Skin Structure, Function & Microbiota

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Questions and Answers

Sebum and perspiration provide nutrients to the skin. Which of these factors found in these secretions inhibits microbial growth?

  • Lysozyme (correct)
  • Amino acids
  • Fatty acids
  • Peptidoglycan

Which characteristic of mucous membranes provides protection against pathogens?

  • Washing by tears containing lysozyme (correct)
  • Production of sebum
  • Secretion of keratin
  • High pH

A patient has a Gram-positive, salt-tolerant bacterial infection on their skin. What genera would be MOST likely to cause this infection?

  • Pseudomonas
  • Escherichia
  • Staphylococcus (correct)
  • Clostridium

Which condition is characterized by a skin rash arising from a separate infection site?

<p>Exanthem (A)</p> Signup and view all the answers

A microbiologist is examining a skin lesion containing fluid and is approximately 1 cm in diameter. What type of lesion is this MOST likely to be?

<p>Vesicle (B)</p> Signup and view all the answers

How would you differentiate Staphylococcus from Streptococcus in a laboratory setting?

<p>By testing for coagulase production (D)</p> Signup and view all the answers

Staphylococcus aureus resists opsonization, meaning it can:

<p>Resist engulfment by phagocytes. (A)</p> Signup and view all the answers

A patient presents with inflammation of the tissue under the skin. What condition does this describe?

<p>Carbuncle (D)</p> Signup and view all the answers

Which virulence factor is associated with Streptococcus pyogenes?

<p>M protein (C)</p> Signup and view all the answers

Why does necrotizing fasciitis caused by Streptococcus pyogenes progress so rapidly?

<p>It releases Exotoxin A, acting as a superantigen. (C)</p> Signup and view all the answers

What feature is associated with Pseudomonas aeruginosa infections?

<p>Blue-green pus (C)</p> Signup and view all the answers

Which causative agent results in deep, damaging ulcers and exceeds the incidence of leprosy?

<p><em>Mycobacterium ulcerans</em> (A)</p> Signup and view all the answers

A patient has mild acne characterized by blocked sebum channels and shed cells. Which classification of acne is this?

<p>Comedonal (D)</p> Signup and view all the answers

Which treatment targets mild acne (comedonal) by removing dead skin cells?

<p>Salicylic acid (D)</p> Signup and view all the answers

Which of the following is transmitted via the respiratory route and causes pus-filled vesicles?

<p>Chickenpox (C)</p> Signup and view all the answers

A key feature of shingles is the reactivation of latent HHV-3 that moves along peripheral nerves. What vaccine can prevent shingles?

<p>Live attenuated vaccine (D)</p> Signup and view all the answers

What viral disease is characterized by a macular rash and Koplik's spots?

<p>Measles (B)</p> Signup and view all the answers

Which viral infection is associated with congenital defects when contracted during pregnancy?

<p>Rubella (C)</p> Signup and view all the answers

Fifth disease is caused by human parvovirus B19, which produces mild flu-like symptoms and what distinguishable feature?

<p>Facial rash (D)</p> Signup and view all the answers

Which fungal genera is commonly associated with infections of the hair, skin, and nails?

<p><em>Trichophyton</em> (B)</p> Signup and view all the answers

How does sporotrichosis typically enter the body?

<p>Through a puncture wound (A)</p> Signup and view all the answers

Candida albicans can cause thrush, which is characterized by:

<p>Infection of mucous membranes of the mouth. (D)</p> Signup and view all the answers

What is the primary treatment for candidiasis?

<p>Topical or systemic antifungals (B)</p> Signup and view all the answers

Sarcoptes scabiei causes scabies by:

<p>Burrowing in the skin to lay eggs. (A)</p> Signup and view all the answers

Pediculus humanus capitis is the causative agent for:

<p>Head lice (C)</p> Signup and view all the answers

What is the MOST effective preventative measure against ophthalmia neonatorum?

<p>Treating a newborn's eyes with antibiotics (A)</p> Signup and view all the answers

Which of the following eye diseases can be spread through swimming pool water?

<p>Inclusion conjunctivitis (B)</p> Signup and view all the answers

Untreated trachoma can lead to blindness as a result of:

<p>Corneal abrasion due to scarring (C)</p> Signup and view all the answers

What is the causative agent for herpetic keratitis?

<p>Herpes simplex virus 1 (HSV-1) (B)</p> Signup and view all the answers

A patient who wears contact lenses has Acanthamoeba keratitis. What is the MOST likely source of the infection?

<p>Unsanitary contact lenses (B)</p> Signup and view all the answers

Why is lysozyme an effective defense against microbes?

<p>It hydrolyzes peptidoglycan. (A)</p> Signup and view all the answers

Why are skin infections more likely to be caused by gram-positive bacteria?

