This study investigated viability variation of airborne bacteria in indoor environments. The survival in air as a temporal function of bioaerosol viability was reported for Escherichia coli (KCCM 12119, ATCC 11775). Bacteria suspended in distilled water were aerosolized and entered the vertical duct oriented downward. After measurement of number concentration and colony forming unit (CFU) of the bacteria at different locations of the duct, the viability function was calculated. It was found that the bacteria viability(%) decreased with time after aerosolization, 28.454e^-0.132x (x:time, min). This study demonstrated the potential application of viability function of airborne bacteria to studies of exposure assessment and infection risk analysis.

Antimicrobial resistance and multi-drug resistance patterns have been carried out on total of 210 isolated of Salmonella spp. and pathogenic E. coli isolated from food poisoning patients on January through December 2012 in Incheon, Korea. The highest percentage of antibiotics resistance was found to the following antimicrobial agents: tetracycline 43.8%, ampicillin 34.8%, nalidixic acid 23.8%, sulfamethoxazole/trimethoprim and chloramphenicol 12.4%, and ampicillin/sulbactam 11.4%. The highest percentage of resistance was 37.5% to ampicillin for Salmonella spp. and 59.0% to tetracycline for pathogenic E. coli. Overall the multidrug resistance rates of 1 drug was 26.2%, 2 drugs 9.0%, 3 drugs 9.5%, 4 drugs 7.1%, and 5 or more drugs 12.46%. The multi-drug (MDR) strains to four or more antimicrobial agents among the resistant organisms were quite high: 15.9% and 22.1% for Salmonella spp. and pathogenic E. coli, respectively. The study implies that limitation of unnecessary medication use is pertinent in order to maintaining the efficacy of drugs.

Recently pathogenic E. coli is one of the main foodborne pathogens resulting in many patients in Korea. To understand the characteristics of pathogenic E. coli outbreaks in Korea, the epidemiological investigation reports of pathogenic E. coli outbreak in 2009 (41 reports) and in 2010 (27 reports) were collected in the web site of the Korea Centers for Disease Control and Prevention, reviewed and analysed in this study. The main places of the pathogenic E. coli outbreaks were food catering service area (64.8%) and restaurants (25.0%). The main type of the pathogens were EPEC (44.7%) and ETEC (34.2%). EAEC and EHEC was responsible for 10.5 and 9.2%, respectively. Eight of 68 outbreak cases were caused by more than 2 types of pathogenic E. coli which implicates the complicated contamination pathways of pathogenic E. coli. The incidence rate of pathogenic E. coli was 33.6 ± 30.5% and the main symptoms were diarrhea, stomach ache, nausea, vomiting, and fever etc. The two identified food sources were identified as frozen hamburger pattie and squid-vegetable mixture. To improve the food source identification by epidemiological investigation, food poisoning notification to the agency should not be delayed, whole food items attributed the outbreak should be collected and detection method of the various pathogenic E. coli in food has to be improved. In conclusion, the characteristics between the EHEC outbreaks in the western countries and the EPEC or ETEC outbreaks in Korea needs to be distinguished to prepare food safety management plan. In addition, the development of the trace back system to find the contamination pathway with the improved detection method in food and systemic and cooperative support by the related agencies are necessary.

The objectives of the current study were to evaluate the therapeutic effect of dioctahedral smectite (smectite) against calf diarrhea caused by pathogenic E. coli and/or Salmonella typhimurium. In this study, 20 calves (aged 2~3 months) with diarrhea were used for evaluation of the efficacy of smectite on calf diarrhea with 20% smectite suspension in PBS. Calves received 10 ml smectite suspension three times per day after feeding, and fecal samples were collected at the gate of treatment and on the first, second, third, fourth, and fifth day after administration. On the fifth day after treatment with smectite suspension, the diarrhea index showed a significant decrease in the treated group, compared to the control group (P<0.001). The number of pathogenic E. coli in feces of the treated group was significantly decreased, compared to each control group from the second day after treatment (P<0.001), and that of Salmonella typhimurium was significantly decreased from the first day after treatment (P<0.05). According to the results of the current study, 20% smectite suspension had a therapeutic effect on diarrhea caused by E. coli and/or Salmonella in calves.

