• Journal of Food Hygiene and Safety
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• v.35 no.2
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• pp.103-108
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• 2020

Recently, consumer demand for safe but minimally processed food has rapidly increased. For this reason, many food processing industries are applying hurdle technology to enhance food safety, extend shelf life, and make foods appear minimally processed. Meanwhile, studies have shown that a treatment (stress) meant to inactivate foodborne pathogens may trigger adaptation mechanisms and could even offer cross protection against subsequent treatments. Also, certain routine farm practices such as antibiotic and herbicide use could result in the development of antibiotic-resistant pathogens. Such bacteria may be tolerant to food processing-associated stress and be more likely to remain viable in processed foods. In this review, we discuss the correlation between food processing-associated stress and antibiotic resistance. We also discuss molecular mechanisms such as the use of sigma factors, SOS response pathways and efflux pumps as means of cross protection against antimicrobial compounds and other food processing-associated stresses.

• Environmental Engineering Research
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• v.25 no.4
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• pp.614-621
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• 2020

Antibiotic pollution is one of the factors contributing to the spread of antibiotic-resistant bacteria in the environment. Advanced oxidation and irradiation processes have been introduced to eliminate antibiotics from water and wastewater. However, few studies have reported the toxic effects of residual antibiotics and their byproducts induced by a treatment system. In this study, we compared the efficacies of chemical (high-performance liquid chromatography (HPLC)) and biological (antimicrobial susceptibility test) assays for measuring the concentrations of residual antibiotics after gamma irradiation for degrading amoxicillin, cephradine, lincomycin, and tetracycline. The concentrations of residual antibiotics estimated using the two assay methods were almost identical, except cephradine. In the case of cephradine, inhibited bacterial growth was observed that was equivalent to twice the concentration measured by HPLC in the samples subjected to gamma irradiation. The observed inhibition of bacterial growth suggested the generation of potentially toxic intermediates following antibiotic degradation. These results indicate that biological and chemical assays should be used in concert for monitoring antibiotic contamination and the toxic derivatives of antibiotic degradation. The results demonstrate that these four antibiotics can be decomposed by 2.0 kGy gamma-irradiation without toxic effects of their byproducts.

• Korean Journal of Veterinary Research
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• v.20 no.2
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• pp.85-92
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• 1980

The antimicrobial drug susceptibility of 439 isolates of animal pathogens recovered from various clinical cases during 1978-79 has been investigated by the use of disk diffusion technique. The majority of 308 strains of Eschericihia coli were highly resistant to bacitracin, erythromycin, penicillin, streptomycin and tetracyclinon while only 0.3 per cent of them were resistant to gentamicin and 3.2 per cent to colistin. The percentages of strains resistant to ampicillin, carbenicillin, cephalothin, chloramphenicol and neomycin were 30.5%, 24.7%, 11:4%, 28.2% and 26.2% and repectively. However, none of E. coli cultures of ovine origin were resistant to ampicillin, carbenicillin, chloramphenicol, colistin, gentamicin, kanamycin, and neomycin. A total of 39 patterns of multipe drug1 resistance of 308 strains E. coli against 9 drugs in general use such as ampicillin, cephalothin, chloramphenicol, colistin, gentamicin, kanamycin, neomycin, streptomycin and tetracycline were observed and the most common multiple resistance patterns were SM, TC pattern (20.5%) and AM, CP, KM, NM, SM, TC pattern (9.7%). None of the 43 cultures of salmonella organism from pigs and chickens were resistant to ampicillin, carbenicillin, cephalothin, colistin, gentamicin and kanamycin; and the majority of the cultures were susceptible to chloramphenicol (90.0%), neomycin (97.7%) and tetracycline (93.0%). All the cultures were found to be resistant to bacitracin and penicillin and the rate of resistant strains to erythromycin and s treptomycin being 79.1% and 41.9% respectively. It was found that the majority of 63 cultures of staphylococcal isolates were resistant to lincomycin, penicillin, streptomycin and tetracycline. The percentages of 63 staphylococcal isolates susceptible to gentamicin, nitrofurantoin, cephalothin, ampicillin, methicillin, bacitracin and chloramphenicol were 98.4%, 98.4%, 95.2%, 93.7%, 93.7%, 92.1% and 92.1% respectively. The 25 cultures of streptococcal isolates were resistant in order of prevalence to streptomycin(88.0%), kanamycin(68.0%), gentamicin (44.0%), tetracycline (44.0%) and methicillin (40.0%) wihle the majority of them were sensitive to ampicillin, bacitracin, chloramphenicol and penicillin.

