• Korean Journal of Veterinary Service
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• v.45 no.3
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• pp.181-189
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• 2022

Streptococcus is one of the major pathogen groups inducing bovine mastitis. The aim of this study was to investigate the antimicrobial resistance patterns of Streptococcus species isolated from bovine mastitis milk samples in Korea from 2016 to 2021. In total, 181 (10.3%) Streptococcal isolates were collected from 1,761 quarter milk samples at 122 farms; S. uberis 39.2% (n=71), S. dysgalactiae 29.3% (n=53), S. equinus 9.9% (n=18), S. suis 6.1% (n=11), S. parauberis 4.4% (n=8), S. lutetiensis 3.9% (n=7), others 7.2% (n=13). However, S. agalactiae was not isolated. The isolates showed the highest resistance rate to tetracycline (55.2%) followed by erythromycin (45.3%) and pirlimycin (36.5%). In contrast, all isolates were susceptible to ceftiofur, cephalothin, penicillin/novobiocin, and only single S. equinus isolate was resistant to both ampicillin and penicillin. Of 181 isolates, 64 (35.4%) were multidrug resistance (MDR). The resistance to pirlimycin of S. uberis (73.2%) was much higher than that of other species (0~36.4%). All S. suis isolates were resistance to tetracycline. S. dysgalactiae showed lower resistance to erythromycin, pirlimycin and tetracycline than S. uberis and S. suis. The rate of MDR was relatively higher among S. uberis (73.2%) than among S. suis (36.4%), S. dysgalactiae (15.1%), others (0%). In conclusion, antimicrobial resistance in Streptococcus spp. should be regularly examined for appropriate therapies because the resistance patterns were various among the individual species.

• Microbiology and Biotechnology Letters
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• v.50 no.1
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• pp.81-88
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• 2022

Acetic acid bacteria (AAB) are versatile organisms involved in the production of variety of fermented foods, such as vinegar and kombucha, and products of biotechnological relevance, such as bacterial cellulose. In the present study, Malatya apricot, a variety with protected designation of origin (PDO), and vinegar samples produced using various fruits were used to isolate AAB. The 19 AAB isolates obtained were typed using (GTG)5 fingerprinting, and the ones selected were identified by sequencing either 16S rDNA alone or in combination with 16S-23S rRNA internal transcribed spacer region or ligA gene. While all apricot isolates (n = 10) were Gluconobacter cerinus, vinegar isolates (n = 9) were composed of Komagataeibacter saccharivorans, Acetobacter syzygii, and possible two new species of AAB, Komagataeibacter sp., and Gluconobacter sp. (GTG)5 fingerprinting showed the presence of several genotypes of G. cerinus in the apricot samples. Screening for some technologically relevant properties, including thermotolerance, ethanol tolerance, and cellulose production capability, showed that all Komagataeibacter and some Gluconobacter isolates could tolerate the temperature of 35℃, and that vinegar isolates could tolerate up to 8% ethanol. One isolate, Komagataeibacter sp. GUS3 produced bacterial cellulose (1 g/l) and has the potential to be used for cellulose production.

• The Plant Pathology Journal
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• v.24 no.3
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• pp.337-351
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• 2008

Host-pathogen interaction in rice bacterial blight pathosystem was analyzed for a better understanding of their relationship and recognition of stable pathogenicity among the populations of Xanthomonas oryzae pv. oryzae. A total number of 52 bacterial strains isolated from diseased leaf samples collected from 12 rice growing states and one Union Territory of India, were inoculated on 16 rice varieties, each possessing known genes for resistance. Analysis of variance revealed that the host genotypes(G) accounted for largest(78.4%) proportion of the total sum of squares(SS), followed by 16.5% due to the pathogen isolates(I) and 5.1% due to the $I{\times}G$ interactions. Application of the Additive Main effects and Multiplicative Interaction(AMMI) model revealed that the first two interaction principal component axes(IPCA) accounted for 66.8% and 21.5% of the interaction SS, respectively. The biplot generated using the isolate and genotypic scores of the first two IPCAs revealed groups of host genotypes and pathogen isolates falling into four sectors. A group of five isolates with high virulence, high absolute IPCA-1 scores, moderate IPCA-2 scores, low AMMI stability index '$D_i$' values and minimal deviations from additive main effects displayed in AMMI biplot as well as response plot, were identified as possessing stable pathogenicity across 16 host genotypes. The largest group of 27 isolates with low virulence, small IPCA-1 as well as IPCA-2 scores, low $D_i$ values and minimal deviations from additive main effect predictions, possessed stable pathogenicity for low virulence. The AMMI analysis and biplot display facilitated in a better understanding of the host-pathogen interaction, adaptability of pathogen isolates to specific host genotypes, identification of isolates showing stable pathogenicity and most discriminating host genotypes, which could be useful in location specific breeding programs aiming at deployment of resistant host genotypes in bacterial blight disease control strategies.

