마이코플라즈마 하이오뉴모니애 박테린 백신 효능의 미생물학적, 면역학적, 병리학적 평가

학위논문(박사) -- 서울대학교대학원 : 수의과대학 수의학과, 2023. 2. 채찬희.Mycoplasma hyopneumoniae는 돼지에서 일차적으로는 유행성 폐렴(enzootic pneumonia)을 일으키는 병원체이며, 감염 시 호흡기도 상피세포와 섬모를 파괴하여 2차적인 세균이나 바이러스 감염을 유발하므로 돼지호흡기복합감염증(PRDC, Porcine Respiratory Disease Complex)의 병인학에서 매우 중요한 위치를 차지한다. 양돈 산업에 있어서 M. hyopneumoniae는 전 세계적으로 유병률이 높고, 성장 정체 및 사료 효율 저하를 유발하여 농가에 심각한 경제적 손실을 주고 있다. 지금까지 M. hyopneumoniae를 통제하고 예방하기 위한 여러 노력이 있었으나 수 킬로미터에 걸친 공기 전파가 가능한 병원체의 특성과 양돈 농가의 밀집 사육 관행으로 인하여 M. hyopneumoniae의 박멸 및 청정상태의 유지는 매우 어렵다. 따라서 백신 접종이 M. hyopneumoniae 감염을 통제할 수 있는 가장 효율적인 수단으로 간주된다. 본 연구의 목적은 새로운 돼지 M. hyopneumoniae bacterin 백신의 한국 도입을 위해 실험적으로 유도한 M. hyopneumoniae 감염 모델과 국내 야외 환경에서 백신의 효능과 안전성을 임상학적, 미생물학적, 면역학적, 병리학적 기법으로 분석하는 것이다. 백신의 효능은 M. hyopneumoniae의 비강 배출을 통해 미생물학적으로 평가하였으며, 또한 면역학적으로는 ELISA와 인터페론 감마 분비세포(IFN-γ-SC) 수의 측정을 통해 체액성 면역 및 세포 매개성 면역 효능을 평가하였다. 폐의 육안병변과 조직병변을 점수화하여 병리학적 평가를 하였다. 백신의 안전성은 호흡기 질환에 대한 임상적인 평가와 일당 증체율을 지표로 평가하였다. 첫 번째 실험에서는 실험실 조건에서 국내 병원성 M. hyopneumoniae 분리주를 사용한 감염 모델에서 백신의 효능을 평가하였다. 실험 결과, 백신을 접종한 그룹은 접종하지 않은 그룹에 비해 M. hyopneumoniae 특이적인 ELISA 항체와 IFN-γ-SC를 유의적으로 더 많이 유도하였다. M. hyopneumoniae의 비강 배출과 폐 병변 분석에서도 백신을 접종한 그룹이 그렇지 않은 그룹에 비해 유의적으로 낮은 수준을 나타내었다. 따라서 평가된 백신은 국내 병원성 M. hyopneumoniae 분리주의 감염 컨트롤에도 효과적인 것으로 판단되었다. 두 번째 실험에서는 돼지 유행성 폐렴 진단 이력이 있는 국내 양돈 농장 3개소에서 백신의 효능과 안전성을 평가하였다. 실험 결과, 3개 농장 모두 백신을 접종한 그룹은 접종하지 않은 그룹에 비해 호흡기 임상 증상이 유의하게 낮았으며, 증체율은 유의하게 높았다. 또한 3개 농장 모두 백신을 접종한 그룹에서 백신을 접종하지 않은 그룹에 비해 M. hyopneumoniae 특이적인 IFN-γ-SC가 유의적으로 더 많이 유도되었으며, 폐 병변의 중증도는 유의하게 낮았다. 따라서 평가된 백신이 M. hyopneumoniae 병원체가 상재한 환경에서 세포 매개 면역을 효과적으로 유도하고, 폐 병변의 중증도와 호흡기 임상 증상을 완화시켜 증체율을 효과적으로 향상시켰음을 확인할 수 있었다. 두 가지 실험에서 새로운 돼지 M. hyopneumoniae bacterin 백신을 임상학적, 미생물학적, 면역학적, 병리학적 기법으로 평가하였으며, 그 결과 국내 병원성 분리주에 대해서도 효과적인 방어능을 확인하였고, 야외 환경에서 적용하였을 때 개선된 증체율을 확인할 수 있었다. 새로운 돼지 M. hyopneumoniae bacterin 백신은 M. hyopneumoniae 감염을 통제할 수 있는 또 하나의 선택지를 제공할 수 있으며, M. hyopneumoniae가 돼지호흡기복합감염증에서 1차 병원체의 역할을 하고, 양돈 농가에 심각한 경제적 타격을 주는 점을 고려할 때 이는 동물복지와 양돈 산업의 지속적인 성장에 매우 중요한 시사점을 준다.Mycoplasma hyopneumoniae is the primary pathogenic agent of enzootic pneumonia in pigs, and it becomes very important in the etiology of the porcine respiratory disease complex (PRDC) as it gives damage to the ciliated epithelium of the trachea, bronchi, and bronchioles so makes pig susceptible to secondary bacterial and viral invaders. In the pig industry, M. hyopneumoniae is a high prevalent worldwide, causes significant economic losses to farms resulting from growth retardation and poor feed efficiency. Although there have been many efforts to control and prevent M. hyopneumoniae, it is very difficult to eradicate and maintain M. hyopneumoniae free due to the nature of airborne pathogens can spread several kilometers and the dense breeding practices of pig farms. Therefore, vaccination is considered the most efficient tool of controlling M. hyopneumoniae. The purpose of this study is to analyze the efficacy and safety of the new single-dose inactivated M. hyopneumoniae bacterin in Korean field and laboratory condition using a clinical, microbiological, immunological, and pathological technique. The efficacy of the vaccine was evaluated microbiologically through the nasal shedding of M. hyopneumoniae and was assessed humoral and cell-mediated immunity through enzyme-linked immunosorbent assay (ELISA) and measuring the number