Dermatologic Infections and Infestations Flashcards
Whats the most common superficial bacterial infection in kids? What agents cause this?
Impetigo
streptococci
Staphylococcus aureus
What are the two kinds of impetigo and which bacteria usually cause them?
Non-bullous (70-80% of impetigos)
- impetigo contagiosa is usually streptococcal infections
- staph is most common cause of both
Bullous: staph
How does non-bullous impetigo usually present in the clinic?
primary lesion with a “honey-colored” yellow crust on the face (nose of adults)
Skin to skin contact
What causes bullous impetigo?
Staph makes toxin that affects desmosones of keratinocytes, making blisters all over the skin with layer of pus
Who is susceptible to cellulitis?
– Very young – Elderly – Immunocompromised – Intravenous drug users – Patients with chronic ulcers
What do you call the variant of cellulitis that is confined to the face? How does it present?
Erysipelas (St. Anthony’s fire)
-erythema that is well demarcated (cliff-drop border), with regional lymphadenopathy, Incubation period- 2 to 5 days
What bacteria are most associated with cellulitis?
β-hemolytic streptococci (Streptococcus pyogenes), Staphylococcus aureus, and Haemophilus influenzae (in children)
Where and how does cellulitis usually occur?
Usually in extremities from some trauma (ie: you cut your foot)
What are common clinical presentations of cellulitis?
Primary lesion- tender ill-defined area of painful erythema with variable induration,
Lymphatic streaking- common
Lymphadenopathy- variable
Diagnose with CULTURE (more sensitive) on leading edge
Where do you find dermatophytes and name the three kinds?
“they eat keratin”- nails, skin, hair
- Epidermophyton
- Microsporum
- Trichophyton
Which dermatophyte causes “socks and jocks” infections (athletes foot, jock itch)
epidermophyton
Which dermatophyte gives tine corporis to kids from a cat
Microsporum
*also it flouresces
Which dermatophyte is the most common to infect human?
Trichophyton
Where does the term “ring-worm” come from?
Tinea (capitis, faciei, barbae, corporis, pedis)
- fungus that eats keratinocytes and spreads out in circle to make a ring-shaped plaque, alopecia, scaling in scalp
What is “kerion” in relation to tinea?
It is an inflammatory response due to the fungus
T/F: use topical steroids with fungus
False
You have to use systemic, because topical will suppress it locally and fungus will go deeper. Or topical fungicides- naftifine (think nasty-feet)
What is candida?
A normal fluora of skin that can infect skin and mucous membranes in those with diabetes, occlusion, use of corticosteroids, or in patients treated with broad-
spectrum antibiotics
These eat glucose- not skin- so the infection is deeper
List different candida infections
Thrush: white scaly stuff in mouth, common with HIV
Perleche: sores in corner of mouth
interdigitalis blastomycetica: white sores in between fingers
Candida diaper dermatitis: red rash on babies
What causes tinea versicolor and who gets it?
Yeast (Pityrosporum orbiculare)
In post-puberty patients
Clinical characteristics of tinea versicolor?
- Usually on trunk
- Primary lesion- asymptomatic, tan- colored subtly scaly macule or patch (scales from scratching)
- Hypopigmented variant
- “spaghetti and meatballs” under histology
What are clinical characteristics of scabies? What causes it?
Sarcoptes scabiei parasite
- soft skin distribution
- itching- nocturnal accentuation
- Erythematous papules
- Erythematous burrows- variable scale
What are clinical characteristics of lice?
- Head: Limited to scalp with the area behind the ears in the nape of the neck being the areas most commonly affected -Symptoms- intense pruritus (itch), Erythema, scale, and secondary infection commonly present
- Eggs attached to hair shafts or clothes if on body
- crab lice: genital area
What is a Tzanck smear and what does it look for?
is scraping of an ulcer base to look for multinucelated keratinocytes and large vesicular nuclei in keratinocytes
Test for HSV (herpes)
What does KOH prep look for?
scrape off border, dissolves epithelial cell and cell wall making it easier to identify differentiate Candida, dermatophyte, fungus, etc.
What does a mineral oil (wet prep) look for?
Scabies
a small drop of mineral oil is placed on the skin in gently scraped and examined under a microscope for evidence of infestation (mites, eggs, or feces)
What does a gram stain test for?
Impetigo & Cellulitis
sample of crust or fluid from intact bullae leading edge
What does the Wood’s light exam do?
A Wood’s lamp examination is a procedure that uses transillumination (light) to detect bacterial or fungal skin infections- tinea capitis, tinea versicolor
