• Korean Journal of Veterinary Research
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• v.21 no.1
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• pp.25-31
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• 1981

A total of 250 enteric bacteria (148 Escherichia coli, 41 Klebsiella pneumoniae, 46 Enterobacter spp. and 15 Proteus spp.) isolated from bovine udder infections in 1979 through 1980 were examined for drug resistance and prevalence of R. plasmids. The drug tested were streptomycin (SM), kanamycin (KM), ampicillin (AP), chloramphenicol (CP), tetracycline (TC), gentamicin (GM), oxolinic acid (OA) and nalidixic acid (NA). The detection of R. plasmids was performed with Escherichia coli ML 1410 NAr as the recipient. Of the 148 Escherichia coli isolated, 68(45.9%) were found to be resistant to one or more drugs tested, and about 50% of the resistant strains were multiply resistant. of the 68 drugresistant strains, 13(19.1%) were found to carry R. plasmids which were capable of performing a conjugal transfer. CP resistance was transfered together with the other resistance. Of 41 strains of Klebsiella pneumoniae isolated, 90.2% were resistant to the drugs, alone or in combination thereof. Strains resistant to AP and TC were 63.4%, and 48.8%, respectively. R. plasmids were detected in 78.4% of the drug-resistant strains, and these strains transfered all or a part of their drug resistance pattern. AP and CP resistance were transfered in 100% of AP and CP-resistant strains. Eleven (37.9%) of 29 R. plasmids showed a thermosensitive transfer. Of the 46 strains of Enterobacter spp. isolated, 37(80.4%) were resistant to the drugs tested. A high percentage of resistance was noted for AP(65.2%). All strains resistant to four or more drugs transferred their resistances to Escherichia coli ML 1410, but strains resistant to three or fewer drugs did not transfer the resistances. All of the 15 Proteus strains isolated were resistant to more than two drugs. of them, 6 were quadruple resistance to SM, KM, CP and TC, and 9 were double one to AP and TC. Three (20.0%) of the drug-resistant isolates had R.plasmids conferring AP and TC resistance. GM, OA and NA of the drugs tested were very active to all of 250 Gram-negative enteric bacteria isolated from bovine udder infections.

• Research in Plant Disease
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• v.10 no.1
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• pp.58-62
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• 2004

Contamination level and characteristics of Ralstonia solanacearum in soil of greenhouses cultivating tomato plants in Chungbuk province was determined. R. solanacearum was isolated with the semiselective media in 27 greenhouse soil samples out of 133 greenhouses soil investigated, which indicates 20.3 ％ of tomato cultivating greenhouses in Chungbuk contaminated with the bacterial wilt pathogen. Density of R. solanacearum was estimated to 10$^{2.4}$ cfu/g in the contaminated soil. All 71 isolates of R. solanacearum which containing 12 isolates from the diseased tomato plants were race 1, ann 35 isolates of them were biovar 3 and 36 isolates were biovar 4. More than 88％ of 71 isolates were inhibited growth on nutrient agar containing oxolinic acid 0.5 $\mu\textrm{g}$/ml, streptomycin 25 $\mu\textrm{g}$/ml, tetracycline 5 $\mu\textrm{g}$/ml and cupric sulfate 375 $\mu\textrm{g}$/ml (1.5 mM). The 11.3％, 4.2％ and 5.6 ％ of the isolates can grow on nutrient agar containing 10 times more oxolinic acid, streptomycin, tetracycline than minimal inhibitory concentration of the sensitive strains. Five isolates were resistant to 2 bactericides and one isolates was resistant to all 3 bactericides.

• Research in Plant Disease
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• v.30 no.2
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• pp.199-205
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• 2024

Erwinia amylovora, a causal pathogen of fire blight, has been continuously inducing damage to the apple and pear trees in South Korea since 2015. Farmers apply antibiotics during blooming season to prevent the fire blight. However, continuous use of antibiotics can induce the emergence of resistant bacteria, which consequently reduces control efficacy. In this study, we assessed the minimal inhibitory concentration (MIC) of streptomycin, using a total of 361 E. amylovora isolates that were collected from the six provinces of South Korea from 2019 to 2023. As a result, the MIC of streptomycin ranged from 0.5 to 4 ㎍/ml and the strA-strB genes were not identified from the isolates. The MIC was higher in the isolates from Gyeonggi-do, Gangwondo, and Chungcheongbuk-do compared to those from other three provinces. These results may bring broad attention to the use of streptomycin and aid in developing a management protocol for the occurrence of fire blight in South Korea.