of interferon gamma secreting cells (IFN-γ-SC) in peripheral blood mononuclear cells (PBMC). Pathological evaluation was performed by the observation of gross and microscopic in lung lesion, and the isolation of M. hyopneumoniae antigen in the lesion. The safety of the vaccine was evaluated as an index for clinical evaluation of respiratory diseases and average of daily weight gain (ADWG). Chapter I is with the efficacy evaluation of the vaccine under laboratory condition using challenge model of Korean pathogenic M. hyopneumoniae isolate. As a result of the experiment, the vaccinated group significantly induced more M. hyopneumoniae-specific ELISA antibodies and IFN-γ-SC in PBMC compared to the unvaccinated. The nasal shedding and lung lesion analysis of M. hyopneumoniae also showed significantly lower levels in the vaccinated group than the unvaccinated. Therefore, the vaccine is considered to be effective in controlling infection of Korean pathogenic M. hyopneumoniae isolates. Chapter II is with the evaluation of efficacy and safety of the vaccine at three commercial pig farms with a history of swine enzootic pneumonia in Korea. As a result of the experiment, the vaccinated groups in all three farms had significantly lower respiratory clinical symptom, and the higher average of daily weight gain than the unvaccinated groups. Furthermore, in all three farms, the vaccinated group significantly induced more M. hyopneumoniae-specific IFN-γ-SC than the unvaccinated group. The severity of lung lesions of the vaccinated groups was significantly lower than that of the unvaccinated groups. Therefore, it was confirmed that the vaccine effectively induced cell-mediated immunity in the environment in which the M. hyopneumoniae pathogen is present, and effectively improved the daily weight gain by alleviating the severity of lung lesions and respiratory clinical symptoms. Above two series studies, the new single-dose inactivated M. hyopneumoniae bacterin was assessed for clinical, microbiological, immunological, and pathological parameters. The vaccine demonstrated the protection ability against challenging domestic pathogenic isolates, and the improved daily weight gain was confirmed when applied in field condition. The new single-dose inactivated M. hyopneumoniae whole-cell bacterin can provide another option to control M. hyopneumoniae and considering that it is the primary agent for the Porcine Respiratory Disease Complex and causing a severe economic impact to swine farmers, this can suggest an important implication to sustainable growth in animal welfare and the swine production industry.GENERAL INTRODUCTION 1 LITERATURE REVIEW – Mycoplasma hyopneumoniae 3 1. Introduction 3 2. Etiology 5 3. Pathogenesis 7 4. Swine enzootic pneumonia 10 5. Porcine respiratory disease complex 12 6. Epidemiology 14 7. Immunity 18 8. Vaccine 21 9. References 27 CHAPTER I. Experimental evaluation of Mycoplasma hyopneumoniae bacterin against a Korean M. hyopneumoniae challenge 48 1. Abstract 49 2. Introduction 50 3. Materials and Methods 51 4. Results 56 5. Discussion 63 6. References 65 CHAPTER II. Field evaluation of a new single-dose Mycoplasma hyopneumoniae bacterin effects on growth performance 69 1. Abstract 70 2. Introduction 71 3. Methods 72 4. Results 79 5. Discussion 91 6. References 95 GENERAL CONCLUSION 101 ABSTRACT IN KOREAN 104박