Hemorrhagic Escherichia coli (E. coli) is one of the most important agent of diarrhea in piglet. The aim of this study was to investigate the characteristics of virulence genes and genetic diversity in hemorrhagic E. coli isolated from piglets with diarrhea. Among 122 hemorrhagic E. coli, 62 isolates carried single toxin gene like heat-stable toxin (ST), heatlabile toxin (LT), verotoxin 1 (VT1), verotoxin 2 (VT2), spa and eae. The most prevalent toxin gene carried by isolates was ST gene (23 isolates), while the most common association was ST/LT (14 isolates) and ST/LT/VT2 (13 isolates). In pulsed field gel electrophoresis, isolates were not classified as one cluster by epidemiological information including isolated area, isolated year and possessed toxins.

To determine current rate of antimicrobial resistance, a total of 236 isolates from milk samples of dairy cattle with mastitis in Korea during 2010-2011 were examined against 12 antimicrobials using disc diffusion method: 67 Staphylococcus aureus, 74 coagulase-negative Staphylococcus spp. (CNS), and 95 Escherichia coli isolates. The isolates examined in this study were submitted by Local Veterinary Service Laboratories located in 13 provinces and metropolitan cities nationwide. The highest rates of resistance among S. aureus isolates were against ampicillin (56.7%) and penicillin (56.7%), followed by kanamycin (11.9%). All S. aureus isolates were sensitive to lincomycin, amikacin, and cephalothin. Only one isolate showed resistance to tetracycline and oxacillin, respectively. Less than 10% of the S. aureus isolates presented resistance to erythromycin, neomycin, and gentamicin. Among CNS isolates, the most frequently observed resistance was to lincomycin (44.5%), followed by penicillin (28.3%), ampicillin (18.9%), tetracycline (17.5%), kanamycin (13.5%), and erythromycin (9.4%). All or most of the CNS isolates were sensitive to cephalothin, amikacin, neomycin, and gentamicin. The highest rate of resistance among E. coli isolates was against tetracycline (26.3%), followed by streptomycin (21%), neomycin (15%), kanamycin (12.6%), and gentamicin (10.5%). Amikacin was the only antimicrobial to which no E. coli isolates showed resistance. Around 10% of the S. aureus isolates and 15% of the CNS isolates showed resistance against three or more antimicrobials simultaneously, while more than 30% of the E. coli isolates did.

This study was carried out to investigate the antimicrobial resistance pattern and distribution of resistance gene determinants in fecal E. coli from chicken. Antimicrobial susceptibility test was performed on a total of 109 fecal E. coli isolates from chicken, collected in Gyeonggi, Chungbuk, Jeonnam and Jeonbuk province from March to November 2003, by the disk agar diffusion method. Eighteen commonly used antimicrobial agents approved in Korea as veterinary medicine were tested: ampicillin (AM), amoxicillin/clavulanic acid (AMC), cephalothin (CF), cefozolin (CZ), cefoxitin (FOX), cefotaxime (CTX), cefepime (FEP), imipenem (IPM), streptomycin (S), gentamicin (GM), amikacin (AN), ciprofloxacin (CIP), enrofloxacin (ENO), norfloxacin (NOR), trimethoprim/sulfamethoxazole (SXT), erythromycin (E), chloramphenicol (C) and tetracycline (TE). Higher resistance rates (≥50%) were observed against 9 antimicrobial agents including AM, CF, S, CIP, ENO, NOR, SXT, E and TE. Resistance was most frequent for TE in 105 E. coli isolates (96.3%). Twenty-two isolates (20.2%) of the isolates showed multiple antimicrobial resistance to 8, and 19 isolates (17.4%) showed to 7 antimicrobial agents. The distribution of the resistance gene determinants for S and TE was assessed by PCR in resistant isolates. Thirty isolates possessed the strA, strB, and aadA gene, 25 isolates possessed the strA and strB gene among the 66 streptomycin-resistant isolates. Fifty one isolates possessed only the tetA gene, 22 isolates possessed the tetA and tetB gene, 11 isolates possessed only the tetB gene among the tetracycline-resistant isolates.

