Fig. 1.

Analysis of bacteria isolated from recurrently infected tonsils of psoriasis patients and controls revealed that tonsils from psoriasis patients were infected more frequently by β-haemolytic Streptococci. Psoriasis tonsils (PST, left) were infected more frequently by β-haemolytic Streptococci than were the recurrently infected tonsils not associated with skin disease (RT, right, P = 0·021), with a strong bias towards Streptococcus C infection (P = 0·036). Two distinct bacterial species could be cultured from some of the tonsils, and this occurred significantly more frequently with PST tonsils (P = 0·001). In terms of co-infections, the co-culture of Streptococcus G and C was the only common factor between the two tonsil groups. No difference was observed in the overall number of uninfected tonsils [32% in PST versus 56% in recurrently infected tonsils (RT)]. Infections by bacterial species other than streptococcus were more frequent among the psoriasis tonsils (six of 25 versus two of 41, P = 0·0455). Fisher's exact test, two-tailed P-values.