시장경제와 중소규모협동조합의 역할분석 및 정책 제언

이 글은 저작권자의 승락을 얻어 단행본 『한국형 시장 경제체제』(2014년, 이영훈 편, 서울대학교출판문화원)의 제10장을 저자가 요약 발췌하여 작성되었다.협동조합은 개도국은 물론 선진국에서도 고용제공 및 유지, 공정한 부의 재분배 실현 등 사회 및 경제의 지속적 발전에 중요한 조직형태이다. 전 세계적으로 10억명 이상이 조합원이며, 전 세계 인구의 절반이상인 30억 명 이상이 협동조합(기업)의 영향을 받고 있는 것으로 추정된다. 특히, 08년 세계경제 위기 시 유럽에서 협동조합들의 효과적 대응이 확인됨에 따라 전 세계적으로 협동조합의 잠재적 가능성에 대해 재인식하고 있다. 08년 금융위기에 따른 대량해고가 월가를 덮쳤을 때 이탈리아 경우 같은 시기 8,000개 협동조합에서 단 1명도 해고하지 않았다. 우리의 경우도 고용창출을 기대하면서 제정·시행된 협동조합기본법에 근거한 협동조합이 법 시행 1년 여 만인 지난 10월 말 현재 2,851개가 설립되어 협동조합에 대한 시장의 기대가 매우 큼을 알 수 있다. 이에 따라 선진국의 선행연구고찰을 통하여 경제발전과정에서 협동조합의 역할을 알아보고, 현재 우리나라 협동조합 및 관련정책의 문제점을 살펴보고 향후 협동조합의 정책방향에 대하여 제언하고자 한다

Development of Case Database and Conceptual Structural Design Method using Case-Based Reasoning for Tall Buildings

