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Questions and Answers
Which of the following describes the function of keratin in the skin?
Which of the following describes the function of keratin in the skin?
Which of the following bacterial species is not typically found in normal skin microbial flora?
Which of the following bacterial species is not typically found in normal skin microbial flora?
What distinguishes β-hemolytic streptococci from other types?
What distinguishes β-hemolytic streptococci from other types?
Which characteristic is true about Streptococcus pyogenes?
Which characteristic is true about Streptococcus pyogenes?
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What is the primary defense function of sebum?
What is the primary defense function of sebum?
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Which of the following statements is true regarding the metabolic activity of streptococci?
Which of the following statements is true regarding the metabolic activity of streptococci?
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Which of the following best defines medical microbiology?
Which of the following best defines medical microbiology?
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What type of infection arises from microorganisms originating from external sources?
What type of infection arises from microorganisms originating from external sources?
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Which type of pathogen is always associated with human disease?
Which type of pathogen is always associated with human disease?
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In what settings are nosocomial infections typically acquired?
In what settings are nosocomial infections typically acquired?
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Why are opportunistic pathogens particularly concerning for patients with defective immune systems?
Why are opportunistic pathogens particularly concerning for patients with defective immune systems?
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What is a blood agar plate primarily used for?
What is a blood agar plate primarily used for?
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Which component in blood agar plates helps in enriching the medium?
Which component in blood agar plates helps in enriching the medium?
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What pH range is desired for the nutrient agar in blood agar plates?
What pH range is desired for the nutrient agar in blood agar plates?
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At what temperature should the mixture be autoclaved for preparing blood agar plates?
At what temperature should the mixture be autoclaved for preparing blood agar plates?
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What is the primary purpose of Chocolate agar?
What is the primary purpose of Chocolate agar?
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Which type of hemolysis indicates complete lysis and digestion of red blood cells?
Which type of hemolysis indicates complete lysis and digestion of red blood cells?
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Which of the following correctly describes γ-hemolysis?
Which of the following correctly describes γ-hemolysis?
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What common mechanism can compromise the skin barrier leading to SSTIs?
What common mechanism can compromise the skin barrier leading to SSTIs?
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What structure is found in the dermis layer of the skin?
What structure is found in the dermis layer of the skin?
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In the context of SSTIs, what does the term 'soft tissue' refer to?
In the context of SSTIs, what does the term 'soft tissue' refer to?
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What is a common clinical challenge related to SSTIs?
What is a common clinical challenge related to SSTIs?
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What is a characteristic of the epidermis layer of skin?
What is a characteristic of the epidermis layer of skin?
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What condition can commonly lead to a break in the skin barrier, resulting in potential SSTIs?
What condition can commonly lead to a break in the skin barrier, resulting in potential SSTIs?
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Which component is NOT typically found in the hypodermis layer of skin?
Which component is NOT typically found in the hypodermis layer of skin?
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What is the primary characteristic of necrotizing fasciitis?
What is the primary characteristic of necrotizing fasciitis?
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Which virulence factor is primarily associated with the ability of S. pyogenes to invade host cells?
Which virulence factor is primarily associated with the ability of S. pyogenes to invade host cells?
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Which condition is characterized by localized pain, inflammation, and systemic symptoms related to skin infection?
Which condition is characterized by localized pain, inflammation, and systemic symptoms related to skin infection?
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Which of the following factors contributes to the virulence of Streptococcus pyogenes by enabling it to evade the immune response?
Which of the following factors contributes to the virulence of Streptococcus pyogenes by enabling it to evade the immune response?
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What common characteristic is shared among most species of Staphylococcus?
What common characteristic is shared among most species of Staphylococcus?
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In compound skin infections, what is a defining feature of cellulitis?
In compound skin infections, what is a defining feature of cellulitis?
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What is a key clinical presentation of Streptococcal toxic shock syndrome?
What is a key clinical presentation of Streptococcal toxic shock syndrome?
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What is primarily responsible for the yellow or gold color of aureus colonies?
What is primarily responsible for the yellow or gold color of aureus colonies?
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Which of the following diseases is associated with scalded skin syndrome?
Which of the following diseases is associated with scalded skin syndrome?
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What is a recognized virulence factor of Staphylococcus aureus that aids in evading the immune response?
What is a recognized virulence factor of Staphylococcus aureus that aids in evading the immune response?
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What type of toxin is responsible for the massive release of cytokines causing hypotension and shock in toxic shock syndrome?
