鶏肉類の病原微生物による食中毒リスクの解明と低減策への提言

• Material Type: 博士論文
• Title: 鶏肉類の病原微生物による食中毒リスクの解明と低減策への提言
• Author/Editor: 山本, 倫也
• Author Heading: 山本, 倫也
• Publication, Distribution, etc.: 山口県立大学大学院健康福祉学研究科
• Publication Date: 2023-03-15
• Publication Date (W3CDTF): 2023-03-15
• Alternative Title: Studies on Elucidation of the Risk of Food borne Diseases by Pathogenic Microorganisms in Chicken Meat and Recommendations for Reduction Measures
• Degree grantor/type: 山口県立大学
• Date Granted: 2023-03-15
• Dissertation Number: 甲第27号
• Degree Type: 博士（健康福祉学）
• Text Language Code: jpn
• Target Audience: 一般
• Note (General): 本研究は，鶏肉類のフードチェーン各段階における病原微生物の汚染実態の調査を実施し，食中毒リスクの解明と低減策の検討を行った． 流通段階における調査により，山口県内の市販鶏肉類の35.7%からカンピロバクターが分離され，レバー等の特定の部位や夏季の汚染率が高いといった実態が明らかになった．また，mP-BIT法による分離株の遺伝子型別により，病原性関連遺伝子を保有する菌などが確認されるとともに，感染症治療の難渋化が懸念されるフルオロキノロン系耐性菌の汚染も確認された．このことから，本県に流通する市販鶏肉類は，流通段階までに十分な食中毒リスクの低減が図られていないことが示唆された．このため，鶏肉類の消費段階におけるリスク低減策を優先的に進めることが重要と考えられ，消費者等に対する食中毒防止に係る啓発等を一層進めていく必要がある． 食鳥処理段階における調査により，山口県内の大規模食鳥処理場から出荷される鶏肉類がカンピロバクターに汚染されており，当該施設における次亜塩素酸ナトリウムを用いた冷却工程による消毒では，十分な食中毒リスクの低減が図られていないと考えられた．今後，施設の処理羽数や設備等の実態に応じ，消毒薬の種類，使用濃度や冷却時間等の衛生管理の改善が必要である．また，併せて，各生産農場における鶏の汚染防除策の検討を進めていく必要があると考えられた． 生産段階である複数農場の調査により，農場のカンピロバクター陽性率は中国地方が46.9%，九州地方が75.0%，サルモネラ陽性率は中国地方が84.4%，九州地方が89.3%であった．地域により，農場や鶏群の汚染状況，菌種や血清型，遺伝子型や薬剤耐性獲得状況等について特徴がみられた．このことから，鶏肉類の食中毒リスクの解明及び低減策の検討に当たっては，地域性を十分に考慮することが重要と考えられ，汚染実態を適切に把握するための体制の構築が必要である．農場及び鶏舎の汚染要因等の検討に係る調査により，鶏舎内外の環境や飼料等はカンピロバクターの侵入・拡散の要因にならないものの，入雛5～6週以降の感染した鶏の糞便等を介して飼養環境中に汚染が拡散したことが示唆された．また，サルモネラについては，鶏舎の敷料（発酵堆積糞）を含む飼養環境における菌の継続的な汚染が確認された．飼料や作業員等を介したサルモネラの拡散が示唆される結果も得られたことから，食中毒リスクの低減のためには，農場の飼養衛生管理マニュアルの改善や危害要因分析重要管理点（HACCP）に基づく衛生管理の導入による対策強化を図る必要がある．特に，敷料（発酵堆積糞）の衛生管理に係る重要管理点（CCP）を設定し，菌を完全に死滅させることができる発酵温度や時間の検証等が必要である． 食鳥処理段階や生産段階におけるHACCPに基づく適切な衛生管理の推進等のためには，行政の衛生部局や畜産部局，研究機関，事業者，消費者等の様々な主体による分野横断的な連携・協働の下，本研究で得られた知見を基に，鶏肉類のフードチェーン各段階において効果的な食中毒リスク低減策を講じ，食の安心・安全の確保を進めていくことが必要である．; This study was conducted to investigate the actual contamination of chicken meat with pathogenic microorganisms at each stage of the food chain, to clarify the risk of foodborne diseases, and to examine measures to reduce the risk. The survey at the distribution stage revealed that Campylobacter was isolated from 35.7% of commercial chicken meat in Yamaguchi Prefecture, and that the contamination rate was high in specific parts such as liver and during the summer season. Genotyping of the isolates by the mP-BIT method confirmed the presence of pathogenic genes and a high level of contamination with fluoroquinolone-resistant bacteria, which are feared to make treatment of infectious diseases more difficult. These results suggest that the disinfection of commercial chicken meat distributed in this prefecture is not sufficiently reduced in terms of foodborne diseases risk by the time they reach the distribution stage. Therefore, it is important to prioritize risk reduction measures at the consumption stage of chicken meat, and it is necessary to further educate consumers on the prevention of foodborne diseases. A survey at the chicken slaughtering stage showed that chicken meat shipped from a chicken slaughterhouse in Yamaguchi Prefecture was highly contaminated with Campylobacter, and