<p>Gram-positive bacteria are more resistant to salt. (B)</p> Signup and view all the answers

Which of the following is NOT a typical characteristic of Staphylococcus aureus?

<p>Coagulase-negative (D)</p> Signup and view all the answers

Which of the lesions is described as an abscess with pus surrounded by inflamed tissue?

<p>Furuncle (C)</p> Signup and view all the answers

Which bacterial species produces hemolysins, hyaluronidase, and M proteins, contributing to its virulence?

<p>Streptococcus pyogenes (A)</p> Signup and view all the answers

Otitis externa, commonly known as 'swimmer's ear,' is often caused by:

<p>Pseudomonas aeruginosa. (D)</p> Signup and view all the answers

Which virus remains latent in dorsal root ganglia and can reactivate to cause shingles?

<p>Varicella-zoster virus (C)</p> Signup and view all the answers

Which of the following is a common treatment for warts caused by papillomaviruses?

<p>Cryotherapy (C)</p> Signup and view all the answers

A systemic fungal infection, often resulting from antibiotic use suppressing competing bacteria, is MOST likely:

<p>Candidiasis (D)</p> Signup and view all the answers

Flashcards

Conjunctivitis

An inflammation of the conjunctiva.

Exanthem

Skin rash arising from another focus of the infection

Enanthem

Mucous membrane rash arising from another focus of the infection

Folliculitis

Infections of the hair follicles.

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Sty

Folliculitis of an eyelash

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Furuncle

Abscess; pus surrounded by inflamed tissue.

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Carbuncle

Inflammation of tissue under the skin.

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Impetigo

Crusting (nonbullous) sores, spread by autoinoculation.

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Staphylococcus epidermidis

Gram-positive cocci, coagulase-negative.

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Staphylococcus aureus

Gram-positive cocci, coagulase-positive

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Streptococcus pyogenes

Infections caused by Group A beta-hemolytic streptococci; presenting with necrotizing fasciitis or erysipelas.

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Pseudomonas aeruginosa

Skin infection with blue-green pus, often from burns.

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Buruli Ulcer

Deep, damaging skin ulcers caused by Mycobacterium ulcerans.

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Comedonal Acne

Mild acne with blocked sebum channels.

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Inflammatory Acne

Acne with Gram-positive, anaerobic Propionibacterium.

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Nodular Cystic Acne

Severe acne with nodular cysts; treated with isotretinoin.

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Warts

Skin growths caused by papillomaviruses.

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Smallpox (Variola)

Viral disease with high mortality from orthopox virus.

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Chickenpox

Transmitted via respiratory route; latent in ganglia.

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Shingles

Reactivation of Chickenpox; moves along peripheral nerves and live attenuated vaccine to help

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Herpes Simplex

Vesicles on lips; latent in trigeminal nerve ganglia (HSV-1 & 2).

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Measles (Rubeola)

Measles virus, transmitted by respiratory route, prevented by vaccination; leads to rash and Koplik's spots.

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Rubella

German measles with Macular rash & fever; congenital rubella syndrome.

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Fifth Disease

Erythema infectiosum; Human parvovirus B19 produces mild flu-like symptoms and facial rash.

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Roseola

Caused by human herpesvirus 6 (HHV-6) and 7 (HHV-7); results in a high fever and rash.

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Dermatomycoses

Fungal infections also known as tineas or ringworm; metabolize Keratin.

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Trichophyton

Fungal infection of hair, skin, and nails.

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Epidermophyton

Fungal infection of skin and nails.

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Microsporum

Fungal infection of hair and skin.

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Sporotrichosis

Most common U.S. subcutaneous fungal disease; enters puncture wound; potassium iodide (KI) treatment.

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Candidiasis

Fungal disease from suppressed bacteria with antibiotics; occurs in skin, mucous membranes; thrush.

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Scabies

Parasitic infestation where sarcoptes scabiei burrows in the skin and lays eggs; use topical insecticides.

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Pediculosis

Parasitic infection with head or body lice; treat with topical insecticides.

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Conjunctivitis

eye inflammation of the conjunctiva

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Ophthalmia neonatorum

Caused by Neisseria gonorrhoeae. Transmitted to a newborn's eyes during passage through the birth canal.

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Chlamydia trachomatis

Causes inclusion conjunctivitis, or chlamydial conjunctivitis

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Chlamydia trachomatis

Causes trachoma, is a leading cause of blindness worldwide.

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Keratitis

Inflammation of the cornea

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Herpetic keratitis

Caused by herpes simplex virus 1 (HSV-1). Infects cornea and may cause blindness

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Acanthamoeba keratitis

Transmitted via water and is associated with unsanitary contact lenses

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Study Notes

Structure and Function of the Skin

  • The skin and mucous membranes structure are described along with how pathogens can invade it.