• Research in Plant Disease
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• v.26 no.1
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• pp.44-47
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• 2020

Streptomycin resistant isolates of Pseudomonas syringae pv. actinidiae, the causal agent of bacterial canker in kiwifruit, were found in Korea. A total of 734 isolates of P. syringae pv. actinidiae collected between 2008 and 2017 from bacterial canker infections in 111 kiwifruit orchards were assessed for streptomycin resistance. The survival of each isolate was screened against 100 ㎍/ml of streptomycin. Among 734 isolates, 38 streptomycin resistant P. syringae pv. actinidiae isolates originated from nine orchards were found. Streptomycin resistant isolates belonging to biovar 2 were found in several individual years, but ones belonging to biovar 3 were found in Korea only since 2016. Therefore, to use streptomycin for control of bacterial canker in kiwifruit orchards should be very careful, and it is necessary to check the streptomycin susceptibility of the pathogen before use in kiwifruit orchards.

• Annals of Laboratory Medicine
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• v.38 no.6
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• pp.555-562
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• 2018

Background: The emerging mobile colistin resistance gene, mcr-1, is an ongoing worldwide concern and an evaluation of clinical isolates harboring this gene is required in Korea. We investigated mcr-1-possessing Enterobacteriaceae among Enterobacteriaceae strains isolated in Korea, and compared the genetic details of the plasmids with those in Escherichia coli isolates from livestock. Methods: Among 9,396 Enterobacteriaceae clinical isolates collected between 2010 and 2015, 1,347 (14.3%) strains were resistant to colistin and those were screened for mcr-1 by PCR. Colistin minimum inhibitory concentrations (MICs) were determined by microdilution, and conjugal transfer of the mcr-1-harboring plasmids was assessed by direct mating. Whole genomes of three mcr-1-positive Enterobacteriaceae clinical isolates and 11 livestock-origin mcr-1-positive E. coli isolates were sequenced. Results: Two E. coli and one Enterobacter aerogenes clinical isolates carried carried IncI2 plasmids harboring mcr-1, which conferred colistin resistance (E. coli MIC, 4 mg/L; E. aerogenes MIC, 32 mg/L). The strains possessed the complete conjugal machinery except for E. aerogenes harboring a truncated prepilin peptidase. The E. coli plasmid transferred more efficiently to E. coli than to Klebsiella pneumoniae or Enterobacter cloacae recipients. Among the three bacterial hosts, the colistin MIC was the highest for E. coli owing to the higher mcr-1-plasmid copy number and mcr-1 expression levels. Ten mcr-1-positive chicken-origin E. coli strains also possessed mcr-1-harboring IncI2 plasmids closely related to that in the clinical E. aerogenes isolate, and the remaining one porcine-origin E. coli possessed an mcr-1-harboring IncX4 plasmid. Conclusions: mcr-1-harboring IncI2 plasmids were identified in clinical Enterobacteriaceae isolates. These plasmids were closely associated with those in chicken-origin E. coli strains in Korea, supporting the concept of mcr-1 dissemination between humans and livestock.

