Infection control index for preventing Bacillus cereus nosocomial outbreak

2018 Fiscal Year Final Research Report

• Project/Area Number: 15K08863
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Research Field: Medical and hospital managemen
• Research Institution: National Institute of Infectious Diseases
• Principal Investigator: Suzuki Satowa 国立感染症研究所, 薬剤耐性研究センター, 室長 (30373400)
• Co-Investigator(Kenkyū-buntansha): 東 秀明 北海道大学, 人獣共通感染症リサーチセンター, 教授 (20311227)
• Research Collaborator: Kobayashi Ayako
• Project Period (FY): 2015-04-01 – 2019-03-31
• Keywords: Bacillus cereus / 院内感染 / Bacillus属 / 季節性 / 病院環境 / MLST

Outline of Final Research Achievements

Bacillus cereus is ubiquitous in environment, but several nosocomial outbreaks of B. cereus blood stream infections including fatal cases were reported in Japan. Analysis of JANIS data showed diverse isolation rate of Bacillus spp. among hospitals in Japan. Isolation rate of B. cereus had clear seasonality which peaks in summer time but not in other Bacillus spp. Increase of isolation rate of total Bacillus spp. may reflect contamination of hospital environment by B. cereus. This was supported by species identification of all Bacillus spp. isolates from clinical samples of three hospitals. Molecular analysis of B. cereus isolates from nosocomial outbreaks revealed that unique sequence type (ST) 1420 was dominant. The ST1420 belonged to the Cereus III lineage which is close to the Anthracis lineages. Species identification and molecular analysis of Bacillus spp. in case of summer increase may useful for risk assessment to prevent future nosocomial B. cereus infection.

Free Research Field

感染症疫学　院内感染　薬剤耐性菌

Academic Significance and Societal Importance of the Research Achievements

Bacillus cereusによる血流感染は血液疾患などの患者では予後不良となりうるが、Bacillus属菌は環境に広く存在し、検体採取時の汚染菌でもあることからその分離率の推移は感染対策に活用されていなかった。
本研究により、検体の種類にかかわらずBacillus属菌の分離率が高いことは、院内感染としてのB. cereus血流感染集積のリスクであること、季節性を踏まえた分離数の推移を評価する必要性、Bacillus属菌分離率上昇時には菌種同定および特定クローン（ST1420）の検索も有用である可能性が示唆され、これらの知見はB. cereus院内感染の予防に資すると思われた