LeBel Geneviève, Vaillancourt Katy, Frenette Michel, Gottschalk Marcelo, Grenier Daniel
Groupe de Recherche en Écologie Buccale, Faculté de Médecine Dentaire, Université Laval, Quebec City, Quebec, Canada.
Groupe de Recherche en Écologie Buccale, Faculté de Médecine Dentaire, Université Laval, Quebec City, Quebec, Canada Centre de Recherche en Infectiologie Porcine et Avicole, Fonds de Recherche du Québec-Nature et Technologies, Quebec City, Quebec, Canada.
Appl Environ Microbiol. 2014 Sep;80(17):5484-92. doi: 10.1128/AEM.01055-14. Epub 2014 Jun 27.
Streptococcus suis serotype 2 is known to cause severe infections (meningitis, endocarditis, and septicemia) in pigs and is considered an emerging zoonotic agent. Antibiotics have long been used in the swine industry for disease treatment/prevention and growth promoters. This pattern of utilization resulted in the spread of antibiotic resistance in S. suis worldwide. Interestingly, pigs may harbor S. suis in their tonsils without developing diseases, while North American strains belonging to the sequence type 28 (ST28) are nonvirulent in animal models. Consequently, the aim of this study was to purify and characterize a bacteriocin produced by a nonvirulent strain of S. suis serotype 2, with a view to a potential therapeutic and preventive application. S. suis 90-1330 belonging to ST28 and previously shown to be nonvirulent in an animal model exhibited antibacterial activity toward all S. suis pathogenic isolates tested. The bacteriocin produced by this strain was purified to homogeneity by cationic exchange and reversed-phase fast protein liquid chromatography. Given its properties (molecular mass of <4 kDa, heat, pH and protease stability, and the presence of modified amino acids), the bacteriocin, named suicin 90-1330, belongs to the lantibiotic class. Using a DNA-binding fluorophore, the bacteriocin was found to possess a membrane permeabilization activity. When tested on other swine pathogens, the suicin showed activity against Staphylococcus hyicus and Staphylococcus aureus, whereas it was inactive against all Gram-negative bacteria tested. Amino acid sequencing of the purified bacteriocin showed homology (90.9% identity) with nisin U produced by Streptococcus uberis. The putative gene cluster involved in suicin production was amplified by PCR and sequence analysis revealed the presence of 11 open reading frames, including the structural gene and those required for the modification of amino acids, export, regulation, and immunity. Further studies will evaluate the ability of suicin 90-1330 or the producing strain to prevent experimental S. suis infections in pigs.
猪链球菌2型已知会在猪身上引发严重感染（脑膜炎、心内膜炎和败血症），并被视为一种新出现的人畜共患病原体。抗生素长期以来在养猪业中用于疾病治疗/预防以及作为生长促进剂。这种使用模式导致猪链球菌的抗生素耐药性在全球范围内传播。有趣的是，猪的扁桃体中可能携带猪链球菌但不发病，而属于序列型28（ST28）的北美菌株在动物模型中无致病性。因此，本研究的目的是纯化并表征由猪链球菌2型无毒菌株产生的一种细菌素，以期用于潜在的治疗和预防应用。属于ST28且先前在动物模型中显示无致病性的猪链球菌90 - 1330对所有测试的猪链球菌致病分离株均表现出抗菌活性。该菌株产生的细菌素通过阳离子交换和反相快速蛋白质液相色谱法纯化至同质。鉴于其特性（分子量小于4 kDa、热稳定性、pH稳定性和蛋白酶稳定性以及存在修饰氨基酸），这种名为suicin 90 - 1330的细菌素属于羊毛硫抗生素类。使用一种DNA结合荧光团，发现该细菌素具有膜通透化活性。在对其他猪病原体进行测试时，suicin对猪葡萄球菌和金黄色葡萄球菌有活性，而对所有测试的革兰氏阴性菌无活性。纯化细菌素的氨基酸测序显示与乳房链球菌产生的乳链菌肽U具有同源性（90.9%的同一性）。通过PCR扩增了参与suicin产生的假定基因簇，序列分析揭示存在11个开放阅读框，包括结构基因以及氨基酸修饰、输出、调控和免疫所需的基因。进一步的研究将评估suicin 90 - 1330或产生菌株预防猪实验性猪链球菌感染的能力。