Conceptual structural design of tall buildings consists of selecting structural materials and form of a building and producing a preliminary dimensional layout. Key parameters of a building, such as height of the building, typical live load, wind velocity, design acceleration, maximum lateral deflection, span, and story height, are important factors in the conceptual design phase. Knowledge solutions from similar problems in the past can be used for defining and finding a solution to a design problem. CBR(Case-based reasoning) is a problem solving approach that uses past experience and is highly useful to finding solutions for similar problems. In this paper, the conceptual structural design method using CBR which is intended to assist engineers in the schematic phase of the structural design of tall buildings is introduced. Inductive retrieval method and nearest-neighbor retrieval method are used for selecting structural system and similar design case, respectively. This study presents a schematic design method based on CBR using design information of tall building as a solution for the preliminary conceptual design stage.1. 서론 = 1 1.1 연구의 배경 및 목적 = 1 1.2 연구 동향 = 3 1.3 연구범위 및 방법 = 4 2. 사례기반추론기법 = 7 2.1 사례기반추론의 개요 = 7 2.2 사례 기반 추론(Case-BasedReasoning)의 특징 = 8 2.2.1 사례기반추론의 장·단점 = 9 2.2.2 사례 기반 추론과 규칙 기반 추론(다른 인공지능기법)의 차이 = 9 2.3 사례 기반 추론(Case-BasedReasoning)의 절차 = 11 2.3.1 사례의 표현 = 11 2.3.2 사례의 색인 및 검색 = 12 2.3.3 사례의 조회 = 14 2.3.4 사례적응(caseadaptation) = 17 3. 사례기반추론기법을 이용한 개념구조설계법 = 19 3.1 초고층 건물 구조시스템의 분류 = 19 3.2 국내 초고층건물의 사례분석 = 22 3.2.1 국내초고층건물의 구조적 특성 = 22 3.2.2 국내초고층건물의 현황 = 23 3.2.3 웹기반 사례 데이터(Case Data) 구축 = 32 3.4 귀납적 조회기법 = 33 3.4.1 해안 지역의 알고리즘 개발 = 33 3.4.2 내륙 지역의 알고리즘 개발 = 39 3.5 최근린 조회기법 = 46 3.5.1 가중치에 따른 결과값의 비교 = 47 3.5.2 가중치에 따른 유사도의 비교 = 49 4. 초고층 건물 적용예제 = 53 4.1 귀납적 조회기법을 이용한 구조시스템 선정 = 53 4.2 최근린 조회기법을 이용한 유사설계 사례도출 = 57 5. 결론 = 60 참고문헌 = 6

Trendelenburg position with hip flexion as a rescue strategy to increase spinal anaesthetic level after spinal block

BACKGROUND: When the level achieved by a spinal anaesthetic is too low to perform surgery, patients are usually placed in the Trendelenburg position. However, cephalad spread of the hyperbaric spinal anaesthetics may be limited by the lumbar lordosis. The Trendelenburg position with the lumbar lordosis flattened by hip flexion was evaluated as a method to extend the analgesic level after the administration of hyperbaric local anaesthetic. METHODS: When the pinprick block level was lower than T10 5 min after intrathecal injection of hyperbaric bupivacaine (13 mg), patients were recruited to the study and randomly allocated to one of the two positions: the Trendelenburg position with hip flexion (hip flexion group, n = 20) and the Trendelenburg position without hip flexion (control group, n = 20). Each assigned position was maintained for 5 min and then patients were returned to the horizontal supine position. Spinal block level was assessed by pinprick, cold sensation, and modified Bromage scale at intervals for the following 150 min. RESULTS: The maximum level of pinprick and cold sensory block [median (range)] was higher in the hip flexion group [T4 (T8-C6) and T3 (T6-C2)] compared with the control group [T7 (T12-T4) and T5 (T11-T3)] (P < 0.001). The maximum motor blockade median (range) was not different between the two groups being 3 (3-3) in the hip flexion group vs 3 (0-3) in the control group. CONCLUSIONS: When the level of spinal anaesthesia is lower than required, flexion of the hips in the Trendelenburg position may be useful as a strategy attempt to increase the level of the block.ope

Analyses of the frequency and the indications of succinylcholine in general inhalation anesthesia