The Structure of Human Skin

  • Perspiration and sebum contain nutrients
  • Salt inhibits microbes
  • Lysozyme hydrolyzes peptidoglycan
  • Fatty acids inhibit some pathogens

Mucous Membranes

  • Line body cavities
  • Epithelial cells attach to an extracellular matrix
  • Cells secrete mucus
  • Often acidic
  • Some cells have cilia
  • In eyes, tears wash away with lysozyme

Normal Microbiota of the Skin

  • Examples of normal skin microbiota are provided with their general locations and ecological roles.
  • Gram-positive, salt-tolerant bacteria exist on the skin
    • Staphylococci
    • Micrococci
    • Diphtheroids
  • Grow on oils
  • Aerobes exist on the surface
    • Corynebacterium xerosis
  • Anaerobes exist in hair follicles
    • Propionibacterium acnes
  • Yeast is part of the normal Microbiota of the Skin
    • Malassezia furfur

Microbial Diseases of the Skin

  • Exanthem: Skin rash arising from another focus of the infection
  • Enanthem: Mucous membrane rash arising from another focus of the infection

Bacterial Diseases of the Skin

  • Staphylococci are differentiated from streptococci, with skin infections caused by each listed
  • The causative agent, mode of transmission, and clinical symptoms of Pseudomonas dermatitis, otitis externa, acne, and Buruli ulcer are listed.

Staphylococcal Skin Infections

  • Staphylococcus epidermidis are gram-positive cocci and coagulase-negative
  • Staphylococcus aureus are gram-positive cocci and coagulase-positive
  • Folliculitis: Infections of the hair follicles
  • Sty: Folliculitis of an eyelash
  • Furuncle: Abscess; pus surrounded by inflamed tissue
  • Carbuncle: Inflammation of tissue under the skin
  • Impetigo: crusting (nonbullous) sores, spread by autoinoculation.

Staphylococcus aureus

  • This bacteria is antibiotic resistant
  • Leukocidin is present
  • It resists opsonization
  • Survives in phagolysosome
  • Lysozyme resistant
  • Exfoliative toxin exists
  • Produces a Superantigen

Scalded Skin Syndrome

  • Toxic shock syndrome (TSS) produces toxic shock syndrome toxin 1.
  • Scalded skin syndrome includes bullous impetigo and impetigo of the newborn

Streptococcal Skin Infections

  • Streptococcus pyogenes is a Group A beta-hemolytic streptococci
  • Produces Hemolysins
  • Hyaluronidase is present
  • Stretolysins is produced
  • Produces M proteins
  • Necrotizing fasciitis
  • Erysipelas

Invasive Group A Streptococcal

  • Exotoxin A, superantigen is present

Streptococcal Toxic Shock Syndrome

  • M proteins are present
  • Complex with fibrinogen
  • Binds to neutrophils
  • Activates neutrophils
  • Release of damaging enzymes
  • Causes Shock and organ damage

Infections by Pseudomonads

  • Pseudomonas aeruginosa, a gram-negative, aerobic rod creates pyocyanin which produces a blue-green pus
  • Pseudomonas dermatitis
  • Otitis externa, or “swimmer’s ear”
  • Post-burn infections
  • Opportunistic

Buruli Ulcer

  • Caused by Mycobacterium ulcerans
  • It causes deep, damaging ulcers
  • Exceeds incidence of leprosy

Classifications of Acne

  • Comedonal (mild) acne
  • Inflammatory (moderate) acne
  • Nodular cystic (severe) acne

Comedonal Acne

  • Mild
    • Sebum channels blocked with shed cells
  • Treatment
    • Topical agents are used
    • Salicyclic acid preparations
    • Retinoids
    • Adapalene

Inflammatory Acne

  • Propionibacterium acnes is a Gram-positive, anaerobic rod
  • Treatment
    • Preventing sebum formation through isotretinoin
    • Antibiotics
    • Benzoyl peroxide to loosen clogged follicles
    • Visible (blue) light which kills P. acnes

Nodular Cystic Acne

  • Severe
  • Treatment
    • Isotretinoin

Viral Diseases of the Skin

  • Causative agent, mode of transmission, and clinical symptoms are all listed
    • Warts, smallpox, monkeypox, chickenpox, shingles, cold sores, measles, rubella, fifth disease, and roseola.

Warts

  • Papillomaviruses cause warts
  • Treatment
    • Removal - Cryotherapy - Electrodesiccation (most common) - Salicylic acid
    • Imiquimod stimulates interferon production
    • Bleomycin (anti-viral)

Poxviruses

  • Smallpox (variola) is caused by the smallpox virus (orthopox virus)
    • Variola major has 20% mortality
    • Variola minor has <1% mortality
  • Eradicated by vaccination
  • Monkeypox
    • Prevention is acheived through smallpox vaccination

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