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What is the typical arrangement of Streptococcus bacteria?
What is the typical arrangement of Streptococcus bacteria?
Which type of hemolysis is exhibited by Streptococcus pyogenes?
Which type of hemolysis is exhibited by Streptococcus pyogenes?
What classification method was developed by Rebecca Lancefield?
What classification method was developed by Rebecca Lancefield?
Which group does Streptococcus pyogenes belong to in the Lancefield classification?
Which group does Streptococcus pyogenes belong to in the Lancefield classification?
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What is the primary characteristic used to differentiate Streptococcus species at the species level?
What is the primary characteristic used to differentiate Streptococcus species at the species level?
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What is the diameter range of Streptococcus cocci?
What is the diameter range of Streptococcus cocci?
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What enzyme released by streptococci is responsible for hemolysis on blood agar?
What enzyme released by streptococci is responsible for hemolysis on blood agar?
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Which Lancefield group has the most clinical significance among beta-hemolytic streptococci?
Which Lancefield group has the most clinical significance among beta-hemolytic streptococci?
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What is a characteristic feature of Gram-positive bacteria?
What is a characteristic feature of Gram-positive bacteria?
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What type of hemolysis is associated with Streptococcus pyogenes?
What type of hemolysis is associated with Streptococcus pyogenes?
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Which of the following bacteria are included in the Streptococcus viridans group?
Which of the following bacteria are included in the Streptococcus viridans group?
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What differentiates Streptolysin O from Streptolysin S?
What differentiates Streptolysin O from Streptolysin S?
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What infections are commonly associated with Streptococcus mutans?
What infections are commonly associated with Streptococcus mutans?
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In which medical condition is the viridans group most notably involved?
In which medical condition is the viridans group most notably involved?
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Which of the following is NOT a characteristic of the viridans group of Streptococci?
Which of the following is NOT a characteristic of the viridans group of Streptococci?
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What is the primary function of Streptolysin produced by Streptococcus pyogenes?
What is the primary function of Streptolysin produced by Streptococcus pyogenes?
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What is the primary role of M protein in Group A Streptococcus?
What is the primary role of M protein in Group A Streptococcus?
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What is necrotizing fasciitis commonly referred to as?
What is necrotizing fasciitis commonly referred to as?
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How does the hyaluronic acid capsule contribute to the virulence of Group A Streptococcus?
How does the hyaluronic acid capsule contribute to the virulence of Group A Streptococcus?
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Which virulence factor is responsible for the destruction of red and white blood cells?
Which virulence factor is responsible for the destruction of red and white blood cells?
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What severe condition can result from the action of Streptococcal pyrogenic exotoxins (SPEs)?
What severe condition can result from the action of Streptococcal pyrogenic exotoxins (SPEs)?
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What is the common treatment for necrotizing fasciitis caused by Group A Streptococcus?
What is the common treatment for necrotizing fasciitis caused by Group A Streptococcus?
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What is the mechanism of action for streptokinase in Group A Streptococcus infections?
What is the mechanism of action for streptokinase in Group A Streptococcus infections?
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Which statement about Streptolysin O is true?
Which statement about Streptolysin O is true?
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What is the primary method through which Listeria monocytogenes causes illness in humans?
What is the primary method through which Listeria monocytogenes causes illness in humans?
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Which key component assists Listeria monocytogenes in moving within host cells?
Which key component assists Listeria monocytogenes in moving within host cells?
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What is the role of Listeriolysin produced by Listeria monocytogenes?
What is the role of Listeriolysin produced by Listeria monocytogenes?
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What is a common cause of necrotizing fasciitis?
What is a common cause of necrotizing fasciitis?
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Which groups of individuals are particularly at risk for Listeriosis?
Which groups of individuals are particularly at risk for Listeriosis?
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Which of the following statements about Sarcina ventriculi is true?
Which of the following statements about Sarcina ventriculi is true?
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What is the mortality rate associated with Listeria infections?
What is the mortality rate associated with Listeria infections?
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Which of the following genera includes the species Clostridium difficile and Clostridium botulinum?
