• 생태와환경
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• 제50권1호
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• pp.137-147
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• 2017

독소 생성 분류군의 정의는 분리균주에 의해서 동정되고, 단일배양에 의한 독소 생성 여부 및 유전적 검토가 확인된 분류군을 의미한다. 이러한 관점에서 Aphanizomenon flos-aquae의 독소 생성능은 세계적으로 아직 논쟁의 여지가 있다. 본 연구는 낙동강에서 분리한 Aphanizomenon flos-aquae (DGUC001, DGUC003)을 대상으로 16S rRNA 염기서열을 이용하여 계통학적 위치를 확인하고, 남세균독소인 saxitoxin (STX)과 cylindrospermopsin (CYN)의 잠재적 생성능력을 유전자 수준에서 검토하였다. 연구에 사용된 균주는 2016년 8월과 2016년 10월에 낙동강 본류구간의 하천수에서 분리되었다. 계통학적 분석에는 16S rRNA가 사용되었으며, 독소 생성 유전자는 CYN과 STX 생합성에 관여하는 cyrA, cyrJ, sxtA, sxtI 유전자가 선택되었다. 분리된 균주 DGUC001과 DGUC003은 육안으로 관찰 가능한 크기의 다발(fascicles)을 형성하였으며, 세포사(trichome)가 병렬 형태로 나열되고, 세포사의 양쪽 끝에 위치한 말단 세포(terminal cell)가 거의 투명하거나 긴 끈 형태의 세포질을 가지고 있었다. 또한, 두 개의 균주는 98.4%의 유전적 유사도를 나타내어 동일종으로 판단되었고, 유전자 은행에서 선별한 Cluster I의 Aph. flos-aquae strains과도 계통수에서 66~82%의 bootstrap value의 지지도로 단일 cluster에 포함되었다. 확보된 두 개 균주의 유전자 정보는 유전자은행 NCBI에 등록되었으며, KY327795, KY327796의 Accession no.를 부여받았다. 한편, 세포독소 CYN의 생합성에 관여하는 유전자 cyrA와 cyrJ는 두 개 균주 모두에서 확인되지 않았다. STX의 생합성을 담당하는 유전자 중 sxtA 유전자는 두 개의 균주에서 확보되었으며, 독소생합성 과정의 분자생물학적 지표 역할을 하는 sxtI 유전자는 발견되지 않았다. 따라서 낙동강 현장시료에서 분리된 두 개의 균주는 형태학적 및 계통분류학적으로 동일종인 Aphanizomenon flos-aquae Ralfs ex Bornet et Flahault 1888로 동정되었으며, 두 개의 균주는 CYN과 STX의 잠재적인 독소 비생성 균주로 확인되었다. 이 결과를 통하여 Aph. flos-aquae가 독소 생성 분류군으로 분류되는 것에 대한 보다 면밀한 검토가 필요할 것으로 판단되었다.

• Molecules and Cells
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• 제42권4호
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• pp.333-344
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• 2019

Various genetic and environmental factors are known to be associated with chronic obstructive pulmonary disease (COPD). We identified COPD-related differentially expressed genes (DEGs) using 189 samples accompanying either adenocarcinoma (AC) or squamous cell carcinoma (SC), comprising 91 normal and 98 COPD samples. DEGs were obtained from the intersection of two DEG sets separately identified for AC and SC to exclude the influence of different cancer backgrounds co-occurring with COPD. We also measured patient samples named group 'I', which were unable to be determined as normal or COPD based on alterations in gene expression. The Gene Ontology (GO) analysis revealed significant alterations in the expression of genes categorized with the 'cell adhesion', 'inflammatory response', and 'mitochondrial functions', i.e., well-known functions related to COPD, in samples from patients with COPD. Multi-omics data were subsequently integrated to decipher the upstream regulatory changes linked to the gene expression alterations in COPD. COPD-associated expression quantitative trait loci (eQTLs) were located at the upstream regulatory regions of 96 DEGs. Additionally, 45 previously identified COPD-related miRNAs were predicted to target 66 of the DEGs. The eQTLs and miRNAs might affect the expression of 'respiratory electron transport chain' genes and 'cell proliferation' genes, respectively, while both eQTLs and miRNAs might affect the expression of 'apoptosis' genes. We think that our present study will contribute to our understanding of the molecular etiology of COPD accompanying lung cancer.

