• The Journal of the Korean Society for Microbiology
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• v.16 no.1
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• pp.19-28
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• 1981

The Pseudomonas infection has been increased in incidence and suspected as a cause of opportunistic pathogen. Protease and elastase produced by Pseudomonas aeruginosa are reported to be closely associated with pathogenicity of Pseudomonas aeruginosa. We examined, in this work, the relationship between production of exoenzyme of Pseudomonas aeruginosa and susceptibility to antimicrobial agents in view of possible application to the management of Pseudomonas infection. 1. In 295 Pseudomonas aeruginosa isolated from clinical specimens, 34.6% were from pus, 20.7% from sputum, 15.6% from wound including burn sites and 12.9% from urine. 2. Distribution of protease and elastase production by clinically isolated Pseudomonas aeruginosa, showed that protease and elastase producing strains were 83.1%, protease producing strains were 7.5%, elastase producing strains were 2.0%, and non producing strains were 7.5%. 3. MIC(minimum inhibitory concentration) peak for tetracycline and chloramphenicol were observed at 25mcg/ml and 200mcg/ml respectively, but there were no Pseudomonas aeruginosa which correspond to MIC peak, 6.25mcg/ml. Gentamicin of aminoglycosides was highly susceptible to Pseudomonas aeruginosa clinically isolated from pus, sputum and wound sites, but susceptible to isolates from nasal discharge and urine. Regarding MIC peak of carbenicillin, 100mcg/ml, 81.8% of Pseudomonas aeruginosa were from urine, 54.8% from wound including burn sites, 52.7% from pus, and 50.8% from sputum. 4. Enzyme producing strains showed no susceptibility to kanamycine and carbenicillin at low concentration, but protease producing strains tend to resistant to antimicrobial agents.

• Biomedical Science Letters
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• v.5 no.2
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• pp.213-217
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• 1999

In order to control resistant strains and to properly select the antimicrobial agents, it is of quite importance to know current trends of bacterial species and changing patterns of antimicrobial resistance rates. The authors studied the results of 542 Gram-positive strains among 1,689 strains isolated at Chung-buk National University Hospital in 1996. The frequently isolated Gram-positive microorganisms were Staphylococcus aureus, Streptococcus pneumoniae, Staphylococcus epidermidis and Enterococcus faecalis in descending order. S. aureus showed high resistance to penicillin, gentamicin, and susceptibility to teicoplanin and vancomycin. Coagulase negative Staphylococcus was highly resistant to all of the antibiotics used in this experiment except teicoplanin and vancomycin. Enterococcus were highly resistant to vancomycin, penicillin and tetracycline. MIC of Gram-positive oaganisms was appeared to be zig-zag pattern.

• Journal of Veterinary Clinics
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• v.38 no.5
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• pp.225-230
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• 2021

A 4-year-old gelding Thoroughbred racehorse, which had been undergoing antibiotic therapy at a local veterinary clinic, was referred to the KRA veterinary center with a 20-day history of continuous right nasal discharge. Patient's history, endoscopic examination, and radiographic examination revealed primary maxillary sinusitis. Under sedation, surgical intervention was performed to collect samples and remove the accumulated mucopurulent exudate in the sinus. Swab samples were collected from the sinus during surgery for cytology and antimicrobial susceptibility testing. Only one type of bacteria was cultured, and molecular analyses of 16S ribosomal RNA gene sequences identified it as Staphylococcus aureus (S. aureus). The isolate was resistant to multiple antibiotics, which are frequently used in equine practice. Trimethoprim-sulfamethoxazole was chosen based on antibiotic susceptibility test, trephination, and sinus lavage using saline were applied to treat bacterial sinusitis. The clinical signs improved after 1 month and the patient resumed training. This report describes S. aureus isolated from bacterial maxillary sinusitis in a horse and its antibiotic susceptibility.

• Korean Journal of Veterinary Service
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• v.35 no.4
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• pp.295-305
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• 2012

