• The Plant Pathology Journal
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• v.40 no.5
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• pp.525-536
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• 2024

Agrochemicals containing antibiotics are authorized to manage fire blight that has been occurring in Korea since 2015. The minimum inhibitory concentration (MIC) of each antibiotic against Erwinia amylovora, the causal pathogen of fire blight, has increased over the years due to the pathogen's frequent exposure to antibiotics, indicating the necessity to prepare for the emergence of antibiotic resistance. In this study, E. amylovora was exposed to stepwise increasing concentrations of eight different agrochemicals, each containing single or mixed antibiotics, and gene mutation and changes in MIC were assessed. Streptomycin and oxolinic acid induced an amino acid substitution in RpsL and GyrA, respectively, resulting in a rapid increase in MIC. Oxytetracycline initially induced amino acid substitutions or frameshifts in AcrR, followed by substitutions of 30S small ribosomal protein subunit S10 or AcrB, further increasing MIC. E. amylovora acquired resistance in the order of oxolinic acid, streptomycin, and oxytetracycline at varying exposure frequencies. Resistance acquisition was slower against agrochemicals containing mixed antibiotics than those with single antibiotics. However, gene mutations conferring antibiotic resistance emerged sequentially to both antibiotics in the mixed formulations. Results suggested that frequent application of mixed antibiotics could lead to the emergence of multidrug-resistant E. amylovora isolates. This study provided essential insights into preventing the emergence of antibiotic-resistant E. amylovora and understanding the underlying mechanisms of resistance acquisition.

• Tuberculosis and Respiratory Diseases
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• v.42 no.3
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• pp.295-301
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• 1995

Background: The serious problems in retreatment of pulmonary tuberculosis are a significant proportion of drug resistance. Preferably retreatment should contain the drugs which has never used before, so drug retreatment is limited in selection. A new antibacterial substance, ofloxacin(OFX) is the activity against mycobacterium tuberculosis and it has been used in the treatment of pulmonary tuberculosis. The present report concerns the result of retreatment of pulmonary tuberculosis patients containing OFX treated at National Kongju Tuberculosis Hospital. Method: A retrospective study was made through the regular follow up of 92 smear positive cases, who were treated by four drugs regimen between Mar 1991 and June 1994 at National Kongju Tuberculosis Hospital. Four drugs were, namely prothionamide, cycloserine, ofloxacin and streptomycin(kanamycin or tuberactinomycin). The duration of follow up was over one year. Results: 1) Out of 92 cases with positive sputum AFB smear, 67(73%) achieved the negative conversion. 2) Considering the negative sputum conversion in all the groups, the vast majority(85%) of sputum conversion occurred within the first 4 months. 3) The roentgenological improvement occurred in 49 percent on the whole and when the extent of disease was minimal, moderately, far advanced pulmonary tuberculosis, sputum AFB smear negative response to retreatment was 100%, 93%, 68%, respectively. 4) When the duration of patient's illness was less than 1 year, 1 to 3 years, 3 to 5 years and more than 5 years, sputum AFB smear negative response to retreatment was 87%, 76%, 65% and 55%, respectively. 5) Adverse reaction to prothionamide, with complaints of gastrointestinal troubles was common and hepatic dysfunction without jaundice was observed in 7 percent, convulsion in 1 percent, that to cycloserine occurred renal dysfunction & psycosis & convulsion, 2%, 1%, 1%, respectively. Tinnitus with KM occurred in 1% and dirrhea with OFX in 4%. Conclusion: The duration of patient's illness was shorter, sputum AFB smear negative response rate was better. Radiologic responses were not remarkable, but extent of disease by national tuberculosis association was smaller, the result of retreatment was better. Adverse reaction of the secondary antituberculosis agent was mainly observed gastrointestinal troubles, as regard to tolerance to the secondary drugs the role of the physician is of very important value and toxic effects can be overcome by the strong confidence.

• Korean Journal of Soil Science and Fertilizer
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• v.22 no.3
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• pp.239-244
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• 1989

This work was for the elucidation of heterogeneity in a natural population of Rhizobium japonicum existing in Seoul National University's Experiment Field and of sensitivities of R. japonicum isolates for several antibiotics by using a method based on intrinsic antibiotic resistance (IAR). In addition, the suitability of IAR method for the recognition of R. japonicum strain was elucidated. Twenty seven isolates from various soybean cultivars cultivated at SNU's Experiment Field were tested to 4 antibiotics (streptomycin sulphate, kanamycin sulphate, ampicillin, oxytetracycline);There were 21 different IAR patterns among 27 isolates. It demonstrated diverse distribution of R. japonicum strains in SNU's Experiment Field. Their growth was inhibited at from a low concentration of about $1{\mu}g/ml$ to a high concentration of $400{\mu}g/ml$ for streptomycin sulphate, ampicillin, and oxytetracyclin. For kanamycin sulphate, on the contrary, all 27 isolates showed their growth inhibitances at below the concentration of $12.5{\mu}g/ml$. Two isolates identified as different strains from each other by the previous seroimmunological tests showed the same sensitivities for 4 antibiotics, and it seemed that IAR method was not perfect for the exact recognition of R. japonicum strain.

