SM_263a: Bacterial and Fungal Skin Infections Flashcards
Superficial cutaneous fungal infections are limited to the ____ and are caused by ____, ____, and ____
Superficial cutaneous fungal infections are limited to the epidermis and are caused by dermatophytes, Malassezia spp., and Candida spp.
(dermatophytes include Trichophyton spp., Microsporum spp., and Epidermophyton spp. and infect keratinzed tissues - stratum corneum, nail, hair)
Arthrospores inside hair shafts (endothrix) on KOH stain are indicative of ____
Arthrospores inside hair shafts (endothrix) on KOH stain are indicative of tinea capitis
Tinea capitis is spread through ____
Tinea capitis is spread through direct contact with animals, humans, and fomites
Describe tinea capitis variants
Tinea capitis variants
- Non-inflammatory: seborrheic, black dot
- Inflammatory: kerion (painful inflammatory boggy mass w/ broken hair follicles, risk of scarring)
Tinea capitis is treated ____
Tinea capitis is treated systemically (griseofulvin, terbenafine)
(topical agents are ineffective)
Branched septate hyphae on KOH stain are indicative of ____
Branched septate hyphae on KOH stain are indicative of tinea corporis
(parallel throughout entire length)
Tinea pedis is known as ____
Tinea pedis is known as athlete’s foot
- May have fine scales on sole and between toes, vesicles often appear on bottom / sides of foot
- Interdigital type: most common, presents with scaling and redness between toes and may have associated maceration
- Mocassin type: sharply marginated scale, distributed along lateral borders of feet, heels, and soles
- Vesicobullous type
____ is a potential complication of tinea pedis and involves ____
Onychomycosis is a potential complication of tinea pedis and involves chronic fungal infection of nailbed
Onychomycosis should be ____ then ____ and responds poorly to ____
Onychomycosis should be proved then treated and responds poorly to topical antifungals
(identification of fungus in affected nail via positive KOH prep or nail biopsy is necessary before treatment)
This is ____
This is tinea corporis
(annular lesion w/ central clearing, caused by T. rubrum / M. canis / T. mentagrophytes)
Tinea corporis is also known as ____ and refers to ____
Tinea corporis is also known as ringworm and refers to dermatophytosis of the skin of the body
(itchy, the margin of lesion is most active / central area tends to heal, scraping should be taken from red scaly margin for KOH exam)
This is ____
This is tinea versicolor
Tinea versicolor is ____ pattern on KOH prep
Tinea versicolor is spaghetti and meatball pattern in KOH prep
Describe tinea versicolor
Tinea versicolor
- Not a dermatophytosis
- Caused by overgrowth of Malassezia: lipophilic yeast that is a normal resident in keratin of the skin and hair follicles
- Tends to recur annually in the summer months
- Characterized by variable colored, often rounded, patches - most common trunk
- Visible scale often not present but seen when rubbed with finger or scalpel blade
Visible scale not present but scale readily seen when rubbed with finger / blade refers to ____
Visible scale not present but scale readily seen when rubbed with finger / blade refers to tinea versicolor
Describe tinea versicolor treatment
Tinea versicolor
- 2.5% selenium sulfide shampoo
- Topical antifungals daily for 2 weeks
- Oral antifungals for recalcitrant disease
- Relapse / recurrence is the rule
This is ____
This is diaper candidiasis
(beefy red plaques with very fine white scale in groin area, skin creases involves, satellite papules and pustules noted on inner thigh and abdomen)
Diaper candidiasis is characterized by ____ and does not improve with ____
Diaper candidiasis is characterized by satellitle papules and pustules and does not improve with application of barrier creams
(irritant diaper dermatitis is erythema, erosion, spares skin folds, severe cases may show ulcerated papules and islands of re-epithelialization)
Describe pathogenesis of diaper candidiiasis
Diaper candidiasis pathogenesis
- Urease enzymes present in feces release ammonia from urine
- Acute irritant effect
- Disruption of epidermal barrier
- Entry of Candida (present in feces)
(wet and dirty diapers that are not changed on a regular basis contribute to development of diaper dermatitis)
Candidal intertrigo affects ____, commonly affects ____ patients, manifests as ____ on KOH exam, and is treated with ____
Candidal intertrigo affects large skin folds, commonly affects obese patients, manifests as pseudohyphae, and is treated with antifungal agents
(prevention is keep intertriginous areas dry / cool / clean and encouraging weight loss for obese patients)
Sporotrichosis is ____ infection caused by ____ growing on ____ and manifests as a ____
Sporotrichosis is a subcutaenous infection caused by Sporothrix Schenickii growing on decaying vegetable matter and manifests as a dermal nodule then chain of secondary nodules on the course of lymphatics