• Journal of Microbiology and Biotechnology
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• v.20 no.6
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• pp.1042-1052
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• 2010

Forty-seven Salmonella Typhimurium (33 zoonotic, 14 clinical) strains were tested for antimicrobial resistance using the standard disk diffusion method. The presence of relevant resistance genes and class 1 integrons were investigated by using PCR. Pulsed-field gel electrophoresis (PFGE) and plasmid profiling were carried out to determine the genomic diversity of Salmonella Typhimurium. Approximately 57.4% of the S. Typhimurium strains were multidrug resistant (MDR) and showed high resistance rates to tetracycline (70.2%), sulfonamides (57.4%), streptomycin (53.1%), ampicillin (29.7%), nalidixic acid (27.6%), kanamycin (23.4%), chloramphenicol (21.2%), and trimethoprim (19.1%). Resistance towards cephalosporins was noted for cephalothin (27.6%), cephradine (21.2%), amoxicillin clavulanic acid (17.0%), and cephalexin (17.0%). Resistance genes, $bla_{TEM}$, strA, aadA, sul1, sul2, tetA, tetB, and tetC, were detected among the drug-resistant strains. Thirtythree strains (70.2%) carried class 1 integrons, which were grouped in 9 different profiles. DNA sequencing identified sat, aadA, pse-1, and dfrA genes in variable regions on class 1 integrons. Thirty-five strains (74.4%) were subtyped to 22 different plasmid profiles, each with 1-6 plasmids (2.0 to 95 kb). PFGE subtyped the 47 strains into 39 profiles. In conclusion, high rates of multidrug resistance were found among the Malaysian Salmonella Typhimurium strains. The emergence of multidrug-resistant Salmonella Typhimurium to cephalosporin antibiotics was also observed. The strains were very diverse and no persistent clone was observed. The emergence of MDR Salmonella Typhimurium is a worldwide problem, and this report provides information for the better understanding of the prevalence and epidemiology of MDR S. Typhimurium in Malaysia.

• The Journal of the Korean Society for Microbiology
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• v.22 no.3
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• pp.295-300
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• 1987

Salmonella strains isolated from blood in the Dong-san hospital, Taegu during the period from 1971 to 1986 were studied for species distribution, drug resistance, and R plasmids. The number of strains was 2,527 and all of them were classified into S. typhi and S. paratyphi A. Approximately 300 strains were isolated in the period from 1974 to 1976 and 1978, 268 in 1982, and 204 in 1983, but the numbers isolated in the 1980's have a tendency to decrease as compared with those of the 1970's. S. typhi occupied 85% or more of strains isolated until 1976, but the isolation frequency decreased yearly with some variation, and S. paratyphi A increased gradually from 1974. Only 4 strains of S. paratyphi A were resistant to some drugs, and the resistance was not transferred to E. coli by conjugation. S. typhi resistant to drugs were 15 in 1971 through 1973, 24 in 1974, and 13 in 1975, but afterwards only few resistant strains were isolated. These strains were resistant to two or more drugs; chloramphenicol(Cm), tetracycline(Tc), streptomycin(Sm), sulfisomidine(Su), ampicillin(Ap), and kanamycin(Km) and no strain resistant to other drugs tested was found. Strains resistant to 3 or less drugs didn't transfer the resistance to E. coli by conjugation. There were 15 strains resistant to four or more drugs, and were isolated in years from 1972 to 1976. These strains transferred the resistance to E. coli, and the resistance was considered to be mediated by R plasmids. Transfer frequency was higher at $25^{\circ}C$ than at $37^{\circ}C$ and patterns of transferred resistance were Cm, Tc, Sm, Su; Ap, Km; Cm. R plasmids having markers of Cm, Tc, Sm and Su were classified into Inc H1.

• Microbiology and Biotechnology Letters
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• v.37 no.3
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• pp.258-265
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• 2009

A study on livestock environment improving agents was conducted; top two brands (A and B) in the market, bottom two brands (E and F) based on market shares and two newly developed agents (C and D) were measured for viable count and tested for resistance towards antibiotics prohibited against livestock feeds. Test results revealed that the measured viable count of agents A and B matched those on the labels were identical; however agent E lacked information on viable counts nor the intended usage, while the measured viable count of agent F was less than the label-stated count. No correlation was found between the antibiotic-resistance test and market share, and most of the agents excluding B were found to display resistance case of Lincosimides such as Lincomycine and Clindmycin, resistant bacteria were found, with the except of agent B. Amoxicillin, Ampicillin and Penillin (type-Penecillins) and Erythromycin (type-Macrolide) were shown to contain resistant bacteria, with the except of agents Band E; the same for Norploxacin (type-Quinoline) and Neomycin antibiotics. Aminoglycosides such as Gentamycin and Streptomycin contained resistant bacteria, excluding agent B. Oxytetracyclin (type-Tetracycline), which is banned for use as resistant bacteria showed the highest sensitivity among the 12 antibiotics, revealed positive results in the test for resistant bacteria; again excluding of agents Band E. These results reveal that many agents contained resistant bacteria despite the fact that they were prohibited; this calls for a more accurate display of the facts and specifications, systematic distributions and strict verification processes of environment improving agents.

