1. The use of strain Lactobacillus casei to obtain a composition for the treatment or prevention of common respiratory infections in a tobacco smoker. ! 2. The use according to claim 1, where the specified tobacco smoker is younger than 65 years. ! 3. The use of the strain Lactobacillus casei to obtain a composition for stimulating the response of natural killer cells in an individual with a common respiratory infectious disease. ! 4. The use according to claim 3, where the specified individual is younger than 65 years. ! 5. The use according to any one of claims 1 to 4, where the specified common respiratory infectious disease is rhinopharyngitis or laryngitis. ! 6. The use according to any one of claims 1 to 4, where the specified strain of Lactobacillus easel is a strain of Lactobacillus casei ssp. paracasei. ! 7. The use according to claim 5, where the specified strain of Lactobacillus casei is a strain of Lactobacillus casei ssp. paracasei. ! 8. The use according to claim 6, where the specified strain of Lactobacillus paracasei is a strain deposited in CNCM under the number I-1518. ! 9. The use according to claim 7, where the specified strain of Lactobacillus paracasei is a strain deposited in CNCM under the number I-1518. ! 10. The use according to any one of claims 1 to 4, where the specified composition contains at least 1 × 105 CFU per milliliter of the specified strain of Lactobacillus easel. ! 11. The use of claim 10, where the specified composition contains at least 1 × 107 CFU per milliliter of the specified strain of Lactobacillus casei. ! 12. The use according to any one of claims 1 to 4, where the composition further comprises at least one genus of bacteria selected from the genera Lactobacillus, Lactococcus, Streptococcus and Bifidobacterium. ! 13. The use according to claim 5, where the composition further comprises at least one genus of bacteria selected from the genera Lactobacillus, Lactococcus, Streptococcus and Bifidobacterium. ! 14. The appli