Background Succinylcholine (Sch) has been considered to be the neuromuscular blockade (NMB) of choice in clinical anesthesia due to its rapid onset and short duration of action. Despite these clinical advantages, the use of Sch has decreased recently on account of its potentially fatal adverse effects such as cardiac arrest and malignant hyperthermia. The aim of this report was to analyze the frequency and the indications of Sch as well as to discover an alternative to decreasing the frequency of Sch use. Methods The medical records of a total of 33,972 cases under general anesthesia were collected retrospectively, and the frequency of Sch use and the reason for choosing Sch was analyzed. The side effects and other complications of Sch were also analyzed. Results A muscle relaxant was administered in 32,724 cases (96.3%) out of 33,972 cases, and Sch was used in 647 of these cases (1.9%). The reasons for choosing Sch were the rapid sequence induction (291 cases), short operation time (220 cases), recent food intake (51 cases), habitual use (78 cases) and reintubation (7 cases). There were 211 cases of the single administration of Sch and 13 cases in whom Sch was injected repeatedly. A non-depolarizing muscle relaxant (NDMR) was used after Sch administration in 423 cases. Precurarization was carried out in 434 cases (67%) and no severe complications were observed. Conclusions The frequency of using Sch use can be decreased by reducing the habitual use and choosing the intubating dose of the intermediate acting NDMR as an alternative.ope

Intravenous lidocaine prior to extubation reduces emergence agitation and cough in pediatric adenotonsillectomy under sevoflurane anesthesia

Background Sevoflurane is widely used to ambulatory pediatric anesthesia. But, sevoflurane is associated with a high incidence of emergence agitation in children. In this study, we examined the effect of single intravenous lidocaine prior to extubation on emergence agitation and cough in children undergoing adenotonsillectomy. Methods All patients received a standardized anesthetic regimen with 2-3% sevoflurane in 50% O2/N2O after anesthetic induction with intravenous glycopyrrolate 0.004 mg/kg, thiopental 5 mg/kg and vecuronium 0.1 mg/kg. In a double-blinded trial, 120 children (3-9 years) were randomly assigned to receive normal saline 0.1 ml/kg (Group C), 1% lidocaine 1 mg/kg (Group L1) or 2% lidocaine 2 mg/kg (Group L2), at 1 min after beginning of spontaneous respiration. After extubation, the sedation score and the incidence of agitation and cough were recorded. Results The incidence of agitation and cough in Group L1 and L2 were significantly less than Group C (P < 0.05). At 5 min after arrival at postanesthetic care unit (PACU), more patients in Group L1 and L2 were in deeper sedation (the sedation score ≥ 2) than Group C. More patients in Group L1 were in deeper sedation than Group L2 and C at 10 min after arrival at PACU. Conclusions We conclude that intravenous lidocaine prior to extubation reduces emergence agitation and cough after sevoflurane anesthesia in children undergoing adenotonsillectomy.ope

Airway Management for General Anesthesia in a Patient with Severe Trismus due to Temporomandibular Joint Ankylosis

An ankylosis of temporomandibular joint (TMJ) can cause severe trismus, thus it may bring on many difficulties in airway management such as orotracheal intubation or laryngeal mask airway insertion. Such difficulties may cause serious complications related to airway management because the trismus due to ankylosis of TMJ can not be improved by administration of muscle relaxants or deep anesthesia in most cases.We report a case of nasotracheal intubation guided by a fiberoptic bronchoscope in a male patient with severe trismus due to TMJ ankylosis, who was scheduled for undergoing ophthalmic surgeryope

Myoclonic Movements Occurred After Combined Spinal-Epidural Anesthesia

Two cases showed intermittent myoclonic movements in the lower extremities after receiving combined spinal-epidural anesthesia (CSE). Case 1: A 73-year-old female patient, underwent CSE, for a total knee replacement of right leg. Anesthesia was performed at L3/4 interspace with 2.0 ml of 0.5% tetracaine, mixed with normal saline and patient's own cerebrospinal fluid and epinephrine 1:200,000. Epidural catheter was inserted 3 cm-cephalad. Patient-controlled analgesia regimen was made with sufentanil 100 ug, 0.75% ropivacaine 30 ml, and naloxone 0.55 mg, with normal saline. The infusion regimen began at the end of the surgery, finished uneventfully after one and half hours. After 3 hours, the patient developed symmetric hip adductions of large amplitude and extensions of both legs for 2 to 3 seconds. Until valproate 800 mg was given, the movements repeated at 1 to 2 minute intervals for 3 hours. Case 2:The anesthesia and analgesia for 74-year-old female patient was done in similar fashion. Three hours after the end of operation, the patient showed myoclonic movements on right leg for about 30 seconds. The movements occurred at 2-3 minute intervals for the subsequent 2 hours and resolved spontaneously.ope

optimal temperature of biofilm formation and comparison of inactivation effects according to materials