• Journal of Species Research
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• v.6 no.3
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• pp.207-213
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• 2017

In order to investigate the indigenous prokaryotic species diversity of the Nakdong River system in Korea, fresh water samples from Hapcheonho Lake and Jinyangho Lake were analyzed for bacterial taxonomic diversity. The isolated bacterial strains were identified based on 16S rRNA gene sequences, and those exhibiting at least 98.7% sequence similarity with known bacterial species, but never reported in Korea, were selected as unrecorded species. Eleven unrecorded bacterial species were discovered in this study. The isolates were identified as Aquabacterium citratiphilum, Clostridium ghonii, Curvibacter delicates, Deinococcus depolymerans, Eubacterium moniliforme, Flavobacterium nitrogenifigens, Kineosporia mesophila, Luteibacter jiangsuensis, Microbacterium terricola, Rhizobium larrymoorei, and Sediminicoccus rosea belonging to the phyla Actinobacteria, Bacteroidetes, Firmicutes, Proteobacteria and Deinococcus-Thermus. The selected isolates were further characterized for cellular and colonial morphologies, growth conditions, physiological properties, and enzymatic activities. Descriptive information of these previously unrecorded species is also provided.

• Journal of Species Research
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• v.10 no.2
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• pp.134-141
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• 2021

During a survey of indigenous prokaryotic species diversity of the upstream Nakdong River, South Korea, 12 bacterial strains were isolated for further analysis. These bacterial strains were identified showing at least 98.7% 16S rRNA gene sequence similarity with known bacterial species that were previously unreported in South Korea. The 12 bacterial strains were phylogenetically diverse and assigned to four classes, eight orders, nine families, and ten different genera. The isolates were identified as Leucobacter holotrichiae (99.1%), Leucobacter tardus (99.9%), Rhodococcus rhodochrous (99.9%), Tessaracoccus oleiagri (100%), and Paeniglutamicibacter cryotolerans (99.3%), of the class Actinobacteria; Bacillus coagulans (99.7%) and Bacillus wudalianchiensis (99.1%) of the class Bacilli; Ochrobactrum pseudogrignonense (99.2%) and Paracoccus thiocyanatus (100%) of the class Alphaproteobacteria; and Ideonella azotifigens (99.0%), Polaromonas glacialis(99.3%), and Herbaspirillum seropedicae (99.5%) of the class Betaproteobacteria. The cellular and colonial morphology, biochemical properties, and phylogenetic position of these isolates were examined, and species descriptions are provided.

• Journal of Microbiology
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• v.44 no.4
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• pp.453-456
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• 2006

16 chicken isolates and four clinical isolates of VanB-vanA incongruent vancomycinresistant Enterococcus faecium strains without vanS were isolated in 1999. Pulsed-field gel electrophoresis revealed only a peripheral relationship between the chicken isolates and clinical isolates, but suggested clonal spread in the chicken isolates.

• Journal of Species Research
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• v.12 no.spc2
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• pp.1-6
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• 2023

During an investigation into the indigenous prokaryotic species diversity in Korea, a total of five bacterial strains were isolated from various environments in Korea. The isolated bacterial strains were identified by analyzing their 16S rRNA gene sequences, and those with a minimum of 98.7% sequence similarity with known bacterial species but not reported in Korea were designated as unrecorded species. These isolates were assigned to three phyla, five orders, five families, and five different genera. The isolates were identified as Cumulibacter manganitolerans (99.1%) and Myolicibacterium tusciae (98.7%) of the class Actinomycetes; Bacillus marasmi (99.9%) of the class Bacilli; and Novosphingobium mathurense (100%) and Microvirga ossetica (98.8%) of the class Alphaproteobacteria. Gram reaction, colony and cellular morphology, basic biochemical characteristics, and phylogenetic position of theses isolates are also described.

• Asian-Australasian Journal of Animal Sciences
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• v.14 no.6
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• pp.811-815
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• 2001

The study evaluated different synthetic and semisynthetic media for maximal recovery of rumen bacteria and expression of their antibacterial activity. Rumen Glucose Cellobiose Agar (RGCA) medium was found to be the best for recovery of rumen bacteria. However, L-10 medium was the best for expression of antibacterial activity of ruminal isolates followed by Easy, M-10, RGCA and M-98-5 medium. The present study recommends the use of L-10 medium as the medium of choice for screening of antibacterial activity of ruminal isolates. Comparative evaluation of bacterial counts on different dietary regimes indicated significant difference between different growth media on a specific diet and between diets on specific growth media within a species. However, there is no overall significant difference between total bacterial counts obtained from rumen liquor of cattle and buffalo with respect to either the feeding regime or growth media. Feeding straw based diet to the animal is the best for high recovery of rumen bacteria.