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Questions and Answers
Which mechanism is primarily responsible for the action of 70% ethanol as an antiseptic?
What is a primary purpose of performing clinical hand washing?
Which of the following factors primarily influences the types of normal flora found in the mouth compared to the skin?
Which antiseptic is known to act by disrupting cell walls and proteins?
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What type of items can be effectively sterilized using an autoclave?
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What is the effect of clinical hand washing on healthcare-associated infections (HAIs)?
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Which antiseptic is primarily used for pre-surgery skin treatment?
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In microbiology, what do the terms 'environmentally resistant' and 'environmentally sensitive' refer to?
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What is the primary function of superoxide dismutase (SOD) in oxygen-utilizing bacteria?
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Which type of bacteria is characterized by the inability to grow in the presence of oxygen?
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What differentiates facultative anaerobes from obligate aerobes?
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What role does catalase play in bacterial metabolism?
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Which oxygen requirement category of bacteria would display no growth in both 20.8% and 0% oxygen environments?
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Which enzyme is crucial for aerobic bacteria to detoxify superoxide radicals?
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What is the primary purpose of coagulase secretion by Staphylococcus aureus?
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What is a common feature of aerotolerant bacteria regarding oxygen usage?
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Which of the following correctly describes the condition of erysipelas?
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What is a characteristic feature of a furuncle?
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What distinguishes necrotizing fasciitis from other skin infections?
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Which bacterium is primarily responsible for causing abscesses?
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Which of the following statements about cellulitis is accurate?
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What is the correct definition of necrosis?
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Which condition is characterized by pus-filled lesions that typically measure less than 0.5 cm?
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What are leukocidins and their role in abscess formation?
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Study Notes
Autoclave Function
- Destroys all microorganisms, enzymes, and biomolecules
- Biologically sterilizes items
- Uses pressure to increase water's boiling point to 121°C for 20 minutes
Autoclave Uses
- Sterilizes microbial media
- Sterilizes surgical instruments
- Sterilizes biomedical waste
Aseptic Techniques
- Procedures ensuring no unwanted organisms enter pure cultures or the lab environment.
Aseptic Technique Items
- Sterile gloves
- Sterile gowns
- Masks for patient and healthcare provider
- Sterile drapes
Clinical Skin Treatment Purpose
- Removes all organisms from the skin, including staphylococci
- Decreases the risk and number of HAIs (Healthcare-Associated Infections)
- Reduces microbial load on healthcare workers and clinical surfaces.
Clinical Skin Treatment: 70% Ethanol
- Mechanism of action: Disrupts lipids and denatures proteins.
- Clinical applications: Venipuncture, IV line (small skin areas)
Clinical Skin Treatment: CHG (Chlorohexidine Gluconate)
- Mechanism of action: Disrupts cell walls and proteins.
- Clinical applications: Hibiclens clinical soap, clinical hand sanitizer, pre-surgical skin and hand treatment.
Clinical Skin Treatment: Betadine
- Mechanism of action: Iodine compound, an oxidizing agent that destroys biomolecules.
- Clinical application: Pre-surgical skin treatment left on skin 10-20 minutes prior to surgery.
Skin vs. Mouth Environments
- Compare and contrast: Skin and mouth environments differ in moisture levels, pH, tonicity, nutrient concentration, and competition.
- Environmentally resistant and sensitive species: The environment producing more resistant species is determined by the factors above.
Toxic Oxygen Molecules
- Origin: O2 enters the cell membrane and collides with H2O in the cytoplasm causing the production of toxic oxygen radicals (ROS).
- Mechanism of action: Toxic oxygen molecules act as oxidizing agents.
Specific Toxic Oxygen Molecules
- Superoxide anion (O2-): O2 + electron; very strong oxidizing agent.
- Hydrogen Peroxide (H2O2): H2O + O atom; strong oxidizing agent.
Detoxifying Enzymes
- Superoxide dismutase (SOD): converts O2- to H2O2 (hydrogen peroxide).
- Catalase: converts H2O2 into H2O & O2.
- Peroxidase: converts H202 into H2O.
Oxygen Requirement Classifications
- Obligate aerobe: Always uses oxygen.
- Enzymes: SOD, Catalase, Peroxidase
- Facultative anaerobe: Sometimes uses oxygen.
- Enzymes: SOD, Catalase
- Aerotolerant: Tolerant to oxygen, does not use it.
- Enzymes: SOD and Peroxidase
- Obligate anaerobe: Poisoned by oxygen, does not use it.
- No enzymes
Oxygen Classification Enzyme Distribution
- Obligate aerobe: SOD, Catalase, Peroxidase
- Facultative anaerobe: SOD and Catalase
- Aerotolerant: SOD and Peroxidase
- Obligate anaerobe: No Enzymes
Growth Patterns in Oxygen
- Obligate aerobe: Grows well in 20.8% oxygen, no growth in 0% oxygen.
- Facultative anaerobe: Grows well in 20.8% oxygen, grows fair in 0% oxygen (more growth with oxygen).
- Catalase: bubbles (+)
- Aerotolerant: Grows poor in 20.8% oxygen, grows poor in 0% oxygen (equivalent growth).
- Catalase: no bubbles (-)
- Obligate anaerobe: No growth in 20.8% oxygen, grows poor in 0% oxygen (dies in presence of oxygen).
Coagulase Species
- S.aureus
Coagulase Reaction
- Fibrinogen (soluble) → coagulase → Fibrin (insoluble)
- Coagulase converts fibrinogen into fibrin.
Coagulase Enzyme Purpose
- Evade the immune system (immunosubversion)
- Create a fibrin barrier during abscess formation.
Erysipelas
- Infection of the superficial layers of the skin.
- Characterized by swollen, bright red patches of skin with defined borders.
- Caused by Streptococcus pyogenes strains that secrete a specific protein toxin.
- Symptoms include pain, fever, chills, headache, and fatigue.
Abscess
- Conical swelling of tissue with redness and pain, often containing pus.
- Pus is a collection of destroyed white blood cells and cellular debris due to bacterial toxins.
- The epidermis remains intact.
- S.aureus is a common cause, but other species can also cause abscesses.
Pustule
- Abscess of the superficial dermis containing pus.
- Usually less than 0.5 cm.
- S.aureus is the most common cause.
Folliculitis
- Infection of hair follicles, consisting of vesicles and pustules.
- S.aureus is a common cause.
Furuncle
- Painful abscess nodule formed in dermal & subcutaneous tissues, containing pus (~1-3 cm).
- Typically caused by S.aureus.
Carbuncle
- Very large (3-12 cm), painful abscess with draining pus involving deep subcutaneous tissues.
- Extensive tissue destruction, fever, and sepsis complications are common.
- Typically caused by S.aureus.
Cellulitis
- Infection of dermal and subcutaneous tissues with undefined borders.
- Symptoms include redness, pain, and high fever (>104°F/40°C).
- Approximately 14 million cases/year in the U.S.
Necrosis
- Tissue death.
- Dead tissue needs to be removed from the body.
- Can have both infectious and non-infectious causes.
Necrotizing Fasciitis
- Rapidly spreading infection of dermal, subcutaneous, and fascia tissues.
- Symptoms include high fever and severe pain.
- Necrotic tissue must be surgically removed, and amputation may be required.
Oxygen Percentages
- Aerobic: 20.8%
- Anaerobic: 0.0%
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