서울시내에서 유통되는 식품과 식품접객업소(집단급식소 포함)의 조리식품을 대상으로 식중독 원인균 분석 및 위생미생물 검사를 실시한 결과, 분리된 대장균의 항생제 감수성 시험을 통하여 이들의 내성 정도를 파악하고, 내성 유전자와 병원성유전자의 분포도 알아보았다. 모두 1313건 의 샘플 중 50건에서 대장균이 검출되어 3.8%의 검출률을 보였다. 이중 육회 1건에서 장출혈성대장균 O26 1건, 김밥 에서 장병원성대장균 1건이 각각 검출되었다. 50건의 대장 균중 50%가 16종의 항생제에 모두 감수성을 보였으며 내성이 높게 나타난 항생제는 ampicillin(36%), amoxicillin/ clavulanic acid(32%) 그리고 tetracycline(22%)의 순이었다. 이들의 내성유전자 분포는 TEM이 1건, tetB 4건이 각각 검출되었다.

Bacillus thuringiensis 1-3 (Bt 1-3), belonging to subsp. aizawai (H7), showed different characteristics in plasmid profiles from type strain and had cry2A gene in addition to cry1Aa, cry1Ab, cry1C and cry1D. To clone its plasmids and construct E.coli-Bt shuttle vector, we constructed the plasmid capture system (PCS) by inserting attB sites including lacZ between transposable elements (designated as pPCS-Troy). Through in vitro transposition with total plasmids DNA of Bt 1-3, 53 clones were acquired and their sizes were approximately 10 kb. Based on the sequence analysis, they were classified in four groups showing similarities with four known Bt plasmids, pGI3, pBMB175, pGI1 and pGI2, respectively. One of pGI3-like clones, named as pBt1-3, was fully sequenced and its putative open reading frames (ORFs), Rep-protein, double-strand origin of replication (dso), single-strand origin of replication (sso), have been identified. The structure of pBt1-3 showed high similarity with pGI3 which is one of rolling-circle replication (RCR) group VI family. As a donor for construction of shuttle vector, pDonr-attPEm vector harboring erythromycin resistant gene between attP sites was constructed. Through BP recombination with pPCS-Troy-cloned Bt plasmids and pDonr-attPEm, erythromycin resistant gene was transposed to Bt plasmids. This scheme proposes that in vitro transposition using pPCS-Troy and BP recombination using pDonr-attPEm can easily clone Bt plasmids and construct novel shuttle vectors.

The desmutagenic activity of the water extract of Cassia tora L on the mutagenicity induced by 4- nitroquinoline 1-oxide (4-NQO) and N-methyl-N-nitro-N'-nitrosoguani-dine (MNNG) was studied using the SOS Chromotest with Escherichia coli PQ37. The inhibition rates of water extract of Cassia tora L. at concentration of 100 μg/assay were 27.5% and 40% against 4-NQO and MNNG. The water extract of Cassia tora L. was separated into methanol soluble and methanol insoluble parts. The methanol soluble part exhibited higher inhibition effects than the methanol insoluble part against the mutagenic activities of 4-NQO and MNNG. Step-wise fractionation of methanol soluble part was done to obtain methanol, ethyl acetate and water fractions. Among these fractions, water fraction had the strongest inhibitory effects of 23.0 and 19.0% against mutagenicities of MNNG and 4NQO, repectively. The results clearly indicated that the water fraction showed much stronger antimutagenicity against MNNG than 4NQO. The inhibition rates of aqueous fraction of methanol-soluble from water extracted Cassia tora L. at concentrations of 1.0 10, 100 and 250 μg/assay were 8.0%, 12.0%, 25.5% and 43.0%, respectively. The water fraction showed the inhibitory effects with dose response against the mutagenic activities induced by MNNG.

