What is the Lancefield system classification of streptococci?

What is the Lancefield system classification of streptococci?

Lancefield grouping is a serological method for classifying streptococci into one of 20 groups (designated by a letter) based on the presence of polysaccharide and teichoic acid antigens in the bacterial cell wall (Lancefield 1933).

What is the morphology of Streptococcus bacteria?

Morphology: Spherical, ovoid, or cocci shaped. Often occur in pairs or chains when grown in liquid media.

What is the Lancefield classification based on?

Lancefield grouping is a system of classification that classifies catalase-negative Gram-positive cocci based on the carbohydrate composition of bacterial antigens found on their cell walls.

What is the morphology of Streptococcus pyogenes?

They display a white-greyish color and have a diameter of > 0.5 mm, and are surrounded by a zone of β-hemolysis that is often two to four times as large as the colony diameter. Microscopically, S. pyogenes appears as Gram-positive cocci, arranged in chains (Figure 1).

What shape is Streptococcus pneumoniae?

Streptococcus pneumoniae are lancet-shaped, gram-positive, facultative anaerobic bacteria with more than 100 known serotypes.

What is the meaning of Lancefield?

Medical Definition of Lancefield group : any of the serologically distinguishable groups into which most streptococci can be divided and which are based on the polysaccharide antigens present in the streptococcal cell walls — see group a, group b.

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 classification of Streptococcus pyogenes?

Streptococcus pyogenes is a gram-positive bacterium that usually grows in pairs or chains. It has been classified as a beta-hemolytic streptococcus because when cultured on a blood agar plate all the red blood cells are ruptured by the bacteria (1).

Is strep pneumoniae Group A or B?

Group B (GBS) streptococcal pneumonia is the most common type of pneumonia in neonates. The infection is acquired during birth, and at least 25% of women in labor are colonized by the organism. Premature infants are more commonly infected than are term infants.

Is group B strep Gram-positive or negative?

Group B Strep are Gram-positive cocci in pairs and short chains on Gram stain. The most accurate way to identify group B Streptococcus (GBS) is to demonstrate that the bacteria in question has the Lancefield group B antigen on the surface of the bacteria.

What is Lancefield classification in microbiology?

Lancefield classification (lans-feeld) n. a classification of the Streptococcus bacteria based on the presence or absence of antigenic carbohydrate on the cell surface. Species are classified into the groups A–S. Most species causing disease in humans belong to groups A, B, and D. [

Is Streptococcus pneumoniae rod shaped?

Summary. Streptococcus pneumoniae is an oval-shaped Gram-positive coccus that lives in intimate association with its human host, both as a commensal and pathogen.

What is morphology and arrangement?

While arrangement refers to the groupings of individual cells, morphology describes the appearance of groups of bacteria, or colonies. Colony shapes can be round, irregular, filamentous or curled. Colonies might be flat or have a rounded elevation.

What is the colony morphology of Streptococcus pneumoniae?

COLONY MORPHOLOGY: Pneumococci produce pneumolysin, which breaks down hemoglobin into a green pigment that can be observed as a large green zone surrounding S. pneumoniae colonies growing on blood-agar plates.

How is S. pneumoniae distinguished from other streptococci with the same hemolytic properties?

Bile solubility testThe bile (sodium deoxycholate) solubility test distinguishes S. pneumoniae from all other alpha-hemolytic streptococci. S. pneumoniae is bile soluble whereas all other alpha-hemolytic streptococci are bile resistant.