What type of toxin is responsible for the massive release of cytokines causing hypotension and shock in toxic shock syndrome?
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Which of the following is NOT a systemic disease associated with Staphylococcus aureus?
Which of the following is NOT a systemic disease associated with Staphylococcus aureus?
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What characteristic of Staphylococcus aureus allows it to survive for extended periods on dry surfaces?
What characteristic of Staphylococcus aureus allows it to survive for extended periods on dry surfaces?
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Which method is used by the exfoliative toxin of aureus to interact with the immune system?
Which method is used by the exfoliative toxin of aureus to interact with the immune system?
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What does the term 'facultative anaerobe' imply about Staphylococcus aureus?
What does the term 'facultative anaerobe' imply about Staphylococcus aureus?
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Which population is particularly affected by scalded skin syndrome?
Which population is particularly affected by scalded skin syndrome?
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What is the main reason Pseudomonas aeruginosa is resistant to many antibiotics?
What is the main reason Pseudomonas aeruginosa is resistant to many antibiotics?
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Which of the following environments is NOT typically associated with the presence of Pseudomonas aeruginosa?
Which of the following environments is NOT typically associated with the presence of Pseudomonas aeruginosa?
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What characterizes the growth of Pseudomonas aeruginosa colonies on a blood agar plate?
What characterizes the growth of Pseudomonas aeruginosa colonies on a blood agar plate?
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What is a significant risk factor for infections caused by Methicillin-resistant Staphylococcus aureus (MRSA)?
What is a significant risk factor for infections caused by Methicillin-resistant Staphylococcus aureus (MRSA)?
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What is a common disease linked to infections from Pseudomonas aeruginosa?
What is a common disease linked to infections from Pseudomonas aeruginosa?
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Which of the following statements best describes the nutritional needs of Pseudomonas aeruginosa?
Which of the following statements best describes the nutritional needs of Pseudomonas aeruginosa?
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What type of infectious transmission is primarily associated with the spread of MRSA?
What type of infectious transmission is primarily associated with the spread of MRSA?
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What characteristic of Pseudomonas aeruginosa contributes to its classification as an opportunistic pathogen?
What characteristic of Pseudomonas aeruginosa contributes to its classification as an opportunistic pathogen?
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Which of the following is NOT a typical characteristic of Pseudomonas aeruginosa?
Which of the following is NOT a typical characteristic of Pseudomonas aeruginosa?
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What range of diameters do aerosols produced by sneezing and coughing typically fall under?
What range of diameters do aerosols produced by sneezing and coughing typically fall under?
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Which of the following diseases is caused by a bacterial pathogen that can be transmitted through aerosols?
Which of the following diseases is caused by a bacterial pathogen that can be transmitted through aerosols?
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What is the primary method to decrease airborne disease transmission?
What is the primary method to decrease airborne disease transmission?
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Which condition is NOT transmitted through aerosols?
Which condition is NOT transmitted through aerosols?
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What type of colloid describes aerosols?
What type of colloid describes aerosols?
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Which of the following examples best illustrates an aerosol?
Which of the following examples best illustrates an aerosol?
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Which part of the respiratory tract is primarily responsible for the passage of air to the lungs?
Which part of the respiratory tract is primarily responsible for the passage of air to the lungs?
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What factor significantly differentiates the infectious characteristics of the lepromatous and tuberculoid forms of disease?
What factor significantly differentiates the infectious characteristics of the lepromatous and tuberculoid forms of disease?
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Which of the following organisms is least likely to be pathogenic when found in the upper respiratory tract?
Which of the following organisms is least likely to be pathogenic when found in the upper respiratory tract?
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What is the main function of the mucociliary clearance mechanism in the respiratory tract?
What is the main function of the mucociliary clearance mechanism in the respiratory tract?
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How do goblet cells contribute to the defense mechanisms of the respiratory tract?
How do goblet cells contribute to the defense mechanisms of the respiratory tract?
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What characteristic is true about the lower respiratory tract in terms of microorganism presence?
What characteristic is true about the lower respiratory tract in terms of microorganism presence?
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Which type of microorganism is predominantly found in the upper respiratory tract, according to quantity?
Which type of microorganism is predominantly found in the upper respiratory tract, according to quantity?
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What does the ciliary action in the mucociliary blanket accomplish?
What does the ciliary action in the mucociliary blanket accomplish?
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Which anatomical component follows the bronchi in the pathway of inhaled air?
Which anatomical component follows the bronchi in the pathway of inhaled air?
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What is the size threshold for infectious particles to be efficiently trapped by the mucociliary blanket?
