The aim of this study was to examine effectiveness of oral probiotic Streptococcus salivarius K12 in preventing group A streptococcus pharyngitis in 5- to 14-year-old children at high risk of acute rheumatic fever. New Zealand has high rates of acute rheumatic fever among Māori and Pacific children. Children were already enrolled in a school-based Ministry of Health throat swabbing and treatment program. Children self-identified and reported sore throats daily and were swabbed twice weekly.
A total of 1314 children were quasirandomized (based on odd or even birthdates) to receive either K12 (2.5 × 10(9) cfu per lozenge) or placebo lozenges and continued observed daily treatment (in the school week, during school time) for one school year.
A total of 801 children (61.0%) reported a sore throat on one or more occasions resulting in 2927 pharyngeal swabs. Of these swabs, 1525 (52.1%) were taken from 411 children receiving K12 and 119 (7.8%) of these were positive for group A streptococcus on routine culture. In addition, 1402 (47.8%) swabs were taken from 390 children receiving placebo and 124 (8.8%) were positive. Overall there was a nonsignificant 11.2% relative reduction in positive swabs among children receiving K12. This relative reduction was greater for older children, 7-9 years of age, 15.6%, and for children 10 years and older, 30.2%.
S. salivarius K12 had modest nonsignificant effects on culture-positive sore throats when given at school, during the school day. Based on our pragmatic trial, the routine use of this probiotic in the prevention of pharyngitis associated with GAS detection is not supported.