Nunez Charles, Kostoulias Xenia, Peleg Anton, Short Francesca, Qu Yue
Infection Program, Monash Biomedicine Discovery Institute, Department of Microbiology, Monash University, Clayton, Victoria, 3800, Australia.
Department of Infectious Diseases, The Alfred Hospital and Central Clinical School, Monash University, Melbourne, Victoria, 3004, Australia.
Biofilm. 2023 Jan 22;5:100105. doi: 10.1016/j.bioflm.2023.100105. eCollection 2023 Dec.
Biofilm formation and capsule production are known microbial strategies used by bacterial pathogens to survive adverse conditions in the hospital environment. The relative importance of these strategies individually is unexplored. This project aims to compare the contributory roles of biofilm formation and capsule production in bacterial survival on hospital surfaces. Representative strains of bacterial species often causing hospital-acquired infections were selected, including , , , and . The importance of biofilm formation and capsule production on bacterial survival was evaluated by comparing capsule-positive wild-type and capsule-deficient mutant strains, and biofilm and planktonic growth modes respectively, against three adverse hospital conditions, including desiccation, benzalkonium chloride disinfection and ultraviolet (UV) radiation. Bacterial survival was quantitatively assessed using colony-forming unit (CFU) enumeration and the 2,3-bis-(2-methoxy-4-nitro-5-sulfophenyl)-2H-tetrazolium-5-carboxanilide (XTT) assay and qualitatively by scanning electron microscopy (SEM). Correlations between capsule production and biofilm formation were further investigated. Biofilm formation contributed significantly to bacterial survival on hospital surface simulators, mediating high resistance to desiccation, benzalkonium chloride disinfection and UV radiation. The role of capsule production was minor and species-specific; encapsulated but not cells demonstrated slightly increased resistance to desiccation, and neither showed enhanced resistance to benzalkonium chloride. Interestingly, capsule production sensitized and to UV radiation. The loss of capsule in and enhanced biofilm formation, possibly by increasing cell surface hydrophobicity. In summary, this study confirms the crucial role of biofilm formation in bacterial survival on hospital surfaces. Conversely, encapsulation plays a relatively minor role and may even negatively impact bacterial biofilm formation and hospital survival.
生物膜形成和荚膜产生是已知的细菌病原体用于在医院环境的不利条件下生存的微生物策略。这些策略各自的相对重要性尚未得到探索。本项目旨在比较生物膜形成和荚膜产生在细菌在医院表面存活中的作用。选择了经常引起医院获得性感染的代表性细菌菌株，包括[具体菌株名称1]、[具体菌株名称2]、[具体菌株名称3]、[具体菌株名称4]和[具体菌株名称5]。通过分别比较荚膜阳性野生型和荚膜缺陷突变菌株以及生物膜和浮游生长模式，针对三种不利的医院条件，包括干燥、苯扎氯铵消毒和紫外线（UV）辐射，评估生物膜形成和荚膜产生对细菌存活的重要性。使用菌落形成单位（CFU）计数和2,3-双-（2-甲氧基-4-硝基-5-磺基苯基）-2H-四唑-5-甲酰苯胺（XTT）测定法定量评估细菌存活，并通过扫描电子显微镜（SEM）进行定性评估。进一步研究了荚膜产生与生物膜形成之间的相关性。生物膜形成对医院表面模拟器上的细菌存活有显著贡献，介导了对干燥、苯扎氯铵消毒和紫外线辐射的高抗性。荚膜产生的作用较小且具有物种特异性；有荚膜的[具体菌株名称6]细胞但不是[具体菌株名称7]细胞对干燥的抗性略有增加，并且两者对苯扎氯铵均未表现出增强的抗性。有趣的是，荚膜产生使[具体菌株名称8]和[具体菌株名称9]对紫外线辐射敏感。[具体菌株名称10]和[具体菌株名称11]中荚膜的丧失增强了生物膜形成，可能是通过增加细胞表面疏水性。总之，本研究证实了生物膜形成在细菌在医院表面存活中的关键作用。相反，荚膜化起相对较小的作用，甚至可能对细菌生物膜形成和医院存活产生负面影响。
