Streptococcus pyogenes (Group A Streptococcu)s is the etiologic agent responsible for many conditions related to streptococcal infections. It is more commonly known as Group A Strep and has more than 6,000 recognized subtypes, with new strains constantly arising. The most common form of infection involves a colonization of the pharyrix known as strep throat. cause pharyngitis, scarlet fever, and toxic shock. 

Biochemical and Morphological Characteristics

They tend to be short chains in clinical samples with longer chains in liquid media. They are beta hemolytic and contain an outer capsule. In the pre-antibiotic era severe infections due to group A ß-haemolytic streptococcus were major causes of morbidity and mortality. 

Diagnosis and Symptoms 

The clinical features of group A sreptococcal pneumonia include sudden high fever, pleuritic chest pain, chills, caugh, sputum and dyspnoea. The most typical feature suggesting the diagnosis of group A streptococcal pneumonia is the rapid accumulation of a plueral effusion. In view of the emergence of more virulent group A streptococcal infections, it is important to initiate early and appropriate antibiotic therapy for common uncomplicated streptococcal infections such as pharyngitis, tonsillitis, impetigo and cellulitis.

Mechanisms of pathology:

Secretion of Enzymes:

–Endoglycosidases: S. pyogenes secretes two enzymes shwoing remarkable specificity for IgG; EndoS and IdeS. 

(i) EndoS efficiently and specifically hydrolyzes the functionally important N-linked glycan of IgG and treatment with EndoS abrogates the pathogenic activity of IgG in mouse models of autoimmune disease.

 (ii) IdeS or streptococcal Mac-1 is a secreted cysteine proteinase that specifically cleaves the heavy chain of IgG. Due to its early and sustained expression during growth and its highly specific proteolytic activity, IdeS is a tailor-made defense against Fc mediated phagocytic killing. In one study, the enzyme was found to block the development of IgG-induced arthritis. Johansson (“IdeS: a bacterial proteolytic enzyme with therapeutic potential” 2008) showed that this enzyme in vitro efficiently cleaves IgG in human whole blood, removes IgG from the blood circulation of rabbits without any side effices and cures mice from lethal IgG induced thrombocytopenia.