Boonstra Elles C, Agresti Liliana, van der Mei Henny C, Jutte Paul C, Sjollema Jelmer
Department of Orthopedics, University Medical Center Groningen, Hanzeplein 1, Groningen, The Netherlands.
Department of Biomaterials and Biomedical Technology, University Medical Center Groningen, Antonius Deusinglaan 1, Groningen, The Netherlands.
BMC Microbiol. 2025 Jan 11;25(1):12. doi: 10.1186/s12866-024-03674-x.
In vivo evaluations of the antimicrobial efficacy of biomaterials often use bioluminescent imaging modalities based on bioluminescent bacteria to allow follow-up in single animals. Bioluminescence production by bacteria is dependent on their metabolic activity. It is well known that several factors can influence the metabolism of bacteria, such as the use of antimicrobials and changes in bacterial growth phase. However, little is known about the influence of intracellular residence of bacteria on bioluminescence. For example, Staphylococcus aureus can survive in the peri-implant tissue and is known to survive intracellularly in macrophages.
In this study, we evaluated the bioluminescent radiance of S. aureus upon phagocytosis by macrophages. We showed that S. aureus reduced its bioluminescence upon phagocytosis by macrophages compared to S. aureus in a single culture. Simultaneously, bacterial numbers as measured by colony-forming units remained constant over time. S. aureus was released extracellularly as a result of macrophage cell death. Following this release, the bacteria increased their bioluminescence again. Replenishment of fresh macrophages showed an immediate increase in bioluminescence. Moreover, the addition of fresh macrophages showed a diminished decrease in bioluminescence at 24 h of coculture, but this effect did not last.
Together, this study demonstrates that phagocytosis by macrophages decreases bioluminescence of S. aureus, which is an important factor to consider when using bioluminescent imaging to study the infection process in an in vivo model.
生物材料抗菌功效的体内评估通常使用基于生物发光细菌的生物发光成像模式，以便对单个动物进行跟踪。细菌产生生物发光取决于其代谢活性。众所周知，有几个因素会影响细菌的代谢，如抗菌药物的使用和细菌生长阶段的变化。然而，关于细菌细胞内驻留对生物发光的影响知之甚少。例如，金黄色葡萄球菌可以在植入物周围组织中存活，并且已知可以在巨噬细胞内生存。
在本研究中，我们评估了巨噬细胞吞噬后金黄色葡萄球菌的生物发光强度。我们发现，与单一培养中的金黄色葡萄球菌相比，巨噬细胞吞噬后的金黄色葡萄球菌生物发光强度降低。同时，通过菌落形成单位测量的细菌数量随时间保持恒定。由于巨噬细胞死亡，金黄色葡萄球菌被释放到细胞外。释放后，细菌的生物发光强度再次增加。补充新鲜巨噬细胞后，生物发光强度立即增加。此外，添加新鲜巨噬细胞显示共培养24小时时生物发光强度的下降有所减少，但这种效果并未持续。
总之，本研究表明巨噬细胞吞噬会降低金黄色葡萄球菌的生物发光，这是在使用生物发光成像研究体内模型感染过程时需要考虑的一个重要因素。
