• 한국균학회지
• /
• 제51권3호
• /
• pp.179-190
• /
• 2023

Grapevine downy mildew, caused by Plasmopara viticola, significantly damages vineyards and is one of the most devastating diseases affecting cultivated grapes worldwide. In this study, we characterized the phenotypic and molecular traits of 11 P. viticola isolates from four grape-growing regions in South Korea. Additionally, we investigated the diversity of pathogenicity among these isolates and conducted an assay to evaluate the response of grape cultivars to P. viticola infection. Lemon-shaped sporangia were identified in the collected isolates, which released zoospores into the suspension at room temperature. Within a few hours of inoculation, the zoospores developed germ tubes. We tested 11 P. viticola isolates for pathogenicity in 845 grape cultivars to screen for grape host resistance to downy mildew infection. Among the tested isolates, JN-9 showed the highest virulence. Grape cultivars displayed varying phenotypic reactions to P. viticola infection: approximately 7% were highly susceptible, 41% were susceptible, 20% were moderately susceptible, 8% were resistant, and 24% exhibited extreme resistance. Phylogenetic analysis based on four genomic regions (internal transcribed spacer 1 [ITS1], actin, beta-tubulin, and cytochrome c oxidase II) revealed a close evolutionary relationship among all the Korean isolates, forming a single monophyletic lineage. Notably, these isolates showed greater similarity to European isolates than to American isolates. This comprehensive study contributes to a deeper understanding of the identity and behavior of P. viticola, which is crucial for developing effective resistance strategies against this pathogen in grape cultivars cultivated in South Korea.

• Clinical and Experimental Pediatrics
• /
• 제60권7호
• /
• pp.221-226
• /
• 2017

Purpose: Escherichia coli sequence type (ST) 131, a multidrug-resistant clone causing extraintestinal infections, has rapidly become prevalent worldwide. However, the epidemiological and clinical features of pediatric infections are poorly understood. We aimed to explore the characteristics of ST131 Escherichia coli isolated from Korean children with urinary tract infections. Methods: We examined 114 uropathogenic E. coli (UPEC) isolates from children hospitalized at Chung-Ang University Hospital between 2011 and 2014. Bacterial strains were classified into STs by partial sequencing of seven housekeeping genes (adk, fumC, gyrB, icd, mdh, purA, and recA). Clinical characteristics and antimicrobial susceptibility were compared between ST131 and non-ST131 UPEC isolates. Results: Sixteen UPEC isolates (14.0%) were extended-spectrum ${\beta}-lactamase$ (ESBL)-producers; 50.0% of ESBL-producers were ST131 isolates. Of all the isolates tested, 13.2% (15 of 114) were classified as ST131. There were no statistically significant associations between ST131 and age, sex, or clinical characteristics, including fever, white blood cell counts in urine and serum, C-reactive protein, radiologic abnormalities, and clinical outcome. However, ST131 isolates showed significantly lower rates of susceptibility to cefazolin (26.7%), cefotaxime (40.0%), cefepime (40.0%), and ciprofloxacin (53.3%) than non-ST131 isolates (65.7%, 91.9%, 92.9%, and 87.9%, respectively; P<0.001 for all). ESBL was more frequently produced in ST131 (53.3%) than in non-ST131 (8.1%) isolates (P<0.01). Conclusion: ST131 E. coli isolates were prevalent uropathogens in children at a single medical center in Korea between 2011 and 2014. Although ST131 isolates showed higher rates of antimicrobial resistance, clinical presentation and outcomes of patients were similar to those of patients infected with non-ST131 isolates.

• 한국동물위생학회지
• /
• 제40권3호
• /
• pp.193-200
• /
• 2017

This study was carried out to investigate the antimicrobial resistance profiles and resistance genes in 62 Escherichia coli isolated from dogs and cats hospitalized at animal hospitals in Daegu. E. coli isolates showed high resistance to nalidixic acid (46.8%) and ampicillin (45.2%). Resistance to the other antimicrobial agents was less than 30%, and no resistant isolates were detected for imipenem and amikacin. Of the 28 ampicillin-resistant isolates, TEM and CTX-M genes were detected in 16 (57.1%) and 11 (39.3%), respectively. The aadA gene was found in 4 (26.7%) of 15 gentamicin-resistant isolates, and strA-strB gene was found in 10 (66.7%) isolates. The sul I and sul II genes were detected in 11 (61.1%) and 14 (77.8%) of 18 trimethoprim/sulfamethoxazole-resistant isolates, and tetB gene in 9 (81.8%) of 11 minocycline-resistant isolates, and cmlA gene in 2 (22.2%) of 8 chloramphenicol-resistant isolates. The qnrB and qnrS genes were found in 3 (10.3%) and 1 (3.4%) of 28 nalidixic acid-resistant isolates, respectively. Whereas, none of the SHV, CMY-2, tetA, dfr Ia and dfr VII, and qnrA genes were found. Our results show a wide variety of resistance genes in E. coli isolates from dogs and cats. This study also represents the first report of qnrB and qnrS gene producing E. coli isolates from dogs in republic of Korea.