• Journal of fish pathology
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• v.23 no.1
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• pp.37-45
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• 2010

In this study, we carried out research on the level of single and multi-drug resistance of bacteria isolated from cultured flounder Paralichthys olivaceus. One hundred sixty one bacteria were isolated from cultured olive flounder Paralichthys olivaceus in Korea and the isolates consisted of Edwardsiella tarda (n=32), Vibrio ichthyoenteri (n=37), Vibrio spp. (n=54), Streptococcus parauberis (n=28) and Streptococcus spp. (n=10). These E. tarda isolates were highly resistant in the order of tetracycline (84.4%) and oxolinic acid (71.9%). V. ichthyoenteri and Vibrio spp. showed resistance ampicillin (94.6% and 81.5%) and tetracycline (56.8% and 42.6%). S. parauberis isolates were resistant ampicillin (57.1%), tetracycline (57.1%) and erythromycin (35.7%). Of the isolates, 84.4% of E. tarda, 73.0% of V. ichthyoenteri, 57.4% of Vibrio spp., 42.8% of S. parauberis and 70.0% of Streptococcus spp. isolates exhibited multi-drug resistance against more than two antibiotics.

• The Korea Journal of Herbology
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• v.30 no.5
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• pp.15-21
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• 2015

Objectives : Methicillin-resistantStaphylococcus aureus(MRSA) is a human pathogen. New antibacterial agents are needed to treat MRSA-related infections. This study investigated the antibacterial activity of EtOH 70% extracts ofTonghyeonipal-dan(THD) which prescription is composed of oriental medicine against MRSA.Methods : The antibacterial activity of THD was evaluated against MRSA strains by using the Disc diffusion method, broth microdilution method, Checkerboard dilution test, and Time-kill test; its mechanism of action was investigated by bacteriolysis, detergent or ATPase inhibitors were used.Results : The minimum inhibitory concentration (MIC) of THD is 1,000~2,000 μg/mL against MRSA. In the checkerboard dilution test, fractional inhibitory concentration index (FICI) of THD in combination with antibiotics indicated synergy or partial synergism againstS. aureus. Furthermore, a time-kill assay showed that the growth of the tasted bacteria was considerably inhibited after 24 h of treatment with the combination of THD with selected antibiotics. For measurement of cell membrane permeability, THD 500 μg/mL along with concentration of Triton X-100 (TX) and Tris-(hydroxymethyl) aminomethane (TRIS) were used. In the other hand, N,N-dicyclohexylcarbodimide (DCCD) and Sodium azide (NaN3) were used as an inhibitor of ATPase. TX, TRIS, DCCD and NaN3 cooperation againstS. aureusshowed synergistic action.Conclusions : Accordingly, antimicrobial activity of THD was affected by cell membrane and inhibitor of ATPase were assessed. These results suggest that THD has antibacterial activity, and that THD extract offers great potential as a natural antibiotic against MRSA.

• Annals of Laboratory Medicine
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• v.38 no.6
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• pp.545-554
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• 2018

Background: The increasing morbidity and mortality rates associated with Acinetobacter baumannii are due to the emergence of drug resistance and the limited treatment options. We compared characteristics of colistin-resistant Acinetobacter baumannii (CR-AB) clinical isolates recovered from patients with and without prior colistin treatment. We assessed whether prior colistin treatment affects the resistance mechanism of CR-AB isolates, mortality rates, and clinical characteristics. Additionally, a proper method for identifying CR-AB was determined. Methods: We collected 36 non-duplicate CR-AB clinical isolates resistant to colistin. Antimicrobial susceptibility testing, Sanger sequencing analysis, molecular typing, lipid A structure analysis, and in vitro synergy testing were performed. Eleven colistin-susceptible AB isolates were used as controls. Results: Despite no differences in clinical characteristics between patients with and without prior colistin treatment, resistance-causing genetic mutations were more frequent in isolates from colistin-treated patients. Distinct mutations were overlooked via the Sanger sequencing method, perhaps because of a masking effect by the colistin-susceptible AB subpopulation of CR-AB isolates lacking genetic mutations. However, modified lipid A analysis revealed colistin resistance peaks, despite the population heterogeneity, and peak levels were significantly different between the groups. Conclusions: Although prior colistin use did not induce clinical or susceptibility differences, we demonstrated that identification of CR-AB by sequencing is insufficient. We propose that population heterogeneity has a masking effect, especially in colistin non-treated patients; therefore, accurate testing methods reflecting physiological alterations of the bacteria, such as phosphoethanolamine-modified lipid A identification by matrix-assisted laser desorption ionization-time of flight, should be employed.

• Journal of the Korean Society of Food Science and Nutrition
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• v.34 no.6
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• pp.910-914
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• 2005

This study was to determine the inhibitory effect of ethanol extract of leaf, bark and xylem of Quercus aliena Blume and, consecutively, of organic solvent subfractions against food borne pathogens. The ethanol extracts of leaf, bark and xylem of Quercus aliena Blume were shown to have antimicrobial effect against Gram-positive and Gram-negative bacteria. Listeria monocytogenes and Salmonella Typhimurium were more resistant to ethanol extracts of the Quercus aliena Blume tissues compared with Bacillus cereus and Escherichia coli O157:H7. The ethanol extract of Quercus aliena Blume leaf showed the strongest antimicrobial activity against food borne pathogens, followed by those of xylem and bark. The ethanol extract treatment $(500\~1,000\mu g/mL)$ of Quercus aliena Blume leaf completely reduced the growth of B. cereus and L. monocytogenes within 24 hour whereas $2,000\mu g/mL$ of ethanol extract was needed for complete growth inhibition of E. coli O157:H7 and S. Typhimurium. Among organic solvent subfractions obtained from the ethanol extract of leaf, bark and xylem of Quercus aliena Blume, the ethyl acetate fraction showed the strongest antimicrobial activity, but no antimicrobial activity was observed in chloroform, hexane and water fractions.

