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.

属链球菌包括不同种类，他们的行为，应用程序，毒力和安全性显着不同。分类学上的婴儿链球菌亚种。但是，在一些非洲乳制品中，牛乳链球菌属于婴儿链球菌，其中包括几种病原体，已被发现为主要菌种，被认为是安全的。婴儿链球菌亚种。婴儿由于该物种与临床病例的关系，安全性可能受到质疑。在这项研究中，根据其细菌致癌潜力选择了乳制品来源的分离株，并通过其RAPD-PCR谱进行了区分。通过16S rRNA测序鉴定了两个菌株为婴儿链球菌亚种。婴儿并调查了它们的潜在有益特性以及与毒力和安全性有关的因素。一系列体外试验包括与胃肠道存活和有益的肠活动有关的特性。评价了细菌素的产生，相关基因的检测以及表达的抗菌蛋白的部分表征。在两个研究菌株中均检测到与叶酸生物合成有关的基因。还评估了与菌株毒力，粘附力和对抗生素的抗性相关的生理测试以及毒力和生物胺生产相关基因的检测。考虑到所有的方面的圣婴子亚种的具体性质。婴儿K1–4和K5–1（有益特性和毒力特性），即使它们已从乳制品中分离出来，也不能认为对人或其他动物而言都是安全的。这项研究突出了评估新特性菌株中潜在毒力因子的存在的重要性，以便对其安全性充满信心。