• 한국동물위생학회지
• /
• 제34권3호
• /
• pp.217-226
• /
• 2011

Salmonella spp. is of increasing public health concern as causative pathogens of food poisoning. The aim of this study was to investigate the serotypes and antimicrobial resistance pattern of Salmonella spp. isolated from duck farms in Daegu-Gyeongbuk province. Also, S. Enteritidis and S. Typhimurium isolates were further examined for plasmid analysis, phage typing and pulsed-field gel electrophoresis (PFGE). A total of 34 Salmonella spp. (16.4%) were isolated from duck farms and ten serotypes were identified. The predominant serotypes were S. Typhimurium (23.5%) S. Fyris (17.6%) and S. Haardt (11.8%), S. Agona and S. Enteritidis (respectively 8.8%). Of 34 Salmonella isolates, 15 (44.1%) isolates were resistant to at least one antimicrobial agent and multiple resistance (resistance to more than 4 drugs) was observed in 9 strains (26.5%). The high resistance was found to streptomycin (32.4%), tetracycline (29.4%), ampicillin, kanamycin and nalidixic acid (respectively, 26.5%), all Salmonella isolates were susceptible to cefoxitin, cefotaxime, gentamicin, amikacin and ciprofloxacin. All S. Enteritidis and S. Typhimurium isolates were found to contain only one plasmid (ca. 54 or 55kb, respectively). Among the S. Enteritidis isolates, two phage types were found, PT32a and PT1c, respectively, one isolates did not react with any of the phages used. Whereas, all S. Typhimurium isolates were RDNC (reacts but does not conform). PFGE showed to be a useful typing method better than plasmid analysis and phage typing for discrimination of isolates especially, S. Typhimurium isolates. Our results indicated that the serotypes of Salmonella isolates are widely distributed in duck farms, further epidemiological studies should be carried out.

• 대한미생물학회지
• /
• 제20권1호
• /
• pp.1-11
• /
• 1985

A total of 211 strains of Staphylococcus aureus which included 118 strains isolated from various clinical specimens of admitted patients of University Hospital with systemic or severe cases of infection and 93 strains from infected skin diseases of out-patients of dermatology clinic located in rural area, were tested for the antimicrobial susceptibility to the 12 drugs of common use and the phage typing. An these were subjected to the study of plasmid profile analysis for the molecular epidemiology of nosocomial infections. University Hospital(UH) isolates showed higher frequency of resistance than local clinic(LC) isolates against 10 drugs excluding tetracycline(Tc), and trimethoprim(Tp). The MIC of UH isolates were above than $128{\mu}g/ml$ against 9 drugs except Tc, gentamicin(Gm), and Tp, but LC isolates did not show such a high level of MIC. There was difference of MIC needed to inhibit 90% of strains(MIC90) against each drugs tested between two groups of UH and LC isolates. UH isolates showed 2 to 4 times higher value of MIC90 by two-fold serial dilution of drug concentration than LC isolates. Tp was considered as an effective drug in treatment of staphylococcal infections whereas ampicillin and Gm were appeared to be ineffective. Seventy-three strains(61.9%) of UH isolates and 70(69.9%) of LC were typable with phages from Colindale Reference Laboratory. The prevailing phage type of UH isolates belonged to lytic group II were 27 strains(22.9%) and those of LC isolates belonged to lytic group II were 23 strains(24.7%). Thirteen strains(11.0%) of UH isolates were multiply resistant to more than 5 drugs to 10 drugs but none of LC isolates. Through the lysis method of Kado and Liu followed by agarose gel electrophoresis, none of 211 strains showed plasmid profile. These results were confirmed by re-examination through the method of Birnboim and Doly.

