Streptococcus salivarius as a donor or recipient organism for genetic engineering

Streptococcus salivarius is one of the Lactic acid bacteria , the representatives of the species are Gram-positive, facultatively anaerobic, immobile, catalase-negative and non-spore-forming cocci. The bacterium belongs to the first colonizers or commensals of the oral mucosa and is one of the dominant types of biofilm on the upper surface of the tongue. In addition to the oral cavity, S. salivarius can also colonize the upper respiratory tract, the intestines, and rarely other organs. S. salivarius occurs primarily in humans, but has also been detected in the oral cavity of chimpanzees and dairy cows.

S. salivarius is facultatively pathogenic and can cause endogenous or nosocomial infections in humans, especially in immunocompromised individuals. S. salivarius is transmitted via droplet infection or in the context of medical procedures (e.g., after spinal surgery or dental treatment). Specific pathogenicity factors have not yet been identified in S. salivarius However, the genomes of different isolates contain genes for different antibiotic resistances. Since some of these isolates also carry mobile genetic elements, this suggests a potential transferability of antibiotic resistance genes through horizontal gene transfer. Many S. salivarius strains encode large extrachromosomal DNA molecules, so-called megaplasmids. Bacteriocins , which are antibiotic proteins directed against similar bacteria. Currently, two bacteriocin-producing strains, S. salivarius K12 and M18, are considered probiotic dietary supplement commercially distributed. There is no evidence of pathogenicity for either strain, and human consumption is considered safe.

Also the p. salivarius strains 24SMB and DB-B5 were investigated in clinical studies for their suitability as probiotics. In previously conducted safety analyses, no virulence or antibiotic resistance genes could be detected in these two S. salivarius strains. In the Technical Rules for Biological Agents 466 "Classification of Prokaryotes (Bacteria and Archaea)", S. salivarius is assigned to risk group 2 with the designation "TA" ("long-term safe in technical application"), whereby the designation "TA" refers to the S. salivarius strains K12 and M18. The ZKBS classifies the S. salivarius strains K12, M18, 24SMB and DB-B5 according to Section 5 Paragraph 1 GenTSV in conjunction with the criteria in Annex 1 GenTSV as donor and recipient organisms for genetic engineering work in the Risk group 1 a. All other S. salivarius strains and isolates are Risk group 2 The reasoning states that S. salivarius is ubiquitous and naturally occurs mainly in the human oral cavity. S. salivarius strains K12, M18, 24SMB, and DB-B5 are well characterized, and there is no evidence of a potential risk to humans, animals, or the environment. For other S. salivarius strains, a low risk to humans and animals cannot be ruled out. The current ZKBS statement on S. salivarius can be found at File number 45241.0229 can be retrieved.