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Questions and Answers
What is the main effect of Toxic Shock Syndrome Toxin produced by certain strains of Staphylococcus aureus?
Which characteristic is true for the enterotoxins produced by Staphylococcus aureus?
How is Panton-Valentine leukocidin primarily encoded?
What type of genetic element carries the genes for staphylococcal enterotoxins?
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Which of the following statements correctly describes the nature of staphylococcal enterotoxins?
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What is the primary role of Protein A in bacterial virulence?
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Which of the following substances is associated with the anti-phagocytic properties in the cell wall components?
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What is a significant characteristic of exfoliative toxins?
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Coagulase's primary function is to:
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Toxic Shock Syndrome Toxin is primarily associated with which of the following?
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Enterotoxins primarily cause which of the following effects?
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Which cell wall component is specifically involved in adherence to mucosal surfaces?
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Which pair of components best explains the pathogenic potential of staphylococci?
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What is the primary role of coagulase in Staphylococcus aureus infections?
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How does Toxic Shock Syndrome Toxin (TSST) contribute to disease pathology?
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Which food type is most commonly associated with Staphylococcal food poisoning?
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What action does Protein A perform to enhance the virulence of Staphylococcus aureus?
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Which feature is characteristic of invasive conditions caused by Staphylococcus aureus?
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Which of the following diseases is categorized under toxigenic staphylococcal diseases?
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What is the main characteristic of abscess formation caused by Staphylococcus aureus?
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What type of toxin is primarily responsible for food poisoning in staphylococcal infections?
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Study Notes
Pathogenesis and Virulence Factors
- Staphylococcal toxins are encoded on chromosomal elements called pathogenicity islands.
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Toxic shock syndrome toxin is produced by strains that cause toxic shock syndrome.
- This toxin is a superantigen.
- It causes fever, a rash, shock, and multisystem involvement.
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Enterotoxins are produced by 50% of Staphylococcus aureus strains.
- These toxins are heat-stable and resistant to gut enzymes.
- They cause diarrhea and vomiting associated with staphylococcal food poisoning.
- The toxins are also superantigens.
- There are multiple types of enterotoxins (A-E, G-J, K-R, and U,V).
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Panton-Valentine Leukocidin is produced mainly by community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA).
- It is encoded on a mobile phage.
- It lyses leukocytes, releasing inflammatory mediators that lead to necrosis and severe inflammation.
Cell Wall Components
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Protein A binds to the Fc portion of IgG at the complement binding site, preventing complement activation.
- This reduces opsonization and phagocytosis of the organism.
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Teichoic Acid mediates adherence to mucosal surfaces.
- It also has endotoxin-like properties.
- Peptidoglycan forms a microcapsule that is anti-phagocytic.
- Polysaccharide is also anti-phagocytic.
Enzymes and Toxins
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Coagulase is a surface protein that causes coagulation of plasma.
- This results in fibrin deposition around lesions.
- This rendering the organism more resistant to phagocytosis.
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Clumping Factor is an adhesin that allows for adherence to fibrinogen and fibrin in plasma.
- It promotes aggregation of the organism and promotes attachment to blood clots and traumatized tissues.
- It increases the invasive pathogenic potential of the bacteria.
- Catalase limits the ability of phagocytic cells to kill bacteria by degrading hydrogen peroxide (H2O2).
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Exfoliative Toxins consist of two distinct proteins (A and B).
- They are epidermolytic and cause desquamation seen in the staphylococcal "scalded skin syndrome" in young children.
- These toxins are superantigens.
- Hemolysins and other enzymes are produced by Staphylococcus aureus.
Diseases Caused by Staphylococcus aureus
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Pyogenic (Pus-Forming) Staphylococcal Diseases
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Focal Suppuration
- Abscess formation is common in Staphylococcal infections.
- The presence of coagulase contributes to abscess formation by depositing fibrin around the lesions.
- Examples include folliculitis, carbuncles, boils, and abscesses.
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Invasive Conditions
- Organisms can spread via lymphatics or blood (bacteremia) to other parts of the body.
- This can cause deep-seated lesions such as osteomyelitis, necrotizing pneumonia, empyema, endocarditis, meningitis, multiple abscesses in tissues, and septicemia.
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Outbreaks
- Hospital-acquired post-operative wound infections are common, particularly with antibiotic-resistant strains.
- Foreign bodies, such as sutures and intravenous catheters, predispose to these infections.
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Focal Suppuration
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Toxigenic Staphylococcal Diseases
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Food Poisoning
- This is caused by ingestion of preformed enterotoxin in contaminated food that is improperly cooked and kept unrefrigerated.
- The source of contamination is often the hands or nose of a cook or food handler.
- Carbohydrate-rich foods such as cakes, pastry, and milk products are often the source of food poisoning.
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Food Poisoning
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