(10-24) Skin Infections Flashcards
1. Describe the importance of skin glands in health and disease. 2. List the three major groups of microorganisms making up the normal flora of the skin. 3. Describe the role of normal skin flora in health and disease. 4. List the skin diseases caused by: Staphylococcus aureus, Streptococcus pyogenes 5. Give the causative agent for the following diseases: Streptococcal impetigo, Chickenpox, Shingles, Superficial cutaneous mycoses 6. Give the major pathogenic and symptomatic features of the
Name 6 anatomical features of human skin.
- Epidermis
- Dermis
- Sweat glands
- Hair follicle
- Sebaceous glands
- Tiny sensory neurons
What are the 3 groups that most skin flora can be categorized into?
1. Diphtheroids ~ ex. Propionibacterium acnes 2. Staphylococci ~ Staphylococcus epidermidis 3. Yeasts
Which bacterium causes hair follicle infections?
Staphylococcus aureus
Which bacterium causes Scalded Skin Syndrome?
Staphylococcus aureus
Which 2 bacterial skin diseases does Staphylococcus aureus cause?
- Hair Follicle Infections
2. Scalded Skin Syndrome
Which bacterium causes Impetigo?
Streptococcus pyogenes
Which bacterium causes Rocky Mountain Spotted Fever?
Rickettsia rickettsii
Which bacterium causes Lyme Disease?
Borrelia burgdorferi
Which is more virulent: S. aureus or S. epidermidis?
S. aureus
In which 2 ways can S. aureus avoid host defenses?
- Its capsule impedes phagocytosis
2. It produces numerous enzymes that degrade tissue
Why aren’t S. aureus infections treated with penicillin?
90% of S. aureus strains are resistant to penicillin.
How can a S. aureus infection be treated?
- Drain the boil
2. Antibiotics
What is Streptococcal Impetigo?
A superficial skin infection involving patches of epidermis tissue just below the outer layer
Why is S. pyogenes referred to as Group A Strep?
Due to presence of Group A cell wall polysaccharide.
What does Streptococcal Impetigo result from, and how does it develop?
- Results from infection of an insect bite, scrape, or other nonapparent wound
- Blisters develop, then break releasing plasma that dries to a yellowing crust
Describe the shape and cell wall structural characteristics of S. pyogenes.
S. pyogenes is a Gram-positive, β-hemolytic cocci.
Give one example to explain how the extracellular products produced by S. pyogenes may aid its virulence.
Some strains produce protease that degrade tissue rapidly → “flesh-eating bacteria.”
What is the treatment for Streptococcal Impetigo?
Penicillin
Which virus causes Chicken Pox?
Varicella-zoster virus
Which virus causes Measles?
Rubeola virus
Which virus causes German Measles?
Rubella virus
Which virus causes Fifth Disease?
Parvovirus B-19
Which virus causes Roseola?
Herpesvirus type 6
How is Varicella transmitted?
By respiratory secretions and skin lesions.
Is the presence of Varicella increasing or decreasing overall, and why?
Incidence is declining due to effective vaccine.
Describe the pathogenesis of Varicella in 5 steps.
- Virus enters through respiratory route
- Replicates and moves to the skin via blood stream
- Infects living layers of skin and moves to adjacent cells creating skin lesions
- Infected cells swell and lyse
- Released virus infects sensory nerves
What is the latent virus produced by Varicella virus?
Shingles
How long is the viral incubation period for Varicella?
Approximately 2 weeks
When is Varicella infective?
Varicella is infective from 1 - 2 days before rash until blisters crust over.
During which seasons do the incidences of Varicella increase?
Varicella incidences increases in winter and spring due to close contact.
What is another name for Shingles?
Herpes Zoster
What aspect of Herpes Zoster is significant with regards to epidemiology?
Persistence in the body allows survival of viral populations.
Who is most likely to develop Shingles, and why?
- Elderly or immunocompromised
2. Correlates with decline in cell mediated immunity
Which area of the body are Shingles lesions usually restricted to?
Lesions are usually restricted to area supplied by the sensory nerve.
How are Shingles infections dealt with by the immune system?
- Inflammatory reaction occurs
- Memory cells (secondary response) respond
- Shingles disappears
[Pain can persist.]
What are Dermatophytes?
Molds that invade human skin, hair, or nails.
What do Dermatophytes use as nutrition?
Dissolved keratin from the host’s epidermis.
Give 3 examples of Superficial Cutaneous Mycoses.
- Jock itch
- Athlete’s foot
- Ringworm
How can Superficial Cutaneous Mycoses be prevented and treated?
- Prevention: cleanliness and dryness
2. Treatment: anti-fungal medications
The microorganisms that cause Superficial Cutaneous Mycoses are called what?
Molds termed Dermatophytes
Which bacterium maintains the balance of normal flora and plays a vital role in limiting colonization by pathogens?
Staphylococcus