What is the size threshold for infectious particles to be efficiently trapped by the mucociliary blanket?
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What is a primary characteristic of the lepromatous form of leprosy?
What is a primary characteristic of the lepromatous form of leprosy?
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Which of the following best describes Mycobacterium leprae?
Which of the following best describes Mycobacterium leprae?
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What is a commonality between the reported cases of leprosy in 2005?
What is a commonality between the reported cases of leprosy in 2005?
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How is leprosy primarily transmitted?
How is leprosy primarily transmitted?
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Which cellular immune response is observed in patients with tuberculoid leprosy?
Which cellular immune response is observed in patients with tuberculoid leprosy?
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What is a defining feature of Mycobacterium leprae that affects its culturing?
What is a defining feature of Mycobacterium leprae that affects its culturing?
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In the pathogenesis of leprosy, what characteristic distinguishes lepromatous leprosy from tuberculoid leprosy?
In the pathogenesis of leprosy, what characteristic distinguishes lepromatous leprosy from tuberculoid leprosy?
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Why might leprosy have a low reported incidence despite its historical prevalence?
Why might leprosy have a low reported incidence despite its historical prevalence?
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What type of staining is used to visualize Mycobacterium leprae due to its cell wall composition?
What type of staining is used to visualize Mycobacterium leprae due to its cell wall composition?
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Which of the following diseases is primarily characterized by inflammation of the tonsils?
Which of the following diseases is primarily characterized by inflammation of the tonsils?
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Which pathogen is known as the causative agent of whooping cough?
Which pathogen is known as the causative agent of whooping cough?
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What is a common feature of middle ear infections?
What is a common feature of middle ear infections?
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Which of the following infections primarily affects infants and young children under two years of age?
Which of the following infections primarily affects infants and young children under two years of age?
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Which bacterium is commonly associated with ear infections?
Which bacterium is commonly associated with ear infections?
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What type of respiratory tract infection is characterized by inflammation of the larynx?
What type of respiratory tract infection is characterized by inflammation of the larynx?
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Which pathogen is most likely to cause persistent bacterial infection in the lungs?
Which pathogen is most likely to cause persistent bacterial infection in the lungs?
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Inflammation associated with the 'itis' suffix primarily indicates what in a disease context?
Inflammation associated with the 'itis' suffix primarily indicates what in a disease context?
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What was a significant outcome of the Legionnaires' disease outbreak in 1976?
What was a significant outcome of the Legionnaires' disease outbreak in 1976?
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Which of the following pathogens does NOT commonly cause respiratory tract infections?
Which of the following pathogens does NOT commonly cause respiratory tract infections?
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Which of the following accurately describes the bacterium Legionella and its mechanism?
Which of the following accurately describes the bacterium Legionella and its mechanism?
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Why might Legionnaires' disease be mistaken for other illnesses?
Why might Legionnaires' disease be mistaken for other illnesses?
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What is the primary mode of transmission for Legionnaires' disease?
What is the primary mode of transmission for Legionnaires' disease?
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What is a critical implication of failing to correctly diagnose Legionnaires' disease?
What is a critical implication of failing to correctly diagnose Legionnaires' disease?
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Which types of environments are most likely to harbor Legionella bacteria?
Which types of environments are most likely to harbor Legionella bacteria?
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What is the primary feature of the paroxysmal stage of whooping cough?
What is the primary feature of the paroxysmal stage of whooping cough?
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Which treatment is most effective in decreasing the infectious stage of pertussis?
Which treatment is most effective in decreasing the infectious stage of pertussis?
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Why are Legionella considered nutritionally fastidious organisms?
Why are Legionella considered nutritionally fastidious organisms?
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What distinguishes the causative agent of Pontiac fever from other Legionella diseases?
What distinguishes the causative agent of Pontiac fever from other Legionella diseases?
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Which of the following characterizes the lifecycle of Legionella bacteria?
Which of the following characterizes the lifecycle of Legionella bacteria?
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What component in vaccines is crucial for eliciting an effective immune response against pertussis?
What component in vaccines is crucial for eliciting an effective immune response against pertussis?
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Which statement is true regarding the range of Legionella species?
Which statement is true regarding the range of Legionella species?
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In which stage does whooping cough display catarrhal symptoms resembling the common cold?
In which stage does whooping cough display catarrhal symptoms resembling the common cold?
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Which is a lesser-known complication linked to pertussis in adults?
Which is a lesser-known complication linked to pertussis in adults?
