Color-enhanced SEM of bacteria present in the pus in the crypts of adult tonsils, which may cause "strep throat." This includes Streptococcus pyogenes - beta-hemolytic Streptococcus Group A. This pathogen is present in 90% of all cases of pharyngitis (inflammation of the pharynx), but pus on the tonsils is not a sign of bacterial infection. Tonsillitis is part of pharyngitis. Solid yellow pus may develop on the tonsils of otherwise healthy adults. It may be squeezed out in the form of small lumps. When fixed, the pus reveals its bacterial composition under a scanning electron microscope. Although it is usually not associated with strep throat, group A strep can also produce a "necrotizing fasciitis" (the infamous "flesh-eating bacteria"). Image width: 9.85 micrometers. Magnification: 10,150x if the image is printed 10 cm wide.