Rungrojn Artharee, Abdad Mohammad Yazid, Dhawan Sandhya, Wongsantichon Jantana, Blacksell Stuart D
Mahidol Oxford Tropical Medicine Research Programme, Faculty of Tropical Medicine, Mahidol University, 420/6 Rajvithi Road, Bangkok, 10400, Thailand.
Centre for Tropical Medicine and Global Health, Nuffield Department of Medicine, University of Oxford, Oxford, OX3 7LG, UK.
Sci Rep. 2025 Jul 1;15(1):20642. doi: 10.1038/s41598-025-06728-w.
Heat treatment, or thermal disinfection, is one of the simplest and most widely used methods for microbial inactivation. Proper heat inactivation protocols are essential to ensure the safe transportation and handling of infectious materials, particularly for organisms in risk group 3, such as Rickettsia and Orientia. In this study, we examined the inactivation of four bacterial species-Orientia tsutsugamushi, Rickettsia typhi, Rickettsia conorii, and Rickettsia honei-at temperatures of 56 °C, 80 °C, and 90 °C for durations of 5, 15, 30, and 60 min. Observations were made at 0, 1, 3, 7, 10, and 14 days post-infection (dpi) to assess bacterial infectivity by monitoring bacterial DNA copies in newly infected cells. Our results indicate that 56 °C for 5 min was the minimum temperature and time required to inactivate O. tsutsugamushi, R. typhi, R. conorii, and R. honei. O. tsutsugamushi exhibited a higher reduction factor at 56 °C compared to R. typhi, R. conorii, and R. honei. Additionally, a strong inverse correlation between incubation time and log10 reduction factor was observed for O. tsutsugamushi and R. typhi, underscoring the importance of both time and temperature in effective heat treatment. However, no such correlation was observed for R. conorii and R. honei. These findings highlight the variable responses of bacteria to heat, emphasizing the need for pathogen-specific approaches in inactivation protocols. Optimizing heat treatment strategies based on these insights is critical for enhancing biosafety and ensuring effective pathogen eradication.
热处理或热消毒是微生物灭活最简单、使用最广泛的方法之一。适当的热灭活方案对于确保传染性材料的安全运输和处理至关重要，特别是对于风险组3中的生物体，如恙虫病东方体和嗜吞噬细胞无形体。在本研究中，我们在56°C、80°C和90°C的温度下，对恙虫病东方体、伤寒立克次体、康氏立克次体和霍氏立克次体这四种细菌进行了5、15、30和60分钟的灭活处理。在感染后0、1、3、7、10和14天进行观察，通过监测新感染细胞中的细菌DNA拷贝数来评估细菌的传染性。我们的结果表明，56°C处理5分钟是灭活恙虫病东方体、伤寒立克次体、康氏立克次体和霍氏立克次体所需的最低温度和时间。与伤寒立克次体、康氏立克次体和霍氏立克次体相比，恙虫病东方体在56°C时表现出更高的降低系数。此外，观察到恙虫病东方体和伤寒立克次体的孵育时间与log10降低系数之间存在强烈的负相关，强调了时间和温度在有效热处理中的重要性。然而，康氏立克次体和霍氏立克次体未观察到这种相关性。这些发现突出了细菌对热的不同反应，强调了在灭活方案中采用病原体特异性方法的必要性。基于这些见解优化热处理策略对于提高生物安全性和确保有效根除病原体至关重要。
