Remarkable attachment of lactoferrin to Streptococcus pyogenes during acute pharyngotonsillitis

The purpose of this study was to establish whether lactoferrin (hLf) attached to Streptococcus pyogenes, one causative agent of acute pharyngotonsillitis (AT), during the course of the disease. Bacterial samples were obtained from the tonsillar surfaces of 7 patients (6 females, 1 male; median age 26 years; range 16-50 years) suffering from AT who were culture-positive for S. pyogenes and from 5 healthy adult controls who were culture-negative for this pathogen. Using gold-labelled antiserum against S. pyogenes and hLf, this pathogen and other bacteria on the tonsillar surfaces coated with hLf could be identified by tracing the gold particles in a transmission electron microscope. In healthy adults, 8% (median value; range 6-12%) of the surface tonsillar bacteria were coated with hLf. In AT patients, 59% (median value; range 42 67%) of S. pyogenes were coated with hLf, in contrast to 9% (median value; range 0-26%) of all other bacteria (p < 0.01). This study hints that hLf might participate in recovery from AT in several ways, e.g. by binding to the S. pyogenes pathogens, in addition to its well-known virtue of iron-binding capacity.