• Journal of Microbiology and Biotechnology
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• v.33 no.4
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• pp.500-510
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• 2023

In this study, lactic acid bacteria were isolated from 21 top-selling probiotic products on Korean market and their antimicrobial resistance were analyzed. A total 152 strains were claimed to be contained in these products and 70 isolates belonging to three genera (Bifidobacterium, Lactobacillus, and Lactococcus) were obtained from these products. RAPD-PCR showed diversity among isolates of the same species except for two isolates of Lacticaibacillus rhamnosus from two different products. The agar dilution method and the broth dilution method produced different MICs for several antimicrobials. With the agar dilution method, five isolates (three isolates of Bifidobacterium animalis subsp. lactis, one isolate of B. breve, one isolate of B. longum) were susceptible to all nine antimicrobials and 15 isolates were multi-drug resistant. With the broth microdilution method, only two isolates (one isolate of B. breve and one isolate of B. longum) were susceptible while 16 isolates were multi-drug resistant. In this study, only two AMR genes were detected: 1) lnu(A) in one isolate of clindamycin-susceptible and lincomycin-resistant Limosilactobacillus reuteri; and 2) tet(W) in one tetracycline-susceptible isolate of B. longum B1-1 and two tetracycline-susceptible isolates and three tetracycline resistant isolates of B. animalis subsp. lactis. Transfer of these two genes via conjugation with a filter mating technique was not observed. These results suggest a need to monitor antimicrobial resistance in newly registered probiotics as well as probiotics with a long history of use.

• Journal of Microbiology and Biotechnology
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• v.26 no.12
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• pp.2043-2050
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• 2016

Exploring novel antibiotics is necessary for multidrug-resistant pathogenic bacteria. Because the probiotics in soybean food have antimicrobial activities, we investigated their effects on multidrug-resistant Acinetobacter baumannii. Nineteen multidrug-resistant A. baumannii strains were clinically isolated as an experimental group and 11 multidrug-sensitive strains as controls. The growth rates of all bacteria were determined by using the analysis for xCELLigence Real-Time Cell. The combination of antibiotics showed synergistic effects on the strains in the control group but no effect on the strains in the experimental group. Efflux pump gene adeS was absent in all the strains from the control group, whereas it exists in all the strains from the experimental group. Furthermore, all the strains lost multidrug resistance when an adeS inhibitor was used. One strain of probiotics isolated from soybean food showed high antimicrobial activity for multidrug-resistant A. baumannii. The isolated strain belongs to Bacillus subtilis according to 16S RNA analysis. Furthermore, E. coli showed multidrug resistance when it was transformed with the adeS gene from A. baumannii whereas the resistant bacteria could be inhibited completely by isolated Bacillus subtilis. Thus, probiotics from soybean food provide potential antibiotics against multidrug-resistant pathogenic bacteria.

• 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.

• Biomolecules & Therapeutics
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• v.13 no.4
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• pp.240-245
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• 2005

An antimicrobial molecule was purified from centipede, Scolopendra subspinipes mutilans L. Koch, by reverse phase-HPLC. Its molecular weight was determined to be 1208.5493 by using matrix-assisted laser desorption ionization-time of flight (MALDI-TOF) mass spectrometry. Total amino acid composition analysis revealed that it consists of E, G, P, V, L, F, and W. It exhibited a broad antimicrobial spectrum against not only Gram-negative, but also Gram-positive bacteria. Furthermore, it was found to have an antimicrobial activity against vancomycin resistant enterococci (VRE). It may be a useful molecule for a new antibiotic development, especially against drug-resistant bacteria. We suggest that it may playa role in the defense system of this animal. This is the first report of a peptidic antimicrobial substance from centipede.

• Korean Journal of Pharmacognosy
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• v.34 no.2 s.133
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• pp.142-144
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• 2003

Acetone extracts of 301 strains of marine-derived fungus were tested for antimicrobial activity against three strains of bacteria. The bacteria consisted of three pathogens, Staphylococcus aureus, methicillin-resistant S. Aureus, and multidrug-resistant S. aureus. The acetone extracts of 10 strains (MFA117, MFA130, MFA134, MFA206, MFA217, MFA268, MFA277, MFA291, MFA292, MFA301) showed strong activity, inhibiting 100% of the bacterial growth. These antimicrobial active strains were cultlued in SWS medium on a 1 L scale and the resulting broth and mycelium were extracted to afford mycelium extract (000M) and broth extract (000B), respectively. Antimicrobial activity for all extracts has been tested as the results, the mycelium extract of one strain (217M) and the broth extracts of 9 strains (117B,130B, 134B, 206B, 268B, 277B, 291B, 292B, 301B) exhibited relatively high levels of activity at minimal inhibitory concentration (MIC) values of $500-125\;{\mu}g/mL$ range. Among them, the extracts, 277B, 291B, 292B and 301B showed the most significant antimicrobial activity with $IC_{50}$ values of $125\;{\mu}g/mL$.