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Which clinical feature is indicative of the convalescence stage of whooping cough?
Which clinical feature is indicative of the convalescence stage of whooping cough?
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Study Notes
Medical Microbiology
- Medical microbiology is the study of interactions between animals (primarily humans) and microorganisms (bacteria, viruses, fungi, and parasites), focusing on diseases caused by these interactions.
Infection Concepts
- Exposure to an organism can lead to transient colonization, permanent colonization, or disease.
- Exogenous infections arise from external sources.
- Endogenous infections originate from the person's own microbes spreading to inappropriate sites.
- Nosocomial infections are acquired in hospitals.
Pathogen Types
- Strict pathogens are always associated with human disease (e.g., Mycobacterium tuberculosis).
- Opportunistic pathogens are normally part of the body's microbial flora but cause disease in compromised individuals (e.g., Staphylococcus aureus, Escherichia coli, Candida albicans).
Bacterial Classification
- Fastidious organisms require rich media, often containing blood components, to grow.
Blood Agar Plate (BAP)
- Enriched with mammalian blood (usually sheep or horse), typically at 5-10% concentration.
- Components: 0.5% Peptone, 0.3% beef extract/yeast extract, 1.5% agar, 0.5% NaCl, distilled water.
- pH should be from 7.2 to 7.6 (7.4).
- Autoclave the mixture at 121°C for 15 minutes, let it cool to 45-50°C, and add 5% defibrinated blood.
- Mix gently.
Chocolate Agar (CHOC)
- Type of blood agar where red blood cells are lysed by heating to 80°C.
- Used to grow fastidious respiratory bacteria like Haemophilus influenzae.
Hemolysis
- Hemolysis is the lysis of red blood cells.
- Alpha (α)-hemolysis: incomplete hemolysis.
- Beta (β)-hemolysis: complete lysis and digestion of red blood cell contents.
- Gamma (γ)-hemolysis: no hemolysis.
Skin and Soft Tissue Infections (SSTIs)
- Various presentations, etiologies, and severities involving microbial invasion of skin and underlying tissues.
- Soft tissue includes: muscles, tendons, ligaments, fascia, nerves, fibrous tissues, fat, blood vessels, and synovial membranes.
- Common entry points are breaks in the skin barrier: lacerations, bite wounds, scratches, instrumentation, pre-existing conditions (e.g., chicken pox, ulcers), burns, and surgery.
- Diagnosing SSTIs requires differentiating life-threatening cases from less severe ones.
Skin structure
- Epidermis: outermost layer, containing keratinocytes (95%) and melanocytes.
- Dermis: contains connective tissue, fibers, glycoproteins, nerve endings, hair follicles, glands, and blood vessels.
- Hypodermis (subcutaneous tissue): attaches skin to bone and muscle, containing fibroblasts, macrophages, and adipocytes (fat).
Natural Skin Defenses
- Keratin: a protein forming the basis of horny epidermal tissues (hair, nails).
- Skin cell shedding and regeneration.
- Sebum: oily, waxy substance; low pH, high lipid content.
- Sweat: low pH, high salt, and contains lysozyme (digests peptidoglycan).
- Normal skin microbiome.
Skin Normal Microbiota
- Propionibacterium acnes
- Staphylococci (e.g., Staphylococcus epidermidis, Staphylococcus aureus - in smaller numbers)
- Streptococci species
- Corynebacterium species
- Peptostreptococcus species
- Acinetobacter species
- Small numbers of other species (e.g., Pseudomonas aeruginosa, Candida species).
Streptococcus
- Gram-positive cocci arranged in pairs or chains.
- Most species are facultative anaerobes with complex nutritional requirements, needing blood or serum-enriched media for isolation.
- Carbohydrate fermentation results in lactic acid production.
- Catalase-negative streptococci.
- Divided into groups (β-hemolytic, α-hemolytic, and γ-hemolytic) based on hemolysis patterns, classified by Lancefield grouping or biochemical testing.
Streptococcus pyogenes
- Streptococcus pyogenes is a rapidly growing gram-positive coccus arranged in chains.
- Streptococcus pyogenes causes a variety of diseases, including pharyngitis, skin and soft-tissue infections, bacteremia, rheumatic fever, and acute glomerulonephritis.
- Streptococcus pyogenes is commonly called "flesh-eating" bacteria due to its necrotic damage to muscle tissue.
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Description
Explore the essential concepts of medical microbiology, focusing on the interactions between humans and microorganisms. Learn about infection types, pathogen classifications, and the significance of various microbial organisms in health and disease.