학위논문 (석사)-- 서울대학교 대학원 : 농업생명과학대학 농생명공학부, 2019. 2. 강동현.Biofilms have emerged as problems in food industry because of ability to form on food or food-contact surface in various conditions when surface bacteria were not properly removed Staphylococcus aureus which is one of prevalent pathogens in food industry can develop biofilm structure onto abiotic surfaces, causing cross-contamination. In comparison to 15 and 25℃ which maintain relatively consistent population over 7.0 log CFU/cm2, cell population at 37℃ increased in day 1 followed by constant decline. Thermal treatment inactivated 5-log population of biofilm cells when treated with 10 s at all conditions except for 25℃ in day 5. Also, when treated with non-thermal treatment, ca 1-log of biofilm cells was eliminated at 25℃ in day 5 while it resulted in over 2-log reduction in the other experimental conditions. To account for these phenomena, we conducted EPS quantification experiment using 96-well and stainless steel. In 96-well experiment, we found that highest amount of polysaccharide was secreted at the temperature of 25℃, while total biomass and protein contents produced at 37℃ was greatest. However, previous studies show that main component for EPS secreted by S. aureus is polysaccharide. Thus, we could conclude that biofilm formed at 25℃ for 5 days exhibited highest resistance to thermal and nonthermal treatment due to enhanced ability for exopolysaccharide secretion. We investigated the effect of saturated steam (SS) at 100°C and superheated steam (SHS) at 125°C and 150°C for inactivation of S. aureus biofilm in 4 types of coupons (STS No.4, STS 2B, HDPE, PP). We also identify material properties of each type of coupons to develop material factors affecting steam treatment. In all types of coupon, higher temperature and more superheated steam accomplished higher log reduction and need less time to reach below detection limit. S. aureus biofilm in steel type coupon is more susceptible than plastic type coupons under steam treatment. In this study two surface properties, which is roughness and hydrophobicity, did not have a significant effect on inactivation of biofilm in coupons by steam treatment. In contrast, thermal conductivity and thermal diffusivity had similar tendency of inactivation. S. aureus biofilm in higher thermal conductivity coupons were susceptible when steam was applied. Therefore, SHS treatment could be used to inactivate S. aureus biofilm in food-accessible surfaces and treatment time depended on the thermal conductivity of surfaces.표면에 세균이 적절히 제거 되지 않았을 경우, 다양한 환경 조건에서도 균이 바이오필름을 형성하며 특히 식품 산업에서 식품이나 식품 접촉면에 형성할 수 있어 문제로 대두되고있다. 