• Microbiology and Biotechnology Letters
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• v.36 no.2
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• pp.142-148
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• 2008

To evaluate the antibiotic resistance of Enterococcus from salad and sprout, Enterococcus were isolated and identified from 47 salad samples and 37 sprout samples, and then their antibiotic resistances were analyzed. Ninety five Enterococcus, 41 strains from salad and 54 strains from sprout, were ultimately isolated. The frequent Enterococcus in salad and sprout were E. gallinarum, E. faecalis, E. faecium, E. hirae, and E. avium. Minimum inhibitory concentrations of the isolates for vancomycin were below $4{\mu}g/mL$, which were not high levels of resistance. All Enterococcus proved to be resistant to streptomycin and chloramphenicol. Twenty two percentage of the isolates were resistant to penicillin, however, almost the isolates were sensitive to tetracycline. Eighteen percentage of the isolates were resistant to erythromycin. All E. faecium and E. faecalis were found to be ampicillin-resistant, and seven E. faecalis and five E. faecium were resistant to rifampicin. Overall antibiotic resistances of Enterococcus isolates were relatively low and low resistance to vancomycin was similar to those evidenced by Enterococcus isolated from the other foods. Therefore, there may be no special risk from the antibiotics resistances of Enterococcus and especially vancomycin-resistant Enterococcus from the fresh-cut salads and the sprouts.

• Korean Journal of Environmental Biology
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• v.29 no.4
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• pp.286-295
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• 2011

Bacteria resistant to various antibiotics have recently become an issue of the utmost importance. Resistant strains are not uncommon, even in municipal drinking water sources. The health threat posed by resistant, pathogenic bacteria has serious ramifications for both public health and agriculture. In this study, we isolated antibiotic resistant bacteria from water samples from the Han River, Korea, which is contaminated by the wastewater from many industrial complexes, hospitals, agricultural and animal husbandry estates, and from wastewater treatment facilities. We determined the degrees of resistance to various antibiotics exhibited by the isolated strains. The similarities between the isolated $E.$ $coli$ strains were examined, using the pulsed field gel electrophoresis and multilocus sequence typing, in order to trace their origins and to explore the syntechnic adaptations and pathogenicity of the various strains and relate these to their genetic sequence. A total of 25 $E.$ $coli$ strains were isolated from six stations along the Han River. All the 25 strains exhibited resistance to ampicillin. We also investigated resistance to amoxicillin, clavulanic acid, cefazolin, cofoxitin, cefotaxime, cefpodoxime, ceftriaxone, cefepime, nalidixic acid, aztreonam, ciprofloxacin, streptomycin, gentamicin, chloramphenicol and imipenem. Based on the ESBL detection, 14 strains belonged to the ESBL producing strains. The number of the clonal complex producing strains was 5 among the 14 isolated strains. The 5 strains were included in the 168, 23, 38, 469, 156 clonal complex, respectively. The rest 9 strains were not included in the clonal complex, but showed independent STs.

• Journal of environmental and Sanitary engineering
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• v.22 no.4
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• pp.55-63
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• 2007

We investigated the distribution and drug susceptibility test of V. vulnificus isolated from environmental sources in Incheon. In this survey, total 4,302 samples were obtained from different sites of the Incheon coastal area during the periods from march 2004 to November 2006. Among the 4,302 samples, 310 strains were isolated. The isolation rates of Vibrio vulnificus from fish, shellfish, estuarine water and sediment were 6.7%, 4.7%, 12.4% and 23.2%, respectively. The highest isolation rate was 14.6% in September and in spite of low temperature the isolation rate was 5.1% in November. The highest rate of antibiotic resistance was observed against streptomycin(15.3%), cefazolin(8.5%), cephalothin(8.3%), amikacin(8.3%), cefoxitin(6.7%) and nalidixic acid(6.7%). Seventeen percent of isolates were observed to be resistant to two or more of the antibiotics tested.

• Journal of Microbiology and Biotechnology
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• v.13 no.6
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• pp.872-880
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• 2003

Three vectors, pSG1, 2, and 3, which facilitate in vivo expression technology (IVET) in Gram-negative bacteria, were developed. Vectors pSG1and 2 are derivatives of ColE1, and pSG3 is a derivative of an R6K replicon. These vectors contain oriT sites that allow mobilization when the RK2 Tra functions are provided in trans. These vectors contain promoterless lacZ (pl-lacZ) and promoterless aph (pl-aph) transcriptionally fused together, which allow qualitative and quantitative measurements of the expression of genes in the genome of bacterial cells. pSG1 and 3 contain gentamicin-resistance genes, and pSG2 carries a streptomycin-/spectinomycin-resistance gene, allowing for selection of recombinants generated by a single crossover between a library fragment cloned into a pSG vector and the identical region in the genome of a bacterial species from which the library fragment originated. These vectors were successfully applied to the generation of random fusions at high rates in the genomes of four representative Gram-negative bacteria. In addition, the expression level of ${\beta}-galactosidase$ and the degree of resistance to kanamycin in cells with fusions generated by these vectors were found to be linearly correlated, proving that these vectors can be used for IVET.