서울시 가락농수산물시장에서 수거한 총 2,066건의 해산물(어류 573건, 패류 721건, 갑각류 208건 그리고 연체류 564건)을 대상으로 대장균을 분리 동정한 결과 10.3%(212/2,066)의 검출율을 보였다. 분리된 212주의 대장균의 월별 분포를 살펴보면, 1월 4.0%, 2월 1.0%, 3월 0.7%, 4월 9.5%, 5월 4.4%, 6월 9.4%, 7월 30.5%, 8월 42.1%, 9월 21.2%, 10월 6.6%, 11월 0.7% 그리고 12월 4.6%의 검출율을 보여, 6-9월 등 하절기에 많은 대장균이 분포됨을 알 수 있었고, 검체별 분포를 살펴보면, 어류가 7.0%(40/573), 패류 12.8%(92/721), 갑각류 8.7%(18/208) 그리고 연체류 11.0%(62/564)의 검출율을 보여, 패류, 연체류가 어류, 갑각류에 비해 대장균 분리율이 비교적 높게 나타났다. 또한, 지역별 분포를 살펴보면, 강원 21.3%의 검출율을 보였고, 인천 15.6%,경남 12.1%, 전남 11.5%, 전북 22.2%, 충남 11.6%, 제주 6.7% 그리고 우리나라 이외의 지역에서 9.0%의 검출율을 보였다. 212주를 대상으로 혈청형 동정을 실시한 결과, O6은 소라, 키조개, 그리고 건해삼에서 각각 1건씩, O25는 문어, 멍게에서 각각 1건씩, O29는 소라, 키조개에서 각각 1건씩, 그리고 O8, O25, O26, O27, O55, O78, O126, O158, O168은 문어, 갈치, 미더덕, 바지락, 낙지, 쭈꾸미, 소라, 오징어 알에서 각각 1건씩, O167도 소라에서 1건 확인되어 총 16주 (7.5% = 16/212)의 O 혈청형이 동정되어 어패류 등 해산물에 대장균이 분포되어 있음을 알 수 있었다.

Carbon Nano Tubes could be either metallic or semi-conducting in nature, depending on their diameter. Its photocatalytic behavior has given an impetus to use it as an anti-microbial agent. More than 95% Escherichia coli and Staphylococcus aureus bacteria got killed when exposed to Carbon Nano Tubes for 30 minutes in presence of sunlight. Carbon Nano Tubes are supposed to have smooth surface on to which it accumulates positive charges when exposed to light. The surface that is non illuminated has negative charge. At the cellular level microorganisms produce negative charges on the cell membrane, Therefore damaging effect of multi walled carbon nano tubes (exposed to light) on the microorganisms is possible. In this paper, photo catalytic killing of microbes by multi walled carbon nano tubes is reported. Killing was due to damage in the cell membrane, as seen in SEM micrographs. Moreover biochemical analysis of membrane as well as total cellular proteins by SDS PAGE showed that there was denaturation of membrane proteins as well as total proteins of both the microbes studied. The killed microbes that showed a decrease in number of protein bands (i.e. due to breaking down of proteins) also showed an increase in level of free amino acids in microbes. This further confirmed that proteins got denatured or broken down into shorter units of amino acids. Increased level of free amino acids was recorded in both the microbes treated with multi walled carbon nano tubes and sunlight.

The antimicrobial activity of metallic nanoparticles against bacteria was investigated. Silver, copper, and titania nanoparticles were tested. The bacteria species E. coli and B. subtilis were selected as models for Gram-negative and Gram-positive bacteria, respectively. Bacteriological tests were performed in Luria-Bertani (LB) medium or Nutrient (NT) medium on solid agar plates containing different concentrations of nanoparticles in the range of 0 to 150 μg/mL. Silver and copper nanoparticles were shown to be an effective bactericide. However, titania nanoparticles were found to be ineffective as an antimicrobial agent. It appears that E. coli cells are more sensitive to the copper nanoparticles than to silver nanoparticles and B. subtilis cells have similar sensitivity against both copper and silver nanoparticles.

