The purpose of this study is to determine whether daily treatment with Streptococcus Salivarius BLIS K-12 prevents streptococcal throat infection in children that have had an episode of rheumatic fever.

Children diagnosed with Rheumatic fever are currently given preventive streptococcal treatment with either monthly IM (intramuscular injection) Penicillin or daily oral Penicillin.

This preventive treatment is recommended for years until the child is 20 y old or even later. The compliance rate for this treatment declines significantly with time (the injections are painful) and even with good adherence the prevention is not complete.

In the last few years a new product licensed as "BLIS K-12" has been developed and approved by FDA as GRAS (generally recognized as safe) status from 2011.

This probiotic treatment prevents the pathogenic Strep A from adhering to the throat of the child thus preventing the infection. This kind of prevention is better for the long run for the patient and for the surrounding, It is better tolerated, is effective even if a dose is skipped or missed is not painful and is tasty to the children.

So the investigators assumption is that giving this product to children instead of Penicillin either orally or intramuscularlly will be better tolerated thus give a better protection profile with much less side effects.

The investigators will be giving BLIS K-12 to those children on the trial on a daily basis for 6 autumn-winter months instead of Penicillin and will monitor the children by monthly throat swabs. The investigators will also obtain Anti Streptolysin blood test at the end of the period from all participants to evaluate possible Strep encounters.

Inclusion Criteria:

• Rheumatic heart disease with recommended strep prophylaxis

Exclusion Criteria:

• less than one year from first diagnosis
• refusal to take the tablets