Pneumococcus vs Viridans streptococci- 12 Major Differences


Streptococcus pneumoniae and Viridans streptococci are two groups of gram-positive bacteria that belong to the genus Streptococcus. They are both spherical or ovoid in shape and form chains or pairs when they grow. They are also both facultative anaerobes, meaning they can grow with or without oxygen. However, they have different characteristics and roles in human health and disease.

Streptococcus pneumoniae, also known as pneumococcus, is a major cause of pneumonia, meningitis, otitis media, sinusitis, and septicemia. It is one of the most common bacterial pathogens in humans and can affect people of all ages. It has a polysaccharide capsule that protects it from phagocytosis and helps it adhere to host cells. It also produces several virulence factors, such as pneumolysin, autolysin, and hydrogen peroxide, that damage host tissues and immune cells. It is classified into more than 90 serotypes based on the antigenic variation of its capsule.

Viridans streptococci are a heterogeneous group of streptococci that are normally found in the oral cavity, gastrointestinal tract, genitourinary tract, and skin of humans. They are usually harmless commensals that do not cause disease in healthy individuals. However, they can become opportunistic pathogens when they enter the bloodstream or other sterile sites, especially in immunocompromised or debilitated patients. They can cause endocarditis, bacteremia, abscesses, and dental caries. They are classified into six groups based on their biochemical and phenotypic properties: anginosus group, mitis group, mutants group, salivarius group, bovis group, and sanguinis group.

In this article, we will compare and contrast the properties of Streptococcus pneumoniae and Viridans streptococci and highlight the 12 major differences between them.