What is unique about Streptococcus pyogenes?

Streptococcus pyogenes (group A streptococcus; GAS) is unique among human pathogens in its ability to cause a wide variety of clinical infections and postinfectious sequelae. Further, in its coevolution with humans, GAS has developed a myriad of molecular strategies to circumvent important host defense mechanisms.

What are the cultural characteristics of Streptococcus pyogenes?

Cultural CharacteristicsNAM (Nutrient Agar Medium
ElevationLow Convex – convex
SurfaceMatt (in Virulent strains) ; Glossy (In Non-Virulent Strains) ; mucoid (in case of Capsule production)
ColorLight yellow
StructureSemi-Transparent – Opaque
9 may 2018

What is the morphology of Streptococcus pyogenes?

Streptococcus pyogenes is a Gram-positive, spherical, and facultative anaerobic bacterium. Similar in cellular morphology to Staphylococcus species, this species of bacteria grows in long chains versus the grape-like clusters observed as Staphylococcus.

What is the classification of Streptococcus pyogenes?

Bacilli is a taxonomic class of bacteria that includes two orders, Bacillales and Lactobacillales, which contain several well-known pathogens such as Bacillus anthracis. Bacilli are almost exclusively gram-positive bacteria.
The name Bacillus, capitalized and italicized, refers to a specific genus of bacteria.


How do you identify Streptococcus pyogenes?

To identify S. pyogenes in clinical samples, blood agar plates are screened for the presence of β-hemolytic colonies. The typical appearance of S. pyogenes colonies after 24 hours of incubation at 35-37°C is dome-shaped with a smooth or moist surface and clear margins.

Is Streptococcus pyogenes catalase positive or negative?

Streptococci are gram-positive, catalase-negative, coagulase-negative cocci that occur in pairs or chains. They are divided into three groups by the type of hemolysis on blood agar: beta-hemolytic (complete lysis of red cells), a hemolytic (green hemolysis), and gamma-hemolytic (no hemolysis).

What is Streptococcus pyogenes common name?

Streptococcus pyogenes, also known as the flesh eating bacteria, is the most pathogenic bacterium in the whole genus (2). The name pyogenes comes from the word pyogenic, which is a classification for the streptococci that are associated with pus formation.

What are the virulence factors of Streptococcus pyogenes?

GAS strains express many virulence factors including surface protein M, streptolysins, streptokinase, hyaluronidase, peptidoglycan, and teichoic acid. Protein M is considered as the main virulence factor, limiting phagocytosis, disturbing the function of complement, and being responsible for adhesion [4].

What type of hemolysis is Streptococcus pyogenes?

Streptococcus pyogenes are nearly always beta-hemolytic whereas closely related Groups B and C streptococci usually appear as beta hemolytic colonies, but different strains can vary in their hemolytic activity.

What are the cultural characteristics of Streptococcus?

Streptococci are Gram-positive, nonmotile, nonsporeforming, catalase-negative cocci that occur in pairs or chains. Older cultures may lose their Gram-positive character. Most streptococci are facultative anaerobes, and some are obligate (strict) anaerobes. Most require enriched media (blood agar).

What are the cultural characteristics of Staphylococcus?

Cultural characteristics of Staphylococcus aureus

Colonies on solid media are round, smooth, raised, and glistening. S. aureus usually forms gray to deep golden yellow colonies. Mannitol Salt Agar: circular, 2–3 mm in diameter, with a smooth, shiny surface; colonies appear opaque and are often pigmented golden yellow.

What are the characteristics of Streptococcus pneumoniae?

Streptococcus pneumoniae are lancet-shaped, gram-positive, facultative anaerobic bacteria with more than 100 known serotypes. Most S. pneumoniae serotypes can cause disease, but only a minority of serotypes produce the majority of pneumococcal infections.

What is the morphology of Streptococcus?

Morphology. Streptococci are coccoid bacterial cells microscopically, and stain purple (Gram-positive) when Gram staining technique is applied. They are nonmotile and non-spore forming. These cocci measure between 0.5 and 2 μm in diameter.

What are identifying characteristics of Staphylococcus aureus?

S. aureus cells are Gram-positive and appear in spherical shape. They are often in clusters resembling bunch of grapes when observed under light microscope after Gram staining. The name ‘Staphylococcus’ was derived from Greek, meaning bunch of grapes ( staphyle ) and berry ( kokkos ) [1].

What is the Colour of Staphylococcus?


On blood agar, S. aureus usually displays a light to golden yellow pigment, whereas S. epidermidis has a white pigment and S. saprophyticus either a bright yellow or white pigment.

What are the biochemical characteristics of Staphylococcus aureus?

The species is identified on the basis of a variety of conventional physiological or biochemical characters. The key characters for Staphylococcus aureus are colony pigment, free coagulase, clumping factor, protein A, heat-stable nuclease, lipase, and acid production from mannitol [1].

How do you differentiate between Staphylococcus and Streptococcus?

Staphylococci and Streptococci are grouped as Gram-positive cocci. Staphylococci form clumps, whereas Streptococci grow in chains. They can be discriminated by catalase test because Staphylococci have the capability to produce catalase [2].

What is one way you can distinguish between a Streptococcus and a Staphylococcus infection?

The catalase test is important in distinguishing streptococci (catalase-negative) staphylococci which are catalase positive.

What test can differentiate the three major species of Staphylococcus?

Coagulase test

S. aureus is differentiated from other staphylococci by the coagulase test. However it is now known that not all S. aureus are coagulase positive and not all coagulase positive staphylococci are S.

What is the difference between Streptococcus pyogenes and Staphylococcus aureus?

Although all infections are potentially serious, the microbiological literature associates Staph. aureus rather with localized disease such as abscess formation and purulent discharge, while Strep. pyogenes is linked to extensive diseases ranging from erysipelas to necrotizing fasciitis [1–4.

What are 3 good ways to differentiate Staphylococcus and Streptococcus?

Staph does not need enriched media (not fastidious). Strep needs enriched media (fastidious). Staphylococci are found on the skin. Streptococci are found in the respiratory tract.

What is the best test to differentiate between the genus Staphylococcus and Streptococcus?

The catalase test is a particularly important test used to determine whether the Gram + cocci is a staphylococci or a streptococci. Catalase is an enzyme that converts hydrogen peroxide to water and oxygen gas.

What do S. aureus and S pyogenes have in common?

Both Staphylococcus aureus and Streptococcus pyogenes (group A strep) have many enzymes which act as virulence factors allowing these bacteria to invade tissue from patients with normal immunity and spread from infection at a local site to the bloodstream.