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Abstract：
Corynebacterium pseudotuberculosis is a gram-positive bacterium and is the etiologic agent of caseous lymphadenitis (CL) in small ruminants. This disease is characterized by the development of encapsulated granulomas in visceral and superficial lymph nodes, and its clinical treatment is refractory to antibiotic therapy. An important virulence factor of the Corynebacterium genus is the ability to produce biofilm; however, little is known about the characteristics of the biofilm produced by C. pseudotuberculosis and its resistance to antimicrobials. Silver nanoparticles (AgNPs) are considered as promising antimicrobial agents, and are known to have several advantages, such as a broad-spectrum activity, low resistance induction potential, and antibiofilm activity. Therefore, we evaluate herein the activity of AgNPs in C. pseudotuberculosis, through the determination of minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC), antibiofilm activity, and visualization of AgNP-treated and AgNP-untreated biofilm through scanning electron microscopy. The AgNPs were able to completely inhibit bacterial growth and inactivate C. pseudotuberculosis at concentrations ranging from 0.08 to 0.312 mg/mL. The AgNPs reduced the formation of biofilm in reference strains and clinical isolates of C. pseudotuberculosis, with interference values greater than 80% at a concentration of 4 mg/mL, controlling the change between the planktonic and biofilm-associated forms, and preventing fixation and colonization. Scanning electron microscopy images showed a significant disruptive activity of AgNP on the consolidated biofilms. The results of this study demonstrate the potential of AgNPs as an effective therapeutic agent against CL.
摘要：
假结核棒状杆菌是革兰氏阳性细菌，是小反刍动物干酪性淋巴结炎（CL）的病原体。这种疾病的特征是在内脏和浅表淋巴结中发生包裹性肉芽肿，其临床治疗难以用抗生素治疗。棒杆菌属的一个重要毒力因子是产生生物膜的能力；然而，关于假结核分枝杆菌产生的生物膜的特征及其对抗菌药物的抗性知之甚少。银纳米粒子（AgNPs）被认为是有前途的抗菌剂，并且已知有几个优点，比如广谱活动，低电阻感应电位，和抗生物膜活性。因此,我们在此评估AgNPs在假结核分枝杆菌中的活性，通过测定最小抑菌浓度(MIC),最小杀菌浓度（MBC），抗生物膜活性，通过扫描电子显微镜观察AgNP处理和AgNP未处理的生物膜。AgNP能够在0.08至0.312mg/mL的浓度范围内完全抑制细菌生长并灭活假结核分枝杆菌。AgNPs减少了假结核分枝杆菌的参考菌株和临床分离株中生物膜的形成，在浓度为4mg/mL时，干扰值大于80％，控制浮游和生物膜相关形式之间的变化，防止固定和定植。扫描电子显微镜图像显示AgNP对固结的生物膜具有显着的破坏活性。这项研究的结果证明了AgNP作为抗CL的有效治疗剂的潜力。