이 때, 식품 산업에서 중요한 병원균 중 하나인 황색포도상구균은 표면에 바이오필름을 형성할 수 있는 대표균 중 하나 이며, 이에 따른 교차 오염의 위험이 있다. 황색포도상구균을 15°C, 25°C 그리고 37°C 에서 5일 동안 바이오필름을 형성시키면서 균의 수 변화를 확인한 결과, 15°C나 25°C에서는 7.0 log CFU/cm2이상의 상대적으로 일정한 값을 가지며, 37°C에서는 1일 째에 폭발적으로 증가하지만 그 이후 계속 감소하였다. 증기처리로 열 저항성을 확인한 결과, 5일 차에 25°C를 제외한 모든 조건에서 10 초간 처리하였을 때, 5 로그 이상 균이 저감화 되었다. 또한 차아염소산나트륨 10 ppm으로 비 열처리를 하였을 때, 25°C에서는 약 1 로그의 균 저감화를 보였지만 나머지 조건에서는 2 로그 이상이 저감화 되었다. 이러한 현상을 설명하기 위해 96-well 실험에서 25°C에서 다당류의 분비량이 가장 많았으며, 37°C에서는 생산된 총 바이오매스와 단백질의 함량이 가장 높았다. 하지만 이전 연구에서도 밝혀진 바로는 황색포도상구균이 분비하는 EPS의 주성분이 다당류였다. 따라서 우리는 25°C에서 5일 동안 형성된 바이오필름이 외부에 다당류를 가장 많이 분비하여 외부 자극에 대한 저항성을 갖춘 것이라고 해석할 수 있었다. 이어 우리는 4 종류의 쿠폰 (스테인리스 강 No.4, 스테인리스 강 2B, 고밀도 폴리에틸렌, 폴리프로필렌)에서 황색포도상구균이 바이오필름을 형성하였을 때 이를 100°C의 포화 증기와 125°C, 150°C의 초고온 과열 증기로 불활성화하는 실험을 진행하였다. 또한 증기 처리에 영향을 미치는 물질적인 요인을 밝히기 위해 각 유형의 쿠폰에 거칠기와 소수성 그리고 열전도도를 측정하였다. 모든 종류의 쿠폰에서 더 높은 온도와 더 많이 과열된 증기가 높은 균의 로그 저감화를 보였고 검출 한계 이하로 도달하는데 걸리는 시간 또한 짧았다. 증기 처리를 스틸 계열의 쿠폰에서 형성된 바이오필름에 하는 것이 플라스티 계열의 쿠폰보다 내부의 균을 더 빠르게 저감화 할 수 있었다. 본 연구에서 표면의 거칠기와 소수성은 증기 처리로 쿠폰위에 형성된 바이오필름을 불활성화하는데 영향을 미치지 않았다. 반면, 열전도도나 열확산율은 증기로 여러 재질위의 바이오필름을 제어하는 것과 가장 유사한 경향을 보였다. 높은 열전도도를 가진 쿠폰일수록 저감화 효과가 더 잘 일어났다. 라서 황색포도상구균이 바이오필름을 형성하여 이를 제어할 때 초고온 과열증기를 활용할 수 있고, 그 처리시간은 열전도도에 따라 달라질 수 있다.I. INTRODUCTION 1 II. MATERIALS AND METHODS. 6 2.1. Bacterial cultures and cell suspension 6 2.2. Optimal conditions for biofilm formation depending on temperature 7 2.2.1. Coupons preparation. 7 2.2.2. Biofilm formation assay. 7 2.2.3. Steam treatment (thermal resistance) 8 2.2.4. NaOCl treatment (non-thermal resistance). 9 2.2.5. Bacterial enumeration. 9 2.2.6. EPS quantification 10 2.3. Comparison of S. aureus in biofilm reduction on 4 types of food contact surface 11 2.3.1. Coupons preparation 11 2.3.2. Biofilm formation assay 12 2.3.3. Saturated steam (SS) and superheated steam (SHS) treatment 12 2.3.4. Bacterial enumeration 13 2.3.5. Surface hydrophobicity and roughness measurement 14 2.3.6. Thermal conductivity and Thermal diffusivity measurement. 15 2.4. Statistical analysis. 15 III. RESULTS 16 3.1. Optimal conditions for biofilm formation depending on temperature 16 3.1.1. biofilm maturation curve. 16 3.1.2. Comparison of heat resistance of S. aureus in biofilm 18 3.1.3. Comparison of chemical resistance of S. aureus in biofilm. 22 3.1.4. Changes in EPS amount as the S. aureus biofilm maturated. 25 3.2. Inactivation of S. aureus biofilm on the food contact surfaces by superheated steam treatment 27 3.2.1. Superheated steam and saturated steam treatment on S. aureus biofilm on 4 types of coupons. 27 3.2.2. Material properties of coupons 33 IV. DISCUSSIONS. 35 V. REFERENCES. 44 VI. 국문초록 56Maste