• Korean Journal of Organic Agriculture
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• v.22 no.3
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• pp.469-481
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• 2014

IIn vitro antimicrobial and anti-inflammatory activities of nargenicin and its derivatives were investigated. Nargenicin, an unusual macrolide antibiotic with potent anti-MRSA (methicilin-resistant Staphylococcus aureus) activity, was purified from the culture broth of Nocardia sp. CS682. And variety of novel nargenicin derivatives was synthesized from nargenicin. Two compounds (4 and 5) exhibit a broad spectrum of antimicrobial activities against infectious bacteria. The antimicrobial activity of derivatives against fifteen organisms was assessed using the minimum inhibitory concentration (MIC). The MIC values were in the ranges of $0.15{\sim}80{\mu}g/mL$ (w/v) for compound 1 and 2, $5{\sim}80{\mu}g/mL$ (w/v) for compound 3, $1.25{\sim}40{\mu}g/mL$ (w/v) for compound 4, and $1.25{\sim}80{\mu}g/mL$ (w/v) for compound 5, depending on the pathogens studied. In vitro, we investigated cytotoxicity and inhibition of nitric oxide (NO) production of synthesized compounds 1-5 in Raw 264.7 cells. LPS-induced nitric oxide releases were significantly blocked by compound 3, 4 and 5 in a dose-dependent manner. At high concentrations ($5{\mu}g/mL$) compound 5 inhibited the NO production by 95%. Compound 4 inhibited the release of NO in LPS-activated Raw 264.7 cells by 75% at the concentration of $10{\mu}g/mL$. Compound 3 inhibited the release of NO in LPS-activated Raw 264.7 cells by 65% at the concentration of $100{\mu}g/mL$. On the other hand, nargenicin, compound 1 and 2 did not inhibit NO production. These results demonstrated that compound 4 and 5 displayed antimicrobial activity and blocked LPS-induced pro-inflammatory mediators such as NO in macrophages, which might be responsible for its therapeutic application.

• Journal of Life Science
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• v.33 no.12
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• pp.1015-1024
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• 2023

Antibiotics have greatly contributed to the treatment and prevention of bacterial diseases in humans, animals, and fish. However, antibiotic misuse has led to the emergence and spread of multidrug-resistant bacteria. In addition to antibiotic discovery research, efforts are being made to combat such multidrug-resistant bacteria using antimicrobial agents, antioxidants, host immune enhancement, probiotics, and bacteriophages, as well as various symptomatic therapies. To discover novel bioactive compounds, it is crucial to adopt approaches that incorporate fresh ideas, new targets, innovative techniques, and untapped resources. Halophytes are plants that grow in high-salt soils and are known to adapt to salt-induced stress through unique metabolic processes that produce secondary metabolites. This study aimed to investigate the effects of extracts of halophytes native to Korea on oxidative stress and to determine whether they exert inhibitory activity against biofilms, which are major pathogenic factors of infectious bacteria. The Acinetobacter baumannii strain ATCC 17978, a representative drug-resistant bacterium, was used to measure anti-biofilm activity. The results showed that Aster spathulifolius, Carex kobomugi, Rosa rugosa, and Asparagus cochinchiensis exerted strong antioxidant and anti-biofilm effects without affecting bacterial growth itself. The halophytes used in this study are promising candidates for the development of pharmaceutical agents with antioxidant and antimicrobial properties.

• Mass Spectrometry Letters
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• v.5 no.4
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• pp.110-114
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• 2014

The method of direct mass spectrometry profiling is reliable and reproducible for the rapid identification of clinical isolates of bacteria and fungi. This is the first study evaluating the approach of MALDI-TOF mass spectrometry profiling for rapid identification of carbapenemase-resistant enterobacteriaceae (CRE). Proof of concept was achieved by the discrimination of CRE using MALDI Biotyper MS based on the protein. This profiling appears promising by the visual observation of consistent unique peaks, albeit low intensity, that could be picked up from the mean spectra (MSP) method. The Biotyper MSP creation and identification methods needed to be optimized to provide significantly improved differences in scores to allow for subspecies identification with and without carbapenemases. These spectra were subjected to visual peak picking and in all cases; there were pertinent differences in the presence or absence of potential biomarker peaks to differentiate isolates. We also evaluated this method for potential discrimination between different carbapenemases bacteria, utilizing the same strategy. Based on our data and pending further investigation in other CREs, MALDI-TOF MS has potential as a diagnostic tool for the rapid identification of even closely related carbapenemases but would require a paradigm shift in which Biotyper suppliers enable more flexible software control of mass spectral profiling methods.