• 한국균학회소식:학술대회논문집
• /
• 한국균학회 2014년도 춘계학술대회 및 임시총회
• /
• pp.21-21
• /
• 2014

A edible mushroom, Hypsizygus marmoreus is commercially cultivated in Northeast Asia. Japan's annual production is 110,000ton or more. Since 2002, cultivation is expanded in Korea. To investigate the morphological, cultural and microscopic characteristics of Hypsizygus marmoreus, 109 isolates were collected from Korea and other countries. Clamp connection, chlamydospore and arthrospore were present in all tested isolates of H. marmoreus except HYM-002 and HYM-004. Also pilealtrama, gilltrama, basidia, basidiospore and cystidia of fruiting body were no difference among the isolates in the present investigation. Morphological characteristics of fruiting body was that color of pileus was brown and white, irregular as marble, the average size 12~22mm and stipes was $46{\sim}91{\times}6{\sim}10mm$. Isolates HYM-031, HYM-047 and HYM-109 formed grayish-brown pileus with a faint pattern. Molecular analysis with RAPD and ITS rDNA sequence analysis were also performed to check the genetic relationships among H. marmoreus isolates. Based on the RAPD analysis using the URP-PCR, all isolates of H. marmoreus were clustered into large 3 groups but more than 90% showed high similarity. In addition, morphological and geographical differences have been classified as an independent cluster. The brown and white strains enclosed in same cluster. So genetically no significance difference was observed between these two strains. ITS gene sequences of 16 selected isolates which were 640 bp long, were aligned and compared. The similarity in ITS sequence was 94.8 to 99.1% among tested isolates and the H. marmoreus isolates in GeneBank. In conclusion the tested isolates were H. marmoreus. Morphological and molecular observations proved that all tested isolates were belonging to H. marmoreus. For the stable artificial cultivation, composition of optimum media, mature period and light condition were established. Optimal formula of artificial cultivation medium was Douglas sawdust: corn cob: soybean meal: wheat bran = 40:30:15:15. In addition, 7% rice bran and 3% yellow sucrose was the most effective composition for spawn's liquid medium. For the maturation of the isolates was favorable for growing for 20 to 30 days at $25^{\circ}C$ and the LED lights in mixture of white and blue was good for growth period. For effective growth, the temperature, humidity and aeration control in every step was important.

• The Plant Pathology Journal
• /
• 제17권5호
• /
• pp.276-280
• /
• 2001

Fusarium isolates of Gibberella fujikuroi species complex were obtained from sorghum grown in five provinces of Korea in 1996 and 1997. These isolates were characterized based on their mating behavior, mycotoxin production, and vegetative compatibility. Only three mating populations (A, D, and F) were recovered from a total of 155 isolates examined. The relative frequency of the mating populations was significantly different: F was predominant (80%), while D and A were observed at low frequencies of 9% and 3%, respectively. Female fertile isolates were more common within F (44 our of 124) than D (2 out of 14), while none of the five A isolates were female fertile. The inbreeding effective population sizes ($\textrm{N}_e$)for mating type and male/hermaphrodite ratios in mating populations A and D produced significant amounts of fumonisins, while F isolates produced none or only traces of fumonisin B$_1$. In contrast. F isolates produced higher amounts of moniliformin (average of 3,820 ppm) than A and D isolates (averages of 77 and 1,819 ppm, respectively). Fifty-one isolates were tested for vegetative compatibility using nitrogen non-utilization mutants of each isolate, and 44 vegetative compatibility groups (VCGs) were identified. A single VC type (VC1) was found in all of the five A isolates examined. Six of the D isolates examined consisted of three VC types: two for VC2, two for VC3, and the rest for VC4. All of the F isolates tested were incompatible in every combination and , thus, each constituted a unique VCG.

