The neutral outcome of the recently reported school-based trial of probiotic K12 (The effect of the oral probiotic Streptococcus salivarius K12 on group A streptococcus pharyngitis: a pragmatic trial in schools) can be attributed at least partially to several readily identifiable confounding factors. Mainly, the execution and outcome were negatively impacted by (a) the suboptimal efficacy and frequency of K12 administration, (b) the failure both clinically and microbiologically to adequately diagnose and distinguish active group A streptococci (GAS) pharyngitis from harmless GAS carriage, and (c) the exceptionally low occurrence of GAS in this population at the time of the probiotic intervention due to recent high-intensity antibiotic exposure.
Keywords: Carriage; Group A streptococci; Oral probiotic; Pharyngitis; Streptococcus salivarius K12.