Abstract
Streptococcus pyogenes and Streptococcus pneumoniae, representative Gram-positive cocci, may cause both localized (skin and soft tissue) and systemic infections. Lobar pneumonia is a unique form of acute and severe lung infection of S. pneumoniae. Streptococcus viridans group, normal flora of the oral cavity, may lead not only to mucosal infection but also to aspiration pneumonia, infective endocarditis, and systemic infections. The severest and often lethal form of progressive and systemic infection includes fulminant streptococcal and pneumococcal infections. Autopsy is essentially important for the analysis of fulminant infections. Pathological features of varied streptococcal infections are illustrated and discussed. Immunohistochemical identification of the pathogen in formalin-fixed, paraffin-embedded sections is effective and valuable in confirming the type of infected pathogens.