Pharyngitis is inflammation of the pharynx. It is also known as “sore throat”. This infection may be acute or chronic. Most cases are caused by viruses but it can also be caused by bacteria. Clinically, it is difficult to differentiate between bacterial and viral cause of pharyngitis based on symptoms alone. 

The most common cause of bacterial pharyngitis is the Lancefield Group A, Streptococcus (S. pyogenes).

Diphtheria is an acute infectious disease of the upper respiratory tract and occasionally the skin. It is caused by toxigenic strains of Corynebacterium diphtheriae (of which there are 4 biotypes - gravis, mitis, intermedius and belfanti) and some toxigenic strains of Corynebacterium ulcerans and Corynebacterium pseudotuberculosis

Vincent’s angina Borrelia vincentii and Fusobacterium species are associated with the infection known as Vincent's angina.

Fusobacterium necrophorum infection may be characterised by acute pharyngitis and fever, sometimes accompanied by membranous tonsillitis. In the absence of therapy, a small number of these patients may develop bacteraemia and metastatic infection characteristic of Lemièrre’s disease, which can be life threatening