EMBRAPA Agroindustria de Alimentos, Rio de Janeiro, RJ, Brazil.
EMBRAPA Caprinos e Ovinos, Sobral, CE, Brazil.
Probiotics Antimicrob Proteins. 2020 Dec;12(4):1524-1541. doi: 10.1007/s12602-020-09637-8.
The genus Streptococcus includes various species, remarkably different in their behavior, applications, virulence, and safety. Taxonomically Streptococcus infantarius subsp. infantarius belonging to the Streptococcus bovis group, which includes several pathogen species, however, has been found as predominant species in some African dairy products that are widely consumed and considered to be safe. Streptococcus infantarius subsp. infantarius' safety may be questioned due to the association of this species with clinical cases. In this study, isolates from dairy origin were selected based on their bacteriocinogenic potential and differentiated by their RAPD-PCR profiles. Two strains were identified by 16S rRNA sequencing as St. infantarius subsp. infantarius and investigated regarding their potential beneficial properties and factors related to virulence and safety. A series of in vitro tests included properties related to survival in the gastrointestinal tract and beneficial intestinal activities. Production of bacteriocin/s, detection of related genes, and partial characterization of expressed antimicrobial protein were evaluated. Genes related to folate biosynthesis were detected in both studied strains. Evaluation of physiological tests related to strains virulence, adhesion, and resistance to antibiotics and detections of virulence and biogenic amines production-related genes were also investigated. Taking in consideration all the aspects of the specific nature of St. infantarius subsp. infantarius K1-4 and K5-1 (beneficial properties and virulence characteristics), both strains cannot be considered safe for human or other animals application, even though they have been isolated from dairy products. This study is highlighting the importance of evaluation for presence of potential virulence factors in newly characterized strains in order to be confident in their safety.
链球菌属包括多种在行为、应用、毒力和安全性方面差异显著的物种。在分类学上，婴儿链球菌亚种属于牛链球菌群，该群包括几个病原体物种，但在一些非洲乳制品中被发现为主要物种，这些乳制品广泛食用，被认为是安全的。由于该物种与临床病例有关，因此婴儿链球菌亚种的安全性可能受到质疑。在这项研究中，根据其细菌素产生潜力从乳制品来源中选择分离株，并通过 RAPD-PCR 图谱进行区分。通过 16S rRNA 测序鉴定出两种菌株为婴儿链球菌亚种，并研究了它们的潜在有益特性以及与毒力和安全性相关的因素。一系列体外试验包括与胃肠道生存和有益肠道活性相关的特性。评估了细菌素/ s 的产生、相关基因的检测以及表达抗菌蛋白的部分特性。在两种研究菌株中都检测到与叶酸生物合成相关的基因。还评估了与菌株毒力、粘附和抗生素抗性相关的生理试验，并检测了与毒力和生物胺产生相关的基因。考虑到婴儿链球菌亚种 K1-4 和 K5-1 的特定性质的所有方面（有益特性和毒力特性），即使它们是从乳制品中分离出来的，这两种菌株也不能被认为对人类或其他动物的应用是安全的。本研究强调了在对新鉴定的菌株进行潜在毒力因子存在评估的重要性，以确保其安全性。
