Verheul Marielle, Wagenmakers Anne A, Nelissen Rob G H H, Nibbering Peter H, Pijls Bart G
Department of Orthopedics, Leiden University Center for Infectious Diseases (LUCID), Leiden University Medical Center, Leiden, Netherlands.
Leiden University Center for Infectious Diseases (LUCID), Leiden University Medical Center, Leiden, Netherlands.
Bone Joint Res. 2025 May 20;14(5):485-494. doi: 10.1302/2046-3758.145.BJR-2024-0341.R1.
Fracture-related infections and the associated treatment failure burden our society and healthcare system significantly. As an alternative approach, we investigated the effect of non-contact induction heating (NCIH) against within mature biofilms. In addition, we assessed the ability of antibiotics, the antimicrobial peptide SAAP-148, and bacteriophage (phage) ISP to enhance the efficacy of NCIH, thereby allowing the use of lower temperatures during NCIH.
Clinical isolates of methicillin-resistant and methicillin-sensitive (methicillin-resistant (MRSA), methicillin-sensitive (MSSA)) were cultured for seven days on Ti-6Al-7Nb (mimicking fracture plates) discs to obtain mature biofilms. Biofilms were exposed to 60°C to 80°C NCIH. In addition, biofilms were sequentially exposed to 60°C to 70°C NCIH and rifampicin/ciprofloxacin, SAAP-148, or phage ISP. Biofilm-embedded bacteria were harvested by sonication to determine the bacterial load and visualized by confocal microscopy (LIVE/DEAD).
NCIH to 60°C, 70°C, and 80°C reduced biofilm-embedded MRSA and MSSA by 2.3-log, 4.9-log, 5.5-log, and 1.1-log, 3.4-log, and 6.6-log CFU/ml, respectively. LIVE/DEAD staining revealed NCIH-induced bacterial cell death throughout the biofilm layers. The sequential combination of rifampicin/ciprofloxacin at 10 µg/ml and 1,280 µg/ml (MRSA) or 156 µg/l and 64 µg/ml (MSSA) and 70°C NCIH synergistically reduced biofilm-embedded bacteria by 2.7-log and 3.7-log CFU/ml, respectively, while the alternating exposure order reduced bacterial counts by -0.1 and 1.7-log CFU/ml. SAAP-148 at 51.2 µM followed by 70°C NCIH further diminished biofilm-embedded MRSA and MSSA by 2.3-log and 1.5-log CFU/ml, respectively. No significant reductions were observed for NCIH combined with phage ISP compared to these treatments alone.
NCIH effectively reduced biofilm-embedded on Ti-6Al-7Nb in a heat-dependent fashion. Rifampicin/ciprofloxacin and SAAP-148, but not phage ISP, enhanced the efficacy of NCIH. Antibiotic exposure at suboptimal concentrations followed by NCIH was more effective than vice versa, suggesting that the application of this approach might be most suitable in clinical situations where antibiotic treatment has already started.
骨折相关感染及其所致的治疗失败给社会和医疗系统带来了沉重负担。作为一种替代方法，我们研究了非接触感应加热（NCIH）对成熟生物膜内细菌的作用。此外，我们评估了抗生素、抗菌肽SAAP - 148和噬菌体ISP增强NCIH疗效的能力，从而在NCIH过程中允许使用更低的温度。
耐甲氧西林金黄色葡萄球菌和甲氧西林敏感金黄色葡萄球菌（耐甲氧西林金黄色葡萄球菌（MRSA）、甲氧西林敏感金黄色葡萄球菌（MSSA））的临床分离株在Ti - 6Al - 7Nb（模拟骨折钢板）圆盘上培养7天以获得成熟生物膜。生物膜暴露于60°C至80°C的NCIH。此外，生物膜依次暴露于60°C至70°C的NCIH以及利福平/环丙沙星、SAAP - 148或噬菌体ISP。通过超声处理收获生物膜包裹的细菌以确定细菌载量，并通过共聚焦显微镜（死活染色）进行可视化。
60°C、70°C和80°C的NCIH分别使生物膜包裹的MRSA减少2.3个对数、4.9个对数、5.5个对数CFU/ml，使MSSA减少1.1个对数、3.4个对数和6.6个对数CFU/ml。死活染色显示NCIH诱导生物膜各层细菌细胞死亡。10μg/ml和1280μg/ml（MRSA）或156μg/l和64μg/ml（MSSA）的利福平/环丙沙星与70°C的NCIH联合使用分别协同减少生物膜包裹细菌2.7个对数和3.7个对数CFU/ml，而交替暴露顺序使细菌数量减少0.1和1.7个对数CFU/ml。51.2μM的SAAP - 148随后进行70°C的NCIH进一步分别使生物膜包裹的MRSA和MSSA减少2.3个对数和1.5个对数CFU/ml。与单独使用这些处理相比，NCIH联合噬菌体ISP未观察到显著的细菌数量减少。
NCIH以热依赖方式有效减少Ti - 6Al - 7Nb上生物膜包裹的金黄色葡萄球菌。利福平/环丙沙星和SAAP - 148而非噬菌体ISP增强了NCIH的疗效。次优浓度的抗生素暴露后进行NCIH比反之更有效，这表明该方法的应用可能最适用于已经开始抗生素治疗的临床情况。