• Journal of the Korean Magnetic Resonance Society
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• v.6 no.1
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• pp.69-77
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• 2002

During the screening of material which has the antimicrobial activity against aminoglycoside-resistant bacteria, A new material $\varepsilon$-(L-$\beta$-Iysine) polypeptide from a culture medium of Streptomyces sp.(DWGS2) was isolated, and the structure and the physicochemical properties of the new material were elucidated. The new material was separated by column chromatography of the culture medium using Dowex1$\times$2, Silica gel, and Sephadex LH20 etc. The chemical structure and molecular weight were determined with the data of various NMR experiments, MALDI mass, and ESI mass experiments. The antimicrobial activity of $\varepsilon$-(L-$\beta$-Iysine) polypeptide is not only better than equal to the activity of known aminoglycoside type of antibiotics(MIC=3.125 - 6.25ug/mL) but also effective against aminoglycoside-resistant bacteria and fungi. If the mechanism of antimicrobial activity against aminoglycoside- resistant bacteria is figured out, the $\varepsilon$-(L-$\beta$-Iysine) polypeptide can be utilized for the treatment of diseases caused by aminoglycoside-resistant bacteria.

• 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.

• Microbiology and Biotechnology Letters
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• v.42 no.2
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• pp.152-161
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• 2014

The in vitro antimicrobial potential of the unexplored Moringa oleifera seed coat (SC) was evaluated against some Gram-positive and Gram-negative bacteria and yeast pathogens. Antimicrobial studies with various solvent extracts indicated ethyl acetate to be the best extractant, which was used for the rest of the antimicrobial studies as it tested neither toxic nor mutagenic. Gram-positive bacteria including a methicillin resistant Staphylococcus aureus (MRSA) strain were more susceptible with a minimum inhibitory concentration (MIC) range of 0.03-0.04 mg/ml. The antimicrobial pharmacodynamics of the extract exhibited both concentration-dependent and time-dependent killing. Most of the test organisms exhibited a short post antibiotic effect (PAE) except Enterococcus faecalis, Staphylococcus aureus, and Klebsiella pneumoniae 1, which exhibited longer PAEs. Amongst the major phytoconstituents established, flavonoids, diterpenes, triterpenes and cardiac glycosides exhibited inhibitory properties against most of the test organisms. The identified active phytochemicals of the M. oleifera seed coat exhibited antimicrobial potential against a wide range of medically important pathogens including the multidrug-resistant bugs. Hence, the M. oleifera seed coat, which is usually regarded as an agri-residue, could be a source of potential candidates for the development of drugs or drug leads of broad spectrum that includes multidrug-resistant bugs, which are one of the greatest concerns of the $21^{st}$ century.

• The Journal of the Korean Society for Microbiology
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• v.35 no.5_6
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• pp.337-339
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• 2000

MRSA, erythromycin-resistant S. pyogenes, penicillin non-susceptible pneumococci, PPNG, ESBL-producing E. coli and K. pneumoniae, class C ${\beta}$-lactamase-producing E. coli, fluoroquinolone-resistant E. coli, aminoglycoside-resistant A. baumannii and P. aeruginosa are all prevalent in Korea, which suggest the presence of high levels of antimicrobial selective pressure and nosocomial spread of resistant bacteria. Rapid increase of VRE and emergence of fluoroquinolone-resistant gonococci and VIM-2 metallo-${\beta}$-lactamase-producing P. aeruginosa are recently observed new threats in Korea.

• Journal of Microbiology and Biotechnology
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• v.29 no.3
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• pp.465-472
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• 2019

Several reports describe antimicrobial-resistance transfer among children and the community in outbreak situations, but transfer between a child and a caregiver has not been examined in child care facilities under normal circumstances. We investigated the transfer of antimicrobial-resistance genes, resistant bacteria, or both among healthy children and teachers. From 2007 to 2009, 104 Escherichia coli isolates were obtained from four teachers and 38 children in a child care center. Twenty-six cephem-resistant isolates were obtained from children in 2007 and 2008. In 2009, cephem-resistant isolates were detected in children as well as a teacher. Nalidixic acid-resistant isolates from the same teacher for 3 years showed low similarity (<50%) to each other. However, an isolate from a teacher in 2007 and another from a child in 2008 showed high similarity (87%). Pulsed-field gel electrophoresis revealed 100% similarity for four isolates in 2007 and one isolate in 2008, and also similarity among seven isolates carrying the virulence gene (CNF1). This study yielded the following findings: (1) a gene for extended-spectrum ${\beta}$-lactamase was transferred from a child to other children and a teacher; (2) a nalidixic acid-resistant isolate was transferred from a teacher to a child; and (3) a virulent bacterium was transferred between children.