• Journal of Food Hygiene and Safety
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• v.13 no.3
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• pp.305-312
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• 1998

In order to investigate the species, serobiological characteristics and antibiotic sensitivity of Pseudomonas spp, we isolated Pseudomonas spp from 57 spring waters around Seoul area for spring, summer and autumn and identified Pseudomonas spp by biochemical characteristics and serological method. And also we tested the antibiotic sensitivity test by discdiffusion method. Of 57 spring waters tested, Pseudomonas spp were isolated from 33 spring waters(57.9%). Isolation rate of Pseudomonas spp in spring season was 28.1%, summer 21.1% and autumn 28.1%. Only 1 spring water was detected Pseudomonas spp in all seasons and 9 (15.8%) were detected for 2 seasons and 13 (22.8%) were for only 1 season. Isolation rate of Pseudomonas spp at Mt. Cheonggye was 50% and followed by Mt. Bookhan 35.7%, Mt. Daemo 33.3%, Mt. Dobong 29.6%, Mt. Surak 25.9%, Mt. Woomyun 22.2% and Mt. Bulam 7.4%. Of 44 Pseudomonas spp, 22 strains (50%) were identified by Ps. putida, Ps. aeruginosa, Ps. fluorescens and Ps. mendocina were identified 6 strains (13.6%), respectively. 4 strains (9.1%) were identified by Ps. aureofaciens. Of 6 Ps. aeruginosa, serotype A was 2 strains, B, E, G, and K was 1 strain, respectively. Of 44 Pseudomonas spp, resistance rate to amoxicillin was 90.9% and followed by chloramphenicol 84.1%, tetracycline 84.1%, carbenicillin 81.8%, nalidixic acid 68.2%, neomycin 38.6%, streptomycin 31.8%, gentamicin 4.6%, kanamycin 4.6% and colistin 2.3%. Ps. aeruginosa was more sensitive to carbenicillin than other Pseudomonas spp isolated from spring waters in Seoul area but more resistant to kanamycin, and Ps. aureofaciens was no resistant to streptomycin. Among multiple drug resistance, resistance to 5 drugs was 31.8%, 4 drugs 15.9%, 7 drugs 13.6%, 1 drug and 2 drugs 4.6%, and 8 drugs 2.3%, respectively. The multiple resistance patterns detected highestly were NA-CB-C-TE-AMC (18.2%), NA-CB-N-C-TE-AMC (13.6%), CBC-TE-AMC (11.4%) and NA-CB-N-C-TE-AMC-S (9.1%).

• Korean Journal of Environmental Biology
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• v.26 no.3
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• pp.240-246
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• 2008

From the 4 sampling stations located in the basin of the Han River, total 46 strains of Enterococcus spp. composed of 15 E. faecium strains, 26 E. casseliflavus strains, 1 E. faecalis strain and 4 E. hirae strains were isolated. Among the 46 strains, 45 strains exhibited streptomycin-resistance, while 21 and 19 stains were resistant against tetracycline and quinupristin/dalfopristin, respectively. As for gentamicin and vancomycin, 15 strains and 1 strain showed resistance against the respective antimicrobial agents. Among the 46 strains, 39 strains showed resistance against more than 2 antimicrobial agents, and 10 strains demonstrated resistance to more than 5 antimicrobial agents. Especially, the strain isolated from the station C at Anyangcheon, exhibited resistance against all the 8 kinds of the antimicrobial agents. As the sampling site approached to the lower stream of the Han-river, the antibiotic resistant strains and the multi-drug resistant strains were detected more frequently. The MIC values of the antibiotic resistant strains measured by the disc diffusion method disclosed that 16 strains possessed maximum MIC value of 4,096 ${\mu}g$ mL$^{-1}$ against streptomycin and 17 strains possessed maximum MIC value of 2,048 ${\mu}g$ mL$^{-1}$ against gentamicin. Meanwhile, 1 strain exhibited maximum MIC value of 5121 ${\mu}g$ mL$^{-1}$ against vancomycin. As for quinupristin/dalfopristin and tetracycline, 2 and 33 strains showed maximum MIC value of 641 ${\mu}g$ mL$^{-1}$, respectively. Comparison of the MIC values of the strains of the this study with those of the strains of the other research groups isolated from the hospital drainage and also those from the live stock farm drainage indicated that the strains resistant against vancomycin and quinupristin/dalfopristin may be originated from the livestock farm drainage.