Broad based budding yeast is ___ and can manifest on skin as a result of ____
Broad based budding yeast is blastomycosis and can manifest on skin as a result of dissemination from lungs
(Great Lakes region in the US, thick-walled rounded refractile spheres)
Bullous impetigo is a bacterial infection caused by ____ and results from a ____
Bullous impetigo is a bacterial infection caused by Gram positive bacteria (Staphylococcus aureus) and results from a secreted exotoxin
(disrupts desmogleins in desmosomes -> causes blisters)
Staphylococcal scalded skin syndrome is ____
Staphylococcal scalded skin syndrome is when a focus of infection secretes toxin that bind to desmoglein-1 in the granular cell layer into the blood, leading to widespread blisters
(not a skin infection)
Staphylococcal scalded skin syndrome is caused by ____ that bind to ____ in the ____ cell layer and produce ____
Staphylococcal scalded skin syndrome is caused by 2 endotoxins that bind to desmoglein-1 in the granular cell layer and produce blistering
____ and ____ are at risk for staphylococcal scalded skin syndrome
Kids < 5 years and adults with renal disease are at risk for staphylococcal scalded skin syndrome
Wound cultures from erosions are ____ in staphylococcal scalded skin syndrome
Wound cultures from erosions are negative in staphylococcal scalded skin syndrome
Scarlet fever is a ____ caused by ____
Scarlet fever is an exotoxin-triggered reaction with cutaneous manifestations caused by Group A Streptococcal pyrogenic exotoxins
Scarlet fever usually occurs in ages ___
Scarlet fever usually occurs in ages 2-10
(rarely in adults)
Scarlet fever is characterized by ____, diagnosed by ____, and treated using ____
Scarlet fever is characterized by exanthem followed by desquamation beginning at face and ending with hands and feet, diagnosed by positive strep culture from throat, treated using penicillin
Cellulitis is ____, is caused by ____, and is commonly found on ____
Cellulitis is spreading erythematous tender plaque, is caused by Group A Strep / Staphylococcus aureus infection of the dermis, and is commonly found on the lower leg
Cellulitis treatment involves ____
Cellulitis treatment involves beginning antibiotics immediately for coverage for Gram positive bacteria
Erysipelas is ____
Erysipelas is superficial cellulitis with marked dermal lymphatic involvement, causing skin to be edematous or raised
(lower extremities and face, Group A strep)
Abscess is ____
Abscess is collection of pus within dermis and deeper tissues
(painful / tender / fluctuant and erythematous nodules, often surmounted by a pustule and surrounded by a rim of erythematous edema, spontaneous drainage of purulent material may occur)
Abscesses are treated with ____
Abscesses are treated with incision and drainage
Folliculitis is most often caused by ____
Folliculitis is most often caused by Staphylococcus aureus
(multiple small papules / pustules on an erythematous base that are pierced by a central hair although the hair may not always be visualized)
Furuncle is ___
Furuncle is acute, round, tender, circumscribed perifollicular abscess that generally ends in central suppuration
(usually caused by Staphylococcus aureus)
Carbuncle is ____
Carbuncle is coalescence of several inflammed follicles into a single inflammatory mass with purulent drainage from multiple follicles
(usually caused by Staphylococcus aureus)
Describa anthrax
Anthrax
- Caused by Bacillus anthracis
- Large, boxcar shaped, Gram-positive, non-motile, spore-forming bacterial rod
- Endemic to wild and domestic animals
- Inhalational, gastrointestinal, and cutaneous
Cutaneous anthrax is characterized by ____ and ____
Cutaneous anthrax is characterized by central ulceration and black eschar
Secondary syphilis is similar to eruption of pityriasis rosea except there are additional ____ and ____
Secondary syphilis is similar to eruption of pityriasis rosea except there are additional lymphadenopathy and palm / sole involvement
(lesions contain spirochetes so wear gloves, Treponema palldium)
Syphilis testing involves ____ and is treated with ____
Syphilis testing involves RPR with prozone and is treated with intramuscular penicillin
(prozone phenomenon on agglutination tests: antigen / antibody mismatch such that there is so much excess antibody that it clumps and leads to false negative, need to rerun test as serial serum dilutions)
TB cutaneously presents as ___ or ___
TB cutaneously presents as lupus vulgaris or scrofuloderma
(scrofuloderma: cold abscess and breakdown of overlying skin)
Mycobacteria marinum presents as ____
Mycobacteria marinum presents as fish tank granuloma
Mycobacterium leprosy is ___
Mycobacterium leprosy is chronic granulomatous infection especially of skin and nerves (leprosy / Hansen’s disease)