that the disinfection of chicken meat by the cooling process using sodium hypochlorite at the facility was not sufficient to reduce the risk of foodborne diseases. In the future, it is necessary to improve sanitation management, such as the type of disinfectant, concentration used, and cooling time, in accordance with the actual conditions of the number of broiler processed and equipment at the facility. In addition, it was considered necessary to examine measures to prevent contamination of broiler at each production farm. A survey of several farms at the production stage revealed that the Campylobacter-positive rate was 46.9% in the Chugoku region and 75.0% in the Kyushu region, and the Salmonella-positive rate was 84.4% in the Chugoku region and 89.3% in the Kyushu region. The different characteristics of the contamination status of farms and broiler flocks, the bacterial species and serotypes, genotypes, and the acquisition of drug resistance were observed in the different regions. Therefore, it is important to take regional characteristics into consideration when clarifying the risk of foodborne diseases of chicken meat and considering measures to reduce the risk. The investigation of contamination factors in farms and broiler houses suggested that although the environment inside and outside the broiler house and feed were not factors for Campylobacter invasion and spread, contamination spread to the feeding environment through feces of infected broiler after 5 to 6 weeks of brooding. In addition, continuous contamination of Salmonella was confirmed in the feeding environment, including the bedding material (recycled fermented litter) of the broiler house. The results also suggested the spread of Salmonella through feed and workers. Therefore, it is necessary to strengthen measures to reduce the risk of food poisoning by improving farm broiler feeding hygiene management manuals and introducing hygiene management based on Hazard Analysis and Critical Control Point (HACCP). In particular, it is necessary to establish Critical Control Points for sanitary management of bedding (recycled fermented litter) and to verify fermentation temperatures and times that can completely destroy the bacteria. In order to promote appropriate sanitary management based on HACCP at the chicken slaughtering and production stages, effective foodborne diseases risk reduction measures should be implemented at each stage of the chicken meat food chain based on the knowledge obtained in this study under cross-field collaboration and cooperation among various entities such as government health departments, livestock breeding departments, research institutes, businesses, and consumers. Based on the findings of this study, it is necessary to take effective measures to reduce the risk of foodborne diseases at each stage of the chicken meat food chain to ensure food safety and security.
• Source: fulltext; http://ypir.lib.yamaguchi-u.ac.jp/yp/1799/files/166801; http://ypir.lib.yamaguchi-u.ac.jp/yp/1799/files/166802
• Access Restrictions: インターネット公開
• Data Provider (Database): 国立情報学研究所 : 学術機関リポジトリデータベース（IRDB）（機関リポジトリ）; https://irdb.nii.ac.jp
• Original Data Provider (Database): 山口県立大学 : 山口県立大学学術機関リポジトリ