Questions and Answers
What are the general characteristics of Staphylococcus?
Staphylococcus is a motile organism.
False
What is Protein A known for in Staphylococcus?
Antiphagocytic
Which of the following is a virulence factor of Staphylococcus?
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What skin lesion is characterized by a change in color and is flat?
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What is a characteristic of a pustule?
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Staphylococcus aureus can cause __________, characterized by small, superficial abscesses.
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What syndrome is caused by exfoliative toxin in Staphylococcus?
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Which Staphylococcus species is associated with urinary tract infections?
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Toxic shock syndrome is common in menstruating women due to tampon use.
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What is the short incubation period for Staphylococcal gastroenteritis?
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Study Notes
General Characteristics
- Staphylococcus is a Gram-positive bacterium with spherical cells arranged in grape-like clusters.
- Commonly found on skin and mucous membranes; it is non-motile and non-spore forming.
- Facultative anaerobes, capable of aerobic and anaerobic respiration, and active fermenters.
- Colonies produce pigments resulting in white to deep yellow appearances.
- Known for easily acquiring antibiotic resistance and producing catalase, differentiating it from Streptococci, which are catalase negative.
Virulence Factors
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Cell Wall Components:
- Protein A: Anti-phagocytic, helps evade immune response.
- Fibronectin-binding protein (PnBP): Promotes adhesion to tissues.
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Exotoxins:
- Cytolytic exotoxins like hemolysin can lyse red blood cells.
- Superantigen exotoxins heighten T lymphocyte activity, including enterotoxins and toxic shock syndrome toxin.
- Exfoliative toxin leads to scalded skin syndrome.
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Enzymatic Factors:
- Coagulase: Clots plasma, aiding in localizing infection.
- Catalase: Converts hydrogen peroxide to water and oxygen.
- Other enzymes include hyaluronidase, staphylokinase, lipases, and nucleases which facilitate spreading.
Types of Skin Lesions
- Macules: Flat, discolored lesions.
- Papules: Raised lesions, solid, <5 mm in diameter.
- Plaques: Elevated flat lesions, >5 mm in diameter.
- Nodules: Rounded raised lesions, >5 mm in diameter.
- Urticaria: Pinkish annular papules or plaques, also known as hives.
- Vesicles: Fluid-filled lesions, <5 mm in diameter.
- Bullae: Larger fluid-filled lesions, >5 mm in diameter.
- Pustules: Lesions filled with exudate.
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Purpura: Skin bleeds resulting in:
- Petechiae: <3 mm.
- Ecchymosis: >3 mm.
- Ulcer: Crater-like lesions affecting deeper skin layers.
- Eschar: Necrotic ulcer covered with blackened scab.
Staphylococcus aureus Pathology
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Localized Skin Infections:
- STY: Small abscesses around hair follicles or glands.
- FURUNCLES/BOILS: Subcutaneous abscesses, often secondary to foreign bodies.
- CARBUNCLE: Deep, multiloculated infections that can spread systemically.
- IMPETIGO: Superficial, spreading crusted lesions.
- Staphylococcal scalded skin syndrome (Ritter’s disease): Common in infants; characterized by perioral erythema, Nikolsky sign, blistering, and desquamation.
Complications of Staphylococcus aureus
- Localized infections may lead to:
- Osteomyelitis (bone infection).
- Arthritis.
- Acute endocarditis (infection of heart valves).
- Septicemia (blood infection).
- Pneumonia and potential empyema (lung abscess).
Toxic Shock Syndrome
- Associated with tampons in menstruating women (first identified in the 1970s).
- Symptoms include fever, vomiting, diarrhea, hypotension, rash, and multi-organ involvement.
Staphylococcal Gastroenteritis
- Symptoms involve nausea, vomiting, and diarrhea without fever, with a quick onset (30 minutes to 8 hours post-exposure).
Coagulase Negative Staphylococcus
- Staphylococcus epidermidis: Infects prosthetic devices.
- Staphylococcus saprophyticus: Common cause of urinary tract infections.
Epidemiology
- Staphylococcus species are ubiquitous in the environment.
- Transmission occurs through droplets and drainage from lesions.
- Hygiene, cleanliness, and aseptic management are vital for control, alongside methods like aerosols, ultraviolet irradiation, and antiseptics.
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Description
This quiz explores the general characteristics and virulence factors of Staphylococcus, focusing on its structure, growth conditions, and antibiotic resistance. It highlights unique features like Protein A and the significance of catalase production. Test your knowledge about this important bacterial genus.