본 연구는 시판되는 증자 녹차의 에탄올 추출물과 에탄올 추출물로부터 분획한 분획물로부터 최근 병원성 식중독균으로서 문제시되고 있는 E. coli O157:H7균에 대한 항균성을 검색하였다. 에탄올 추출물로부터 그 유효성분을 조사하기 위하여 핵산, 에틸아세테이트, 클로로포름 및 물로서 분획한 후 MIC를 검색한 결과 에틸아세테이트 분획물이 500μg/disk 농도로 가장 강한 활성을 나타내었으며, 헥산 분획물은 활성이 없었다. 가장 강한 항균력을 나타낸 에틸아세테이트 분획물의 농도별 항균력 및 pH에 대한 영향을 조사한 결과 균종에 따라 차이는 있지만 3균주 모두 250-2000μg/disk 농도에서 새육이 억제되었다. 또한 E. coli O157:H7균은 산성조건에서는 생육이 가능하지만 pH 10 이상의 강한 알칼리 조건에서는 생육이 크게 억제되었다. 35℃에서 E. coli O157:H7 933과 932균에 대한 에틸아세테이트 분획물의 농도별 생육저해 효과를 검색한 결과 두 균주 모두 250μg/ml , 500μg/ml의 농도에서는 12시간 이후부터 생육하기 시작하였으나 1000μg/ml의 농도에서는 생육이 크게 저해되었다.

식품으로부터 다양한 병원 미생물을 신속 검출하기 위하여 다양한 검출 원리를 이용한 키트들이 개발·시판되고 있다. 검사키트는 신속, 정확하고 간단하게 사용할 수 있으므로 검사기관이나 실험실 뿐 아니라 식품회사에서 QC 또는 QA를 수행하기 위하여 사용이 증가되고 있는 추세이다. 이에 본 연구에서 E. coli O157:H7의 단클론항체를 이용하여 면역크로마토그래피법에 의해 개발한 E. coli O157:H7 검출 키트(Donga Co, Korea, D-kit)에 대한 검출감도 및 특이성을 확인하고 식품 시료에 적용 가능성을 평가하였다. 면역크로마토그래피법에 의해 개발?시판되고 있는 Reveal E. coli O157:H7 (Neogen Co., USAm R-kit)와 VIP EHEC kit (Biocontrol INC., USA, V-kit)를 비교 키트로 사용하였다. E. coli O157:H7 표준균주를 사용하여 실시한 검출감도 확인시험 결과 R-kit 및 D-kit는 104/㎖의 농도에서 양성으로 확인되었고 10³/㎖에서도 약한 양성 반응을 보였으나, V-kit는 10?/㎖ 농도로 검출감도가 낮았다. 또한 배양액을 가열하여 kit에 적용하는 것이 가열하지 않은 경우보다 검출감도를 높일 수 있었다. E. coli O157:H7 분리 22주, verotoxin 생성 E. coli 7주 E. coli 분리주 40주 및 38종의 장내세균에 대한 특이성 시험 결과 세 가지 키트 모두에서 동일한 결과를 보였는데, 시험균주 107주 중 3주를 제외한 모든 균에서 음성의 결과를 보여 특이성을 확인하였다. 세 키트에 위양성 반응을 보인 것은 E. coli O157:H19, E. coli O157:H18 및 Salmonella galinarium으로 이들 혈청형과 O157:H7 사이에는 유사한 혈청학적 특성이 존재하는 것으로 추정되었다. 이상의 실험결과로 D-kit는 E. coli O157:H7을 검출하는데 감도 및 특이성 면에서 기존 키트인 R-kit 및 V-kit와 같이 유용한 것으로 확인되었다.

In the 5'-flanking region of the D-AAT, AspAT and AlaDH gene, I found three or two pairs of sequences(designated as P1, P2, P3) which show significant similarity to the E.coli consensus sequences of -35 and -10 for promoters. The spacing between -35 and -10 is 16 to 18bp in all the three putative promoters Pl, P2 and P3 which is in good agreement with the preferred spacer length in E.coli and in B.subtilis. Therefore, the putative promoters may also function to increase the efficiency of transcriptional initiation. The most stable, double-helical $quot;Shine-Dalgarno$quot; pairing is formed with a free energy change(△G) of -13.0 ㎉/㏖, -9.6 ㎉/㏖, -15.8 ㎉/㏖.