The aim of this study was to isolate microorganisms from half milk samples of dairy goats by California mastitis test (CMT) during the lactation period and to further investigate the susceptibility of isolated organisms to antimicrobial drugs. From a total of 235 half milk samples with CMT scores of 2 or above from 366 dairy goats distributed throughout Jeonnam province, microorganisms were isolated from 198 (83.5%) samples either singly (99.0%) or in combination (1.0%). The most prevalent microorganism was the coagulase-negative Staphylococcus spp., (44.4%, n=88) followed by Staphylococcus aureus (24.2%, n=48), Escherichia coli (11.1%, n=22) and Streptococcus spp. (7.6%, n=15). Isolated bacteria also included Bacillus spp. (2.5%, n=5), Pseudomonas spp. (2.5%, n=5), Micrococcus spp. (1.5%, n=3), Corynebacterium spp. (1.5%, n=3), Enterococcus facium (1.0%, n=2), Morganella morganii (0.5%, n=1) and Streptococcus agalactiae (0.5%, n=1). During the summer season, a high prevalence of all microorganisms were observed in which Staphylococcus spp. (30.8%), Escherichia coli (8.6%), and Streptococcus spp. (5.6%) were among the most prevalent bacteria isolated. Staphylococcus spp. was also shown to be high in the winter (21.7%). In most samples, the presence of bacterial pathogens in goat milk led to the increase in the total somatic cell count (SCC). Most of the half milk samples of dairy goats with bacterial contamination showed SCC of ${\geq}1{\times}10^6cells/ml$ (90.4%). Minor pathogens (11.4%) were more detected from milk samples with SCC of < $1{\times}10^6cells/ml$ than major pathogens (4.1%), while the major pathogens tended to be higher from samples with SCC of ${\geq}3{\times}10^6cells/ml$. Susceptibility of these bacteria to 12 antimicrobial agents was tested by the Kirby-Bauer disc diffusion method. Results indicated that more than 90% of bacteria isolated from CMT 2+ dairy goat half milk samples were susceptible to trimethoprim/sulfamethoxazole, amoxicillin/clavulanic, enrofloxacin and cephalothin while they were resistant to tetracycline (44.7%).

• Journal of Life Science
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• v.20 no.10
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• pp.1549-1555
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• 2010

Streptococcus suis is a worldwide pathogen of a variety of porcine infection and has also been described as a pathogen for humans. We studied biochemical characteristics, antimicrobial susceptibility, and identification of polymerase chain reaction (PCR) of S. suis isolated from diseased pigs in Gyeongbuk province from 2004 to 2009. Sixty-one isolates were identified as S. suis by biochemical characteristics and PCR from 40 farms. The biochemical characteristics of S. suis isolates were production of VP-negative, hippurate, esculin, and arginine decarboxylase-positive, and fermentation of carbohydrate was variable lactose, trehalose, inulin, and raffinose, which was typeable 11 phenotype. In an antimicrobial susceptibility test, the majority of isolates were highly susceptible to amoxicillin/clavulanic acid, ampicillin, cephalothin, cefoperazone and florfenicol, while being highly resistant to streptomycin, kanamycin, amikacin, neomycin, erythromycin, clindamycin, and tetracycline. The isolates were divided into 11 phenotypes of biochemistry. By using PCR, the 16S-rRNA gene DNA fragment was detected at 304 bp from all of isolates. These results may provide the basic information needed to establish strategies for the prevention of S. suis infection in pigs.

• Journal of Microbiology and Biotechnology
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• v.28 no.3
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• pp.381-390
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• 2018

We have previously derived a novel antimicrobial peptide, LPcin-YK3(YK3), based on lactophoricin and have successfully studied and reported on the relationship between its structure and function. In this study, antimicrobial peptides with improved antimicrobial activity, less cytotoxicity, and shorter length were devised and characterized on the basis of YK3, and named YK5, YK8, and YK11. The peptide design was based on a variety of knowledge, and a total of nine analog peptides consisted of one to three amino acid substitutions and C-terminal deletions. In detail, tryptophan substitution improved the membrane perturbation, lysine substitution increased the net charge, and excessive amphipathicity decreased. The analog peptides were examined for structural characteristics through spectroscopic analytical techniques, and antimicrobial susceptibility tests were used to confirm their activity and safety. We expect that these studies will provide a platform for systematic engineering of new antibiotic peptides and generate libraries of various antibiotic peptides.

• Food Science of Animal Resources
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• v.36 no.4
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• pp.487-493
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• 2016

The antimicrobial activity of bovine lactoferrin hydrolysates (bLFH) was measured against Pseudomonas strains (P. syringae and P. fluorescens) in vitro. To compare susceptibility to bLFH, minimal inhibitory concentration (MIC) values were determined using chemiluminescence assays and paper disc plate assays. Antimicrobial effect against P. fluorescens was not observed by either assay, suggesting that bLFH did not exhibit antimicrobial activity against P. fluorescens. However, a significant inhibition of P. syringae growth was observed in the presence of bLFH. The addition of bLFH in liquid or solid medium inhibited growth of P. syringae in a dose-dependent manner. Furthermore, a bLFH peptide with antimicrobial activity toward P. syringae was isolated and identified. The N-terminal amino acid sequences of thus obtained antimicrobial bLFH peptides were analyzed by a protein sequencer and were found to be Leu-Arg-Ile-Pro-Ser-Lys-Val-Asp-Ser-Ala and Phe-Lys-Cys-Arg-Arg-Trp-Gln-Trp-Arg-Met. The latter peptide sequence is known to be characteristic of lactoferricin. Therefore, in the present study, we identified a new antimicrobial peptide against P. syringae, present within the N-terminus and possessing the amino acid sequence of Leu-Arg-Ile-Pro-Ser-Lys-Val-Asp-Ser-Ala.

