Internalization–associated proteins among Streptococcus pyogenes isolated from asymptomatic carriers and children with pharyngitis

Sixty-two strains of Streptococcus pyogenes isolated from 30 asymptomatic school children and 32 children with pharyngitis were characterized to analyze the involvement of 2 fibronectin-binding proteins (F/SfbI and PrtF2/PfbpI) in S. pyogenes colonizing asymptomatic carriers and to determine the possible association between these proteins and the genes associated with macrolide resistance. In this study, we demonstrated that the proportion of S. pyogenes strains carrying the pfbpI gene was significantly higher among asymptomatic carriers (80%) than among children with pharyngitis (53%; P<.05). With regard to the proportion of prtF1-positive strains, no significant differences were found between the 2 groups (70% vs. 69%, for asymptomatic carriers and children with pharyngitis, respectively). Another important finding is the significant association between macrolide resistance and protein F/SfbI (P<.001) in both groups. These results suggest that the presence of the pfbpI gene can be linked to the ability of S. pyogenes to persist in the throat of asymptomatic carriers.