• Journal of Veterinary Science
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• 제23권1호
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• pp.9.1-9.11
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• 2022

Background: Escherichia coli, which causes subclinical or clinical mastitis in cattle, is responsible for transmitting antimicrobial resistance via human consumption of raw milk or raw milk products. Objectives: The objective of this study was to investigate the molecular characteristics of 183 E. coli from bulk tank milk of five different dairy factories in Korea. Methods: The molecular characteristics of E. coli such as serogroup, virulence, antimicrobial resistance, and integron genes were detected using polymerase chain reaction and antimicrobial susceptibility were tested using the disk diffusion test. Results: In the distribution of phylogenetic groups, group D was the most prevalent (59.6%) and followed by group B1 (25.1%). The most predominant serogroup was O173 (15.3%), and a total of 46 different serotypes were detected. The virulence gene found most often was fimH (73.2%), and stx1, fimH, incC, fyuA, and iutA genes were significantly higher in isolates of phylogenetic group B1 compared to phylogenetic groups A, B2, and D (p < 0.05). Among 64 E. coli isolates that showed resistance to at least one antimicrobial, the highest resistance rate was observed for tetracyclines (37.5%). All 18 integron-positive E. coli carried the integron class I (int1) gene, and three different gene cassette arrangements, dfrA12+aadA2 (2 isolates), aac(6')-Ib3+aac(6')-Ib-cr+aadA4 (2 isolates), and dfrA17+aadA5 (1 isolate) were detected. Conclusions: These data suggest that the E. coli from bulk tank milk can be an indicator for dissemination of antimicrobial resistance and virulence factors via cross-contamination.

• 한국동물위생학회지
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• 제46권1호
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• pp.35-45
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• 2023

Pathogenic Escherichia coli is the cause of a wide range of diseases in pigs, including diarrhea, edema disease, and septicemia. Diarrhea caused E. coli may result in significant economic losses, making pathogenic E. coli an important pathogen for the swine industry. This study investigated the prevalence of virulence factor genes, antimicrobial resistance phenotypes, and resistance genes in E. coli isolated from feces of piglets in Korea between 2017 and 2020. As a result, 119 pathogenic E. coli isolates were obtained from 601 fecal samples. The F4 adhesin gene and the STb enterotoxin gene were commonly present in E. coli isolated from diarrhea samples. The dominant virulotypes of isolates from diarrhea samples were STb, Stx2e, and F4:LT:STb. More than 80% of the screened isolates were resistant to ampicillin, sulfisoxazole, chloramphenicol, or tetracycline. To confirm the resistance mechanisms for β-lactam or quinolone, we investigated the genotypic factors of resistance. Each of the ceftiofur-resistant E. coli produced an extended-spectrum β-lactamase encoded by bla_CTX-M-14, bla_CTX-M-27, and bla_CTX-M-55. And all ciprofloxacin-resistant E. coli harbored mutations in quinoloneresistance-determining-regions. In addition, some of the ciprofloxacin-resistant E. coli contained the plasmid-mediated-quinolone-resistance genes such as qepA, qnrB1, or qnrD. This study has confirmed that the F4 fimbria and the STb enterotoxin are the most predominant in pathogenic E. coli isolated from piglets with diarrhea in Korea and there is a great need for responsible and prudent use of antimicrobials to treat colibacillosis.

• 대한수의학회지
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• 제37권3호
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• pp.541-546
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• 1997

VT2(Verotoxin-2)의 효소활성 영역에 해당되는 두 영역의 아미노산들에 대하여, 첫번째 보존영역의 Glu167을 conservative point mutation 시키고, 두 번째 보존영역의 구성 아미노산 5개 전부를 deletion mutation 시켜, 각 변이주에서 독성의 감소 정도를 wild type과 비교한 결과 다음과 같은 성적을 얻었다. 1. pKSC101을 Eco RI과 Pst I으로 절단하여 940bp insert를 통일 제한효소로 절단한 M 13mp19에 삽입하여 pEP19RF를 구축하였다. 이를 이용하여 dU-SSDNA template를 제조하고, mutagenic primer를 annealing 하여 변이를 도입하였으며, 변이가 도입된 insert를 acceptor plasmid에 삽입시켜 각각 발현 플라스미드 pOEX와 pDEX를 구축하였다. 각각의 mutant 단백질을 발현시키기 위하여 pOEX와 pDEX를 JM109에 형질전환시켜 mutant 재조합 균주인 POMUT109와 DEMUT109를 작성하였다. 2. POMUT109와 DEMUT109를 IPTG 유도 발현시킨 배양상층액을 Vero cell에 대하여 세포독성을 시험한 결과 wild type에 비하여 POMUT109의 배양 여액에서는 2000배, DEMUT109의 배양여액에서는 적어도 3000배 이상의 세포독성을 감소시켰다.