• Journal of Microbiology and Biotechnology
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• v.6 no.3
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• pp.219-220
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• 1996

The pKH2 isolated from the multidrug-resistant Staphylococcus aureus SA2 is a 40.98-kb plasmid and mediates resistance to ampicillin, clindamycin, erythromycin, kanamycin, and streptomycin. The 3.4-kb HindIII fragment conferring kanamycin resistance was cloned from the pKH2 into pBluescriptII $KS^+$ and partial sequence determination of that fragment was carried out. Sequence analysis revealed that the kanamycin resistance gene which encoded aminoglycoside 3'-phosphotransferase was linked to the streptothricin resistance gene. But a nonsense mutation was found in the streptothricin resistance gene and this mutation resulted in a truncated protein of streptothricin acetyltransferase. Homology comparison with nucleotide sequence databases revealed that the 3.4-kb HindIII fragment of pKH2 had been derived not from S. aureus but from Gram-negative Campylobacter coli.

• Archives of Pharmacal Research
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• v.12 no.2
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• pp.119-124
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• 1989

Cotton xanthate, which was obtained by treating cotton with carbon disulfide in alkaline solution, was treated with the solution of polyvalent metal ions to produce cotton xanthate-metal chelates. This chelation reaction was readily and simply achieved, and antimicrobial agents with suitable structures could subsequently be coupled to the chelate with ease at moderate pH values and in aqueous solution. Metal ions used in present work include Cu(II), Zn(II) and Fe(III). Tetracycline, streptomycin, neomycin and pyrithion were used as antimicrobial/antifungal agents. Antibacterial activities were measured employing ditch plate method against G(+) Staphylococcus aureus, Streptococus faecalis, and G(-) Escherichia coli, Enterobacter aerogenes, and the fungus, Aspergillus niger. All the cotton xanthate-metal-antimicrobial agent chelates exhibited activities whereas the cotton xanthate-metal chelates themselves were inactive. Considering the extensive washing procedures and results from control experiments, possibility of the involvement of physical adsorption for the binding of drugs could be excluded.

• The Journal of the Korean Society for Microbiology
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• v.5 no.1
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• pp.27-31
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• 1970

Nalidixic acid and six other drugs were studied for in vitro effectiveness against 200 strains of Escherichia coli isolated recently from healthy persons and bactericidal activity of ampicillin against one respective strain of Escherichia coli and Salmonella typhi isolated were also studied. The resutlts obtained by the plate dilution method showed the following percentage of resistance: kanamycin, 2.5%; streptomycin, 12.0%; ampicillin, 13.5%; tetracyclin, 15.5%; chloramphenicol, 17.5%; colistin sulfate, 19.5%. No strains were resistant to nalidixic acid, clearly indicating that nalidixic acid is the most effective drug tested. Ampicillin, measured by test-tube diltion method, was highly bactericidal against Salmonella typhi at the concentration of 2.5mcg/ml and against Escherichia coli at 5mcg/ml.

• Toxicological Research
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• v.13 no.1_2
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• pp.111-116
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• 1997

In the present study, we investigated the neutralization activity of various antimicrobials against lipopolysaccharide (LPS) as well as interaction between two antimicrobials (enrofioxacin and coilstin) using checkerboard method. The neutralization activity of antimicrobials used in the test was assayed by means of LAL chromogenic test after reaction of LPS with colistin, enorfioxacin, ampicillin, polymyxin B, oxytetracycline, streptomycin, and erythromycin. As the results, the neutralization activity of coltstin and polymixin B had a more stronger than that of tested other antimicrobials. In bacterial culture broth, the best neutralization activity of the antibiotics was also shown to coltstin and polymixin B. Meanwhile, It was shown to have synergism between enorfloxacin and coltstin on the basts of FIC (fractional inhibition concentration). The FIC of enorfioxacin-colistin combinations was 0.50-1.03 to Staphylococcus aureus R-209, 1.03-1.06 to Salmonella typhimurium, 0.75-1.25 to Bordetella Bronchtseptica and 1.02-1.25 to E. coli K88ab. On the basts of the above results, the present study may be of clinical usefulness in the choice of an antibiotic therapy for severe sepsts in animals.

• Korean Journal of Veterinary Research
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• v.15 no.1
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• pp.69-73
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• 1975

A Total of 173 streptococci isolated from 536 dairy cattle in Gyeonggi Province identified by Lancefield serological reaction and other biological properties. Antibiotics sensitivity test was also examined and the results obtained were as follows: 1. A total of 173 isolates of 167 strains (96.5%) were reacted with group A,B,C,D,E and G antisera. 2. Of the 167 positive strains, 75 strains were identified to Streptooccus uberis, 56 to Streptococcus agalactiage and 26 to Streptococcus dysgactiae, respectively. Also, Sreptococcus pyogenes, group D and group G streptococci were rarely isolated. 3. In results of antibiotic sensitivity tests, the most isolates were sensitive to leucomycin and erythromycin but less sensitive to streptomycin. and kanamycin.