• Mycobiology
• /
• 제32권1호
• /
• pp.17-23
• /
• 2004

Growth of ten isolates of Catenaria anguillulae on linseed oil-cake agar medium was studied at 10, 13, 15, 20, 25, 30, 35, 40, 44 and $46^{\circ}C$. The cardinal temperatures of these isolates were also determined. Observations clearly revealed that the isolates differed in their temperature requirements. Isolate GA was found to grow best at $40^{\circ}C$, whereas VF isolate showed best growth at 35 and $40^{\circ}C$. Isolates PA, KA, CHP, KO, MA and SWP grew best at $35^{\circ}C$. The other isolates(KP and MMT) showed their best growth at $30^{\circ}C$. Based on radial growth, isolates were categorized as fast growing, medium growing and slow growing. Studies on effect of different temperatures on pathogenicity was made using only three isolates: VF, KP and MA against Xiphinema basin. VF isolate caused maximum infection at $40^{\circ}C$, whereas KP and MA isolates caused maximum infection at $30^{\circ}C$. The morphology of sporangia varied with temperature in isolates producing elongate-elliptical or filamentous sporangia. In VF isolate the sporangia were largely iilamentous to elongate elliptical at $30^{\circ}C$. The width of the sporangia increased with increasing and decreasing temperatures. At $44^{\circ}C$ the sporangia of this isolate were mostly broadly elliptical or spherical. This clearly indicates that sporangia vary in morphology with temperature. From the morphometrical studies it was understood that sporangial morphology was more consistent and reliable for grouping of isolates. Based on the morphology of sporangia the isolates of C. anguillulae were characterized in three groups viz., Mamentouslelongate elliptical(VF, KA, GA and SWP), spherical(PA, KP, MA and MMT) and vertically elongate sporangia(CHP and KO).

• International Journal of Industrial Entomology and Biomaterials
• /
• 제31권2호
• /
• pp.107-114
• /
• 2015

Endophytes provide multifarious benefits such as promotion of plant growth and yield, suppression of phyto-pathogens, phosphate solubilising and fixation nitrogen. A study has been carried out to explore growth promotion and antifungal activities of endophytes of mulberry (Morus spp.). Endophytic bacteria were isolated from mulberry plants and studied their cultural, morphological characters, growth promotion as well as their antifungal activity against Rhizoctonia bataticola and Fusarium oxysporum , two mulberry root rot associated pathogens. Except two isolates, all bacteria were colourless and the colony size of eight isolates was small. The margin of five isolates was irregular and the consistency of three isolates was creamy, six isolates was slimy and one was mucoid. Texture of seven isolates was convex and others were flat. Eight isolates were gram positive and the rest Gram negative, five were cocci and others were bacilli (rod shaped). Four isolates were motile and all were catalase positive and only three isolates were oxidase positive. Spore staining was positive only for two isolates. The growth promotion study showed that there was significant difference in root length and seedling length. The antagonistic effect of the bacterial isolates was tested against R. bataticola showed significant (p <0.05) influence of the bacteria, days after inoculation and their interaction on the inhibition of fungal growth. The isolate En-7 completely inhibited the fungus followed by En-5 (66.67%). The bacterial isolates significantly (p <0.05) inhibited growth of F. oxysporum in PDA. The mean inhibition was higher (70.45%) in case of En-7 followed by En-8 (68.65%) and En-10 (66.44%). The study reveals that some endophytic bacteria associated with mulberry have growth promotion and antifungal activity and could be explored for promotion of mulberry growth and managing root rot disease.

• Journal of Microbiology and Biotechnology
• /
• 제27권11호
• /
• pp.2052-2059
• /
• 2017

The emergence and dissemination of Salmonella genomic island 1 (SGI1) are strongly associated with the occurrence of multidrug-resistant (MDR) enterobacteria in humans and animals. Diverse SGI1s have been reported among Salmonella enterica and Proteus mirabilis in several countries. We aimed to characterize SGI1 in P. mirabilis isolates from humans and chickens in Chungcheong Province, Korea. A total of 44 P. mirabilis isolates were recovered from humans (n = 20) and chickens (n = 24). Antimicrobial susceptibility was determined by disk diffusion assay. To detect and characterize SGI1s, PCR amplification and PCR mapping experiments were performed. Repetitive extragenic palindromic-PCR (REP-PCR) was performed to assess the clonality of the isolates. The four P. mirabilis strains (16.7%) from chicken harbored a SGI1, whereas none of the isolates from clinical specimens contained SGI1. The SGI1s detected in our study were all confirmed as SGI1-PmABB harboring aminoglycoside-resistant genes (aacCA5 and aadA7). In P. mirabilis isolates, the presence of SGI1-PmABB was significantly correlated with high resistance rates of the isolates to antimicrobial agents, such as gentamicin, streptomycin, and spectinomycin. Moreover, the four SGI1-bearing isolates showed the same REP-PCR patterns and that suggested both horizontal and clonal spread of the isolates. This study is the first attempt to determine SGI1s in P. mirabilis isolates in Korea. We confirmed that P. mirabilis isolates carrying SGI1-PmABB were distributed at poultry farms in Korea. The present study emphasizes the need for continuous monitoring of SGI1s to prevent spreading of the MDR genomic islands among P. mirabilis isolates from humans and animals.