Recurrent Group A Streptococcus (GAS) infections, primarily presenting as strep throat, are a significant health concern in pediatric populations, leading to symptoms like sore throat, fever, and swollen lymph nodes. GAS is highly contagious and can spread easily among children in close-contact environments like schools and daycare centers, often resulting in frequent re-infections. Managing these recurrent infections typically requires antibiotics, but reliance on antibiotics carries risks, including resistance development, gut microbiota disruption, and various side effects. Probiotic therapy, particularly with Streptococcus salivarius K12, has shown promise as a preventive approach, utilizing competitive exclusion and antimicrobial production to inhibit GAS growth in the oral cavity. Recent studies have advanced this with the development of S. salivarius eK12, a re-engineered strain that enhances efficacy against GAS by preventing the survival-promoting interactions between the probiotic and pathogenic bacteria. This modified strain, now registered as Bactoblis® EVOL in Italy (EU), holds potential as an effective version to reduce the incidence and severity of GAS infections without the drawbacks of antibiotic therapy.

The primary aim of this clinical trial is to evaluate whether prophylactic use of S. salivarius eK12 can effectively reduce the frequency and severity of strep throat episodes in children. By assessing the efficacy of S. salivarius eK12 supplementation, this study seeks to provide insights into its potential as a non-antibiotic preventive strategy for recurrent strep throat infections in pediatric populations.

Inclusion Criteria:

• Children aged 3-10 years.
• Recent history of documented recurrent episodes of Streptococcus pyogenes pharyngo- tonsillitis infection in the last 6 months, or 4 or more episodes in the last 12 months (S.

pyogenes infection being defined as: McIsaac score with clinical score ≥ 2 plus confirmation of S. pyogenes presence with rapid throat swab (RAD) method or McIsaac score =5.

• Willingness to comply with the study protocol and attend scheduled follow-up visits.
• Written informed consent obtained from the parent or legal guardian.

Exclusion Criteria:

• Children with known allergies or hypersensitivity to probiotics or any components of the study product.
• Current use of antibiotics or within the past 30 days.
• Used oral colonizing probiotics in the last 6 months.
• Presence of severe underlying medical conditions affecting the immune system or gastrointestinal tract.
• Participation in other clinical trials involving investigational drugs or interventions.
• Inability to adhere to the study requirements due to logistical or social reasons.
• History of rheumatic disorders, bronchospasm, severe asthma, or allergy requiring corticosteroids.
• Past tonsillectomy or an indication for adeno-tonsillectomy; or severe respiratory or systemic disorders
• Individuals immunocompromised or had a condition favouring recurrent Acute Otitis Media (AOM), including severe atopy, acquired or congenital immunodeficiency, cleft palate, craniofacial abnormalities, obstructive adenoids, a chronically ruptured eardrum, sleep apnoea, or tympanostomy tubes
• Children undergoing current pharmacological therapies to prevent recurrent respiratory infections.
• Any other medical condition or circumstance that, in the investigator's judgment, would compromise the safety of the participant or the integrity of the study.