCODE-N for rapid and 10-expensive identification of glucose nonfermenting gram-negative bacilli. The selective 12 tests are oxidase, glucose oxidation motility, urease, DNase arginine dehydrolase, nitrate reduction, gelatin Liquefaction, esculin hydrolysis, mannitol oxidation, maltose oxidation, Lactose oxidation. The 12 tests are divided 4 group and then each group has 3 tests. The result of each group is expressed by the number as below. The positive test is given by specific number (1st test = 1, 2nd test = 2, 3rd test = 4), while any negative result is 0. Each 3 numbers of one group are added and make number of 1 digit. Four digit number is refered to the code book of MCRCODE-N system or MCRCODE system using computer (Apple-II model) created by authors. This MCRCODE-N system is suitable ones for our use 10 Korea. We propose the MCRCODEN-N system for clinical use.

• Natural Product Sciences
• /
• v.9 no.3
• /
• pp.183-185
• /
• 2003

The combination of hexane extract (E4) of rhizome of Acorus gramineus with chloramphenicol (Cm) was applied to Gram negative Cm resistant microbials to find the possibility of clinical use and to clarify the relationship of the activity of chloramphenicol acetyltransferase (CAT). The combination of $1,000\;{\mu}g/ml$ of E4 and $8\;{\mu}g/ml$ of Cm entirely ceased the growth of S. aureus SA2, a gram positive resistant strain to 10 antibiotics. But in Gram negative strains which possess CAT activity, some showed considerably strong resistances to Cm and some did weakly.

• YAKHAK HOEJI
• /
• v.30 no.2
• /
• pp.79-86
• /
• 1986

In order to study 2-formylpyridine dithiocarbohydrazones (DTCH's) and their Cu(II) chelates as potential effective antimicrobial agents, twelve new compounds of six DTCH's and their Cu(II) chelates were synthesized. The compositions of Cu(II) chelates were determined on the basis of the data obtained from elemental analysis, electronic and IR spectrophotometry, and other method. They were tested for antimicrobial activity in vitro against a gram-positive, seven gram-negative bacterial species and three fungal species. DTCH's exhibited high antibacterial activity against the gram-positive Staphylococcus aureus, but low activity against the various gram negative bacterial species. In contrast to DTCH'S, their Cu(II) chelates exhibited higher antibacterial activity against St. aureus, but weaker, if any, activity against the gram-negative bacterial species. Both DTCH's and their Cu(II) chelates showed relatively potent antifungal activity against Cryptococcus neoformans, but weak activity against Candida albicans and Candida pseudotropicalis.

• 한국생물공학회:학술대회논문집
• /
• 2001.11a
• /
• pp.762-766
• /
• 2001

The nar promoter of Escherichia coli was known to induce maximally under anaerobic or microaerobic conditions in the presence of nitrate. In this study, the nar promoter was tested to see whether the expression level of a reporter gene which fused lacZ gene at nar promoter's downstream, in the some gram negative host strains(Agrobacterium, Pseudomonas and Rhizobium). A nar promoter system(Combination of nar promoter and gram negative strain) was grown under aerobic conditions to absorbance at 600 nm of nearly 2.0 and then, the nar promoter was induced by lowering DO to 1-2% with alternating microaerobic and aerobic condition in the fermentor cultures, using different gram negative hosts. For a wild type nar promoter (pNW61), it was possible to maintain production of ${\beta}-galactosidase$ activity per cell(specific ${\beta}-galactosidase$ activity) at 14,000, 9600, 45 Miller units in the presence of 1% nitrate. and for a nitrate - independent nar promoter (pNW618) at 12,000, 10,400 and 58 Miller units in the absence of nitrate ion, respectively.

• BMB Reports
• /
• v.56 no.6
• /
• pp.326-334
• /
• 2023

Antibiotic resistance (AR) is a silent pandemic that kills millions worldwide. Although the development of new therapeutic agents against antibiotic resistance is in urgent demand, this has presented a great challenge, especially for Gram-negative bacteria that have inherent drug-resistance mediated by impermeable outer membranes and multidrug efflux pumps that actively extrude various drugs from the bacteria. For the last two decades, multidrug efflux pumps, including AcrAB-TolC, the most clinically important efflux pump in Gram-negative bacteria, have drawn great attention as strategic targets for re-sensitizing bacteria to the existing antibiotics. This article aims to provide a concise overview of the AcrAB-TolC operational mechanism, reviewing its architecture and substrate specificity, as well as the recent development of AcrAB-TolC inhibitors.