Antimicrobial susceptibility and Beta-lactamase production of anaerobic and aerobic bacteria isolated from pus specimens from orofacial infections

Sixty-two strains of Streptococcus pyogenes isolated from 30 asymptomatic school children and 32 childrenwith pharyngitis were characterized to analyze the involvement of 2 fibronectin-binding proteins (F/SfbI andPrtF2/PfbpI) in S. pyogenes colonizing asymptomatic carriers and to determine the possible association betweenthese proteins and the genes associated with macrolide resistance. In this study, we demonstrated that theproportion 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-positivestrains, no significant differences were found between the 2 groups (70% vs. 69%, for asymptomatic carriersand children with pharyngitis, respectively). Another important finding is the significant association betweenmacrolide resistance and protein F/SfbI (P ! .001) in both groups. These results suggest that the presence ofthe pfbpI gene can be linked to the ability of S. pyogenes to persist in the throat of asymptomatic carriers.