Are pneumococci alpha-hemolytic?
ABSTRACT. Streptococcus pneumoniae and other streptococci produce a greenish halo on blood agar plates referred to as alpha-hemolysis.
What type of hemolysis is produced by Streptococcus viridans?
The viridans streptococci are a large group of commensal streptococcal Gram-positive bacteria species that are α-hemolytic, producing a green coloration on blood agar plates (hence the name “viridans”, from Latin “vĭrĭdis”, green), although some species in this group are actually γ-hemolytic, meaning they produce no …
What part of the pneumococcus is responsible for the bacteria’s pathogenicity?
The cell wall of pneumococci is a major determinant of the course of disease. The interaction of PCho on the cell wall teichoic acid binds to PAFr and enables bacterial invasion of cells and transmigration across barriers.
What is the principle of optochin test?
Principle of Optochin Susceptibility Test The chemical tests the fragility of the bacterial cell membrane and causes S. pneumoniae to lyse due to changes in surface tension.
What does strep viridans cause?
Viridans streptococci, a diverse group of streptococcal species, are important causes of sepsis and pneumonia in the neutropenic host and sepsis and meningitis in the neonate. The oral mucosa is the most common portal of entry.
What is the function of pneumolysin?
Pneumolysin is a cholesterol-dependent cytolysin (CDC) toxin that forms lytic pores in host membranes and mediates pneumococcal disease pathogenesis by modulating inflammatory responses.
What is the morphology of pneumococcus?
Morphology. Streptococcus pneumoniae is a Gram-positive, non-motile, non-spore-forming bacterium [2]. S. pneumoniae cells appear as lance-shaped cocci and typically form in pairs (diplococci) but can also appear as single cocci or cocci chains [2,3].
What is the transforming principle in microbiology?
In the early 1940s, they began a concerted effort to purify the “transforming principle” and understand its chemical nature. Bacteriologists suspected the transforming factor was some kind of protein. The transforming principle could be precipitated with alcohol, which showed that it was not a carbohydrate like the polysaccharide coat itself.
What was the original name of the transforming principle?
See additional information. Transforming principle: Name originally given to DNA. In 1944 Avery, MacLeod, and McCarty published their discovery that the transforming principle was DNA.
What happened to the transforming principle of polysaccharides?
The transforming principle could be precipitated with alcohol, which showed that it was not a carbohydrate like the polysaccharide coat itself. But Avery and McCarty observed that proteases – enzymes that degrade proteins – did not destroy the transforming principle.