Ngwai Yakubu B, Adachi Yoshikazu, Ogawa Yasuki, Hara Hiromichi
Department of Microbiology, Human Virology and Biotechnology, National Institute for Pharmaceutical Research and Development, Abuja, Nigeria.
J Microbiol Immunol Infect. 2006 Aug;39(4):278-91.
Salmonella typhimurium DT104 strain has emerged as a global human and veterinary public health concern because of its antibiotic resistance and extensive host range. Although it is thought to be more virulent, to date, factors relevant to its virulence have not been fully elucidated. Thus, understanding how this strain forms biofilms on hydrophobic surfaces will add to current knowledge on its possible virulence mechanism.
Biofilm-forming abilities of clinical isolates of S. typhimurium DT104 from human and animal sources on hydrophobic inanimate surfaces were assessed by absorbance at 600 nm of crystal violet-bound cells recovered from 96-well tissue culture plates after growth in a nutrient-rich growth medium and various adjusted media; and scanning electron microscopy based on standard procedures.
In the nutrient-rich growth medium, Luria-Bertani (LB), biofilms were formed in small quantities, preferentially on polystyrene (p<0.05), and followed different time courses. Significantly lower amounts of biofilms were formed on polystyrene when a nutrient-deficient growth medium (adherence test medium) was used. Inclusion of D-(+)-mannose in LB at a concentration of 100 mM significantly (p<0.05) inhibited biofilm formation on polystyrene. D-(+)-glucose relatively enhanced biofilm formation but D-(-)-mannitol only insignificantly influenced the process. The action of mannose on polyvinly chloride (PVC) was insignificant, suggesting that its action may be surface-dependent. Additionally, glucose significantly reduced biofilm growths of 2 of the isolates and only that of the PVC-loving strain T980021 on polystyrene and PVC, respectively. At the concentration tested, unlike xylose, both D-mannose and D-glucose significantly (p<0.05) inhibited bacterial growth, providing a possible mechanism for their inhibitory action on biofilm formation by S. typhimurium. While stress of starvation resulted in significant reduction in biofilm formation on polystyrene in all but the PVC-loving strain T980021, high osmolarity had little effect on the quantity of biofilm formed on polystyrene. The extent of primary attachment to polystyrene as well as their capacity to form biofilm did not correlate with their cell surface hydrophobicity and exopolysaccharide production.
D-(+)-mannose inhibits biofilm formation by S. typhimurium DT104 on polystyrene but not on PVC. There was also a general lack of correlation between the ability of S. typhimurium DT104 to form biofilm and its physicochemical surface characteristics.
鼠伤寒沙门氏菌DT104菌株因其抗生素耐药性和广泛的宿主范围，已成为全球人类和兽医公共卫生关注的焦点。尽管人们认为它的毒性更强，但迄今为止，与其毒性相关的因素尚未完全阐明。因此，了解该菌株如何在疏水表面形成生物膜，将有助于增进我们对其可能的致病机制的现有认识。
通过在富含营养的生长培养基和各种调整后的培养基中生长后，从96孔组织培养板中回收的结晶紫结合细胞在600nm处的吸光度，以及基于标准程序的扫描电子显微镜，评估来自人和动物源的鼠伤寒沙门氏菌DT104临床分离株在疏水无生命表面上形成生物膜的能力。
在富含营养的生长培养基Luria-Bertani（LB）中，生物膜形成量较少，优先在聚苯乙烯上形成（p<0.05），且遵循不同的时间进程。当使用营养缺乏的生长培养基（粘附测试培养基）时，聚苯乙烯上形成的生物膜量显著降低。在LB中加入浓度为100mM的D-(+)-甘露糖可显著（p<0.05）抑制聚苯乙烯上的生物膜形成。D-(+)-葡萄糖相对增强了生物膜形成，但D-(-)-甘露醇对该过程的影响不显著。甘露糖对聚氯乙烯（PVC）的作用不显著，表明其作用可能依赖于表面。此外，葡萄糖分别显著降低了2株分离株以及仅在聚苯乙烯和PVC上的嗜PVC菌株T980021的生物膜生长。在所测试的浓度下，与木糖不同，D-甘露糖和D-葡萄糖均显著（p<0.05）抑制细菌生长，为它们对鼠伤寒沙门氏菌生物膜形成的抑制作用提供了一种可能的机制。虽然饥饿应激导致除嗜PVC菌株T980021外的所有菌株在聚苯乙烯上的生物膜形成显著减少，但高渗透压对聚苯乙烯上形成的生物膜量影响不大。对聚苯乙烯的初始附着程度及其形成生物膜的能力与其细胞表面疏水性和胞外多糖产生无关。
D-(+)-甘露糖抑制鼠伤寒沙门氏菌DT104在聚苯乙烯上形成生物膜，但对PVC无此作用。此外，鼠伤寒沙门氏菌DT104形成生物膜的能力与其物理化学表面特征之间普遍缺乏相关性。