Which of the following genera includes the species Clostridium difficile and Clostridium botulinum?
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Which of the following is a characteristic of Listeria monocytogenes?
Which of the following is a characteristic of Listeria monocytogenes?
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What type of bacteria is most commonly associated with causing foodborne illness?
What type of bacteria is most commonly associated with causing foodborne illness?
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What can Listeria monocytogenes lead to when infection occurs?
What can Listeria monocytogenes lead to when infection occurs?
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What contributes to the spread of Listeria infections?
What contributes to the spread of Listeria infections?
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At what temperature range can Listeria grow?
At what temperature range can Listeria grow?
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Study Notes
Gram Positive Bacteria: Streptococcus spp.
- Streptococcus bacteria are Gram-positive cocci, typically found in chains or pairs.
- Streptococcus species can be differentiated by their hemolytic activity on blood agar.
- Beta-hemolysis, which is complete red blood cell hemolysis, is diagnostic for Streptococcus pyogenes (Group A Streptococcus).
- Alpha-hemolysis (partial hemolysis) is characteristic of the viridans group streptococci.
- The viridans group includes Streptococcus anginosus, Streptococcus mitis, Streptococcus sanguinis, Streptococcus salivarius, Streptococcus mutans, Streptococcus gordonii, and Streptococcus oralis.
- Streptococcus mutans is associated with dental caries.
Streptolysin
- Streptolysins are toxins produced by certain Streptococcus bacteria, particularly Streptococcus pyogenes.
- Streptolysin O (SLO) is oxygen-sensitive and causes hemolysis under anaerobic conditions.
- Streptolysin S (SLS) is oxygen-stable and causes hemolysis under aerobic conditions.
- Both streptolysins contribute to the bacteria's ability to lyse red blood cells and evade the immune system.
Lancefield Grouping
- Streptococci are classified into serological groups (A-H, K-V) based on the presence of group-specific wall polysaccharides known as Lancefield antigens.
- Streptococcus pyogenes is the only bacterium within the Lancefield Group A classification.
Virulence Factors of Streptococcus pyogenes
- M Protein: A surface protein that inhibits phagocytosis by preventing complement deposition and opsonization.
- Hyaluronic Acid Capsule: Mimics human hyaluronic acid, allowing evasion of the immune system by hiding from phagocytes.
- Streptolysins (S and O): Hemolysins that lyse cells, including red blood cells, white blood cells, and platelets, contributing to tissue damage and inflammation.
- Streptococcal Pyrogenic Exotoxins (SPEs): Superantigens that can cause streptococcal toxic shock syndrome (STSS) and scarlet fever.
- Streptokinase: Converts plasminogen to plasmin, which breaks down fibrin clots.
Necrotizing Fasciitis
- Necrotizing fasciitis, commonly known as “flesh eating disease", is a serious condition caused by Streptococcus pyogenes.
- It can also be caused by a combination of bacteria including Staphylococcus aureus and Clostridium perfringens.
Firmicutes: Nonsporulating Bacillales and Clostridiales
- Key genera: Listeria, Sarcina, Clostridium
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Listeria:
- Found widely in soils, an opportunistic pathogen that causes foodborne illness.
- Gram-positive, catalase-positive, rod-shaped, facultatively aerobic chemoorganotrophs.
- Acid-, salt-, and cold-tolerant.
- Listeria monocytogenes causes listeriosis, a serious infection that can be fatal, especially in pregnant women, newborns, and individuals with weakened immune systems.
-
Sarcina:
- Catalase-negative.
- Obligate anaerobe, exceptionally acid tolerant, often found in the stomach.
- Sarcina ventriculi is associated with pyloric ulceration.
-
Clostridium:
- Includes important pathogens like Clostridium difficile, Clostridium botulinum, Clostridium tetani, and Clostridium perfringens.
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Description
This quiz focuses on the characteristics and differentiation of Streptococcus bacteria, highlighting their hemolytic activity and specific species. Learn about beta-hemolysis, alpha-hemolysis, and the role of streptolysins in pathogenicity.