• Journal of Microbiology and Biotechnology
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• 제19권5호
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• pp.525-529
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• 2009

Cytolethal distending toxins (CDTs) represent an emerging family of newly described bacterial products that are produced by a number of pathogens. The genes encoding these toxins have been identified as a cluster of three adjacent genes, cdtA, cdtB, and cdtC, plus 5 cdt genetic variants, designated as cdt-I, cdt-II, cdt-III, cdt-IV, and cdt-V, have been identified to date. In this study, a general multiplex PCR system designed to detect Escherichia coli cdts was applied to investigate the presence of cdt genes among isolates. As a result, among 366 E. coli strains, 2.7% were found to carry the cdtB gene. In addition, the use of type-specific primers revealed the presence of cdt-I, cdtIV, and cdt-V types of the cdt gene, yet no cdt-II or cdt-III strains. The presence of other virulence genes (stxl, stx2, eae, bfp, espA, espB, and espD) was also investigated using a PCR assay. Among the 10 cdtB gene-positive strains, 8 were identified as COT-producing typical enteropathogenic E. coli (EPEC) strains ($eae^+$, $bfp^+$), whereas 2 were identified as CDT-producing atypical EPEC strains ($eae^+$, $bfp^-$). When comparing the cytotoxic activity of the CDT-producing typical and atypical EPEC strains, the CDT-producing atypical EPEC strains appeared to be less toxic than the CDT-producing typical EPEC strains.

• 대한수의학회지
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• 제46권4호
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• pp.337-345
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• 2006

The shigellae are common etiological agents of bacillary dysentery in humans and primates. During four years from 2002 to 2005, 22 strains of Shigella spp. were isolated from the diarrheic patients in Seoul region. All of them were identified as S. flexneri by biochemical tests and serotyping. The prevalence of serotypes were variable by year, but the major serotypes were 2a and 3a. In an antimicrobial susceptibility test, all of the isolates were resistant to streptomycin and tetracycline, and susceptible to amikacin, kanamycin, cefoxitin, and gentamicin. All of the isolates showed the multi-resistant patterns over 3 drugs. By analysis of the plasmid profile the isolates were classified into 7 groups (P1~P7). Serotypes 2a and 2b were distributed to P1, P2, P3, and P4. Serotype 3a was differentiated to P5 and serotype 3b, to P6 and serotype 4a, to P7. PCR results showed that all isolates were positive for two virulence genes, ipaH and ial, but none of the strains had stx gene. The set1A and set1B genes were detected from 12 isolates (54.5%) that belonged to serotype 2a and 2b. The sen gene was detected from 19 isolates (86.4%). The 22 isolates showed 12 to 17 DNA fragments in the sizes ranging from 20.5 kb to 1135 kb, resulting in 13 patterns by the PFGE with Not I digestion. The PFGE patterns of the isolates showed the close relation with the serotypes, but no relations with year of isolation and antimicrobial resistance.

• 한국식품위생안전성학회지
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• 제35권3호
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• pp.271-278
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• 2020

Enterotoxigenic Escherichia coli는 신생 및 이유기 돼지설사의 주요 원인체로서 전세계적으로 양돈산업에 큰 경제적 손실을 끼치고 있다. 그러나 현재 국내에는 이러한 E. coli가 보유하는 다양한 병원성유전자의 분포 및 특성에 대한 정보가 부족한 실정이다. 이에 본 연구에서는 2013년부터 2016년까지 국내 163개 양돈농장에서 이유기 설사증 개체로부터 면봉스왑 샘플을 채취하여 동일 농장의 개체일 경우 5개에서 10개 정도를 혼합한 후, MacConkey agar에 배양하여 최종 API 32E system을 통하여 동정하였다. 분리된 모든 균주에 대해서 3 가지의 다른 multiplex PCR을 수행하여 총 13 종의 병원성유전자의 분포를 확인하였다. 이를 통하여 총 172개의 최소 한가지 이상의 병원성 유전자를 가지는 E. coli 균주를 확인하였고, 그 결과 병원성 유전자의 분포는 (1) fimbrial adhesins (43.0%): F4 (16.9%), F5 (4.1%), F6 (1.7%), F18 (21.5%), and F41 (3.5%); (2) toxins (90.1%): LT (19.2%), STa (20.9%), STb (25.6%), Stx2e (15.1%), EAST1 (48.3%); and (3) non-fimbrial adhesin (19.6%): EAE (14.0%), AIDA-1 (11.6%) and PAA (8.7%)로 나타났다. 결론적으로 본 연구결과는 국내 양돈농장의 이유기 설사증에 관연하는 E. coli는 다양한 종류의 병원성 유전자를 가지고 있으며 그러한 병원성 유전자의 조합도 매우 다양하게 분포하고 있음을 나타낸다.