• Journal of Microbiology and Biotechnology
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• v.24 no.7
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• pp.1008-1013
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• 2014

The use of antimicrobial agents for additives or therapeutics is strongly associated with a prevalence of antimicrobial resistance in commensal Enterobacteriaceae. We aimed to characterize integrons in Enterobacteriaceae isolates obtained from chicken cecums in Korea. Moreover, the correlation between integron gene cassettes and antimicrobial resistance was also investigated. A total of 90 isolates the belonged to Enterobacteriaceae were recovered from chickens grown at Gyeongsang and Chungcheong provinces in Korea. Antimicrobial susceptibility tests were performed by the disk diffusion method. PCR and DNA sequencing were also performed to characterize the gene cassette arrays of the integrons. Of the 90 Enterobacteriaceae isolates tested, 39 (43.3%) and 10 (11.1%) isolates carried class 1 and 2 integrons, respectively. Whereas the class 2 integron did not contain gene cassettes, the class 1 integrons carried seven different gene cassette arrays. The class 1 integrons harbored genes encoding resistant determinants to aminoglycosides (aadA1, aadA2, and aadA5), trimethoprim (dfrA1, dfrA12, dfrA17, and dfrA32), lincosamides (linF), and erythromycin (ereA). Moreover, the presence of a class 1 integron was significantly related to a high resistance rate of antimicrobial agents, such as spectinomycin and trimethoprim. We confirmed that diverse class 1 integrons were widely distributed in Enterobacteriaceae isolates from chickens and directly contributed to the resistance to diverse antimicrobial agents in Korea.

• The Plant Pathology Journal
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• v.35 no.2
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• pp.149-155
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• 2019

The antimicrobial activity of acetone, hexane, dichloromethane, and methanol extracts from leaves, stems, immature green fruits, and red fruits of tomato plants was examined against six phytopathogens. The minimum inhibitory concentration (MIC) of the acetonic extracts from these four plant parts was lower than that of the other solvents. Among the acetonic extracts, tomato leaves had a lower MIC than the other tomato parts. The acetonic extract from tomato leaves was therefore selected as a source of antimicrobial substances. The acetonic extract from tomato leaves inhibited mycelial growth of Fusarium oxysporum f. sp. lycopersici, Glomerella cingulata, and Rhizoctonia solani. Mycelial growth of R. solani treated with acetone extract from leaves showed more susceptibility than the other phytopathogens. Using 0.31 mg/ml of the acetonic extract from leaves, mycelial growth of R. solani on days 1, 2, and 3 decreased by 50.0, 52.1, and 64.0%, respectively, compared with acetone solvent treatment. The antimicrobial compounds effective against R. solani were identified as linolenic acid and caffeic acid by bioautography and GC-MS. These two compounds were used to treat six phytopathogens to confirm their antimicrobial activities. Linolenic acid inhibited mycelial growth of R. solani, while caffeic acid showed only slight antimicrobial activity. Results indicated that we propose extracts from tomato leaves which included antimicrobial compounds may provide a new lead in the pursuit of new biological sources of agrochemical candidates.

• Journal of Microbiology and Biotechnology
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• v.13 no.6
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• pp.998-1000
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• 2003

This study was carried out to elucidate the mode of bacteriostatic property of xanthostatin (XS), a novel depsipeptide antibiotic with an N-acetylglycine side chain and selective antimicrobial activity against Xanthomonas spp. Two biotransformed XSs were isolated by the treatment of XS with the cell lysate of Xanthomonas campestris pv. citri, a solvent partition, preparative TLC, and HPLC. Structure determination of those two biotransformed XSs demonstrated deletion of the N-acetylglycine side chain. Noteworthily, they showed no antimicrobial activity against Xanthomonas spp. This result suggests that the N-acetylglycine side chain plays a critical role in the antimicrobial activity of XS, and that the bacteriostatic property of XS is due to susceptibility of the ester bond between the hexadepsipeptide nucleus and the N-acetylglycine side chain to hydrolytic enzyme(s) produced by Xanthomonas spp.