Streptococci Flashcards
How are Streptococci categorized?
By Lancefield Groups based on carbohydrate types
The groups include A, B, C, D, pneumococci, and viridans.
What is the primary method used to type Streptococci?
Blood agar to determine beta or alpha hemolysis
Hemolytic patterns help in classifying the Streptococcus species.
What distinguishes beta-hemolytic from alpha-hemolytic Streptococci?
Beta-hemolytic Streptococci completely lyse red blood cells, while alpha-hemolytic Streptococci partially lyse them.
This distinction is crucial for identification and treatment.
What is the resistance pattern for Group A Streptococci (Streptococcus pyogenes)?
Bacitracin-sensitive
This feature is used in laboratory identification of Group A streptococci.
What is the resistance pattern for Group B and C Streptococci?
Bacitracin-resistant
This characteristic helps differentiate them from Group A.
What is the sensitivity pattern for Streptococcus pneumoniae?
Optochin-sensitive
This sensitivity is used to identify Streptococcus pneumoniae in clinical samples.
What is the resistance pattern for viridans streptococci?
Optochin-resistant
This helps classify them separately from Streptococcus pneumoniae.
Fill in the blank: Streptococcus species are named after the type of _______ they possess on their cell walls.
[carbohydrate]
This naming convention is essential for the classification of Streptococci.
What is another name for Streptococcus Pyogenes?
Group A strep
Group A strep is commonly known for causing throat infections and skin diseases.
What shape and arrangement does Streptococcus pyogenes have?
Cocci/ovoid and in a row
The term ‘strep’ means rows, indicating their arrangement.
What is the Gram status of Streptococcus pyogenes?
Positive
This indicates the bacteria retain the crystal violet stain used in the Gram staining procedure.
What structural features does Streptococcus pyogenes possess?
Capsules and slime layers; no endospores or flagella
These features contribute to its virulence and ability to evade the immune system.
How does the colony morphology of Streptococcus pyogenes vary?
Varies based on capsule amount — can be large and gray to small and white
The appearance of colonies can indicate different strains or growth conditions.
What is the optimum temperature for the growth of Streptococcus pyogenes?
35 - 37°C
This range is typical for human pathogens as it aligns with human body temperature.
What type of oxygen requirement does Streptococcus pyogenes have?
Facultative anaerobe
This means it can grow in both the presence and absence of oxygen.
Is Streptococcus pyogenes tough against environmental factors?
Many are sensitive to drying, heat, and disinfectants
This sensitivity can affect its survival outside a host.
Where is Streptococcus pyogenes commonly located in humans?
Throat, nasopharynx, and skin
These locations are key for transmission and infection.
How is Streptococcus pyogenes transmitted?
Contact, droplets, fomites, food
Understanding transmission routes is crucial for prevention measures.
Do humans carry Streptococcus pyogenes?
Yes, humans are the ONLY carriers
Many individuals may be asymptomatic carriers, spreading the bacteria without showing symptoms.
Is Streptococcus pyogenes considered an opportunistic or true pathogen?
True pathogen
This indicates it can cause disease in healthy individuals, not just those with weakened immune systems.
What does the word Pyogenes mean in S. pyogenes?
Causes Puss
What is the function of C-carbohydrates in bacterial virulence?
Protects against lysozyme
C-carbohydrates are important for bacterial survival in hostile environments.
What role does lipoteichoic acid play?
Allows adhesion to epithelium
Lipoteichoic acid is found on fimbriae and is crucial for establishing infections.
What is the function of M protein in bacteria?
Adhesion and phagocytosis resistance
M protein helps bacteria evade the immune system and adhere to host tissues.
What is the composition of the capsule that mimics human skin?
Made of hyaluronic acid
This mimicry helps decrease the immune response from the host.
List the four virulence factors to remember.
- C-carbohydrates
- M-protein antigen
- Lipoteichoic acid
- Capsule made of hyaluronic acid
These factors contribute to the pathogenicity of certain bacteria.
Simple way to remember: Cell Layers Mask Camouflage
What is lysozyme?
An enzyme that breaks down bacterial cell walls
Lysozyme is part of the innate immune response and targets peptidoglycan.
What are streptolysins?
Beta hemolysins that also cause cell and tissue injury
Streptolysins are produced by certain strains of Streptococcus bacteria.
What is erythrogenic toxin?
A superantigen that induces fever and a typical red rash
Erythrogenic toxin is associated with scarlet fever.
What does streptokinase do?
Digests fibrin clots
Streptokinase is an enzyme that helps dissolve blood clots.
Fill in the blank: The enzyme _______ is used as a medication against blood clots in people.
streptokinase
Streptokinase is a therapeutic agent in treating thrombotic conditions.
What does hyaluronidase do?
Breaks down connective tissue
Hyaluronidase facilitates the spread of infection by degrading the extracellular matrix.
What is the function of peroxidase in comparison to catalase?
Converts hydrogen peroxide into molecules other than O2, but still releases water
This highlights the different substrate handling between peroxidase and catalase.
What are the major extracellular toxins of S. Pyogenes
- Streptolysins
- Erythrogenic toxin
These toxins play significant roles in the pathogenicity of certain bacteria.
What are the extracellular enzymes associated with S. Pyogenes
- Streptokinase
- Hyaluronidase
- Peroxidase
These enzymes contribute to the bacteria’s ability to invade tissues and evade the immune response.
What is impetigo?
Superficial lesions that break and form highly contagious crust.
True or False: Impetigo is not contagious.
False.
Fill in the blank: Erysipelas can be -
superficial or become systemic.
What factors contribute to the spread of impetigo?
- Insect bites * Poor hygiene * Crowded living conditions.
What is Erysipelas?
A skin infection where the pathogen enters through broken skin and spreads to the dermis (Middle skin layer) and subcutaneous (bottom layer of skin) tissues.
What clinical condition is associated with S. pyogenes?
Streptococcal pharyngitis (strep throat).
What are common symptoms of strep throat?
Symptoms include: * Red throat * Swollen tonsils * White patches on tonsils * Swollen lymph nodes * Petechiae.
What serious complications can arise from untreated strep throat?
Pneumonia, Sepsis, Toxic shock
Fill in the blank: Strep throat can damage the _____ of blood capillaries.
plasma membranes
True or False: Scarlet fever is a complication of strep throat.
True
