Roopkhan Naritsara, Chaianunporn Thotsapol, Chareonsudjai Sorujsiri, Chaianunporn Kanokporn
Department of Environmental Science, Faculty of Science, Khon Kaen University, Khon Kaen, Thailand.
Department of Microbiology, Faculty of Medicine, Khon Kaen University, Khon Kaen, Thailand.
PeerJ. 2025 Feb 28;13:e19051. doi: 10.7717/peerj.19051. eCollection 2025.
is a soil- and water-dwelling bacterium that causes the life-threatening infection melioidosis. Patients typically acquire this infection through environmental exposure, so reducing levels in the environment could mitigate the risk of infection. is a biological control agent that synthesizes a diverse range of antimicrobial substances targeting other microorganisms. This study therefore examined the antibacterial and anti-biofilm activities of culture filtrate against .
The antibacterial activities of culture filtrates, collected at various time intervals, were assessed against using the agar well diffusion method. Subsequently, the minimum inhibitory concentrations (MICs), minimum bactericidal concentrations (MBCs), and anti-biofilm activities of the culture filtrate exhibiting the highest inhibitory effect were determined. Bactericidal efficacy was further evaluated via a time-kill assay. The mechanisms underlying inhibition were then investigated using scanning electron microscopy and crystal violet uptake assays.
Filtrate collected from 7-day old cultures of (TD7) exhibited the strongest inhibitory effect on , with an inhibition zone of 30.33 ± 0.19 mm. The MIC of TD7 against was 7.81 ± 0.00 mg/mL and the MBC ranged from 7.81 ± 0.00 to 11.72 ± 1.75 mg/mL. Time-kill studies with TD7 confirmed its bactericidal activity, with complete elimination of occurring within 30 min treatment at 62.48 mg/mL (8xMIC) and 24 h treatment at 7.81 mg/mL (1xMIC). At a concentration of 7.81 mg/mL, TD7 also significantly reduced biofilm formation. Scanning electron microscopy revealed surface roughening and cell shrinkage of TD7-treated . TD7-treated bacteria were also found to absorb more crystal violet dye than untreated cells, indicating that TD7 might inhibit and kill by disrupting cell membrane permeability.
Our findings demonstrate that culture filtrates possess bactericidal activity and effectively disrupt biofilm formation by . This suggests that could potentially be used to reduce the presence of in the environment and, consequently, lower the incidence of melioidosis.
是一种生活在土壤和水中的细菌，可引起危及生命的类鼻疽感染。患者通常通过环境暴露感染此病，因此降低环境中的水平可降低感染风险。是一种生物防治剂，能合成多种针对其他微生物的抗菌物质。因此，本研究检测了培养滤液对的抗菌和抗生物膜活性。
采用琼脂孔扩散法评估在不同时间间隔收集的培养滤液对的抗菌活性。随后，测定表现出最高抑制作用的培养滤液的最低抑菌浓度（MIC）、最低杀菌浓度（MBC）和抗生物膜活性。通过时间杀灭试验进一步评估杀菌效果。然后使用扫描电子显微镜和结晶紫摄取试验研究抑制的潜在机制。
从7天龄培养物中收集的滤液（TD7）对表现出最强的抑制作用，抑菌圈为30.33±0.19毫米。TD7对的MIC为7.81±0.00毫克/毫升，MBC范围为7.81±0.00至11.72±1.75毫克/毫升。TD7的时间杀灭研究证实了其杀菌活性，在62.48毫克/毫升（8倍MIC）处理30分钟和7.81毫克/毫升（1倍MIC）处理24小时内可完全消除。在7.81毫克/毫升的浓度下，TD7还显著减少了生物膜的形成。扫描电子显微镜显示，经TD7处理的表面粗糙化和细胞收缩。还发现经TD7处理的细菌比未处理的细胞吸收更多的结晶紫染料，表明TD7可能通过破坏细胞膜通透性来抑制和杀死。
我们的研究结果表明，培养滤液具有杀菌活性，并能有效破坏生物膜的形成。这表明可能潜在地用于减少环境中的存在，从而降低类鼻疽的发病率。
