Cutaneous Microbiology Flashcards
At what point does the presence of microorganisms on the skin go from colonization to infection?
when the presence of those microorganisms in numbers that interrupt normal cellular functioning, when taking a culture it is important to remember the greater context of location and type of microorganism
Name two risk factors for greater rate of skin infection.
disruption of normal skin barrier (trauma, inflammatory disease and maceration) and delayed wound healing (immunosuppression, diabetes, renal failure and advanced age)
What are the clinical presentation of impetigo?
non-bullous: honey-colored crusting, non healing wound (staph aureus> strep pyrogenes)
bullous: prodrome of malaise, fever, diarrhea, flaccid bullae (bothers adults more than children) (staph aureus phage II, type 71)
What are the causes and treatment of impetigo?
toxins produced by staph attack desmoglein 1 and cause cells to become unconnected
treatment: cover the affected site to prevent spread and administration of topical or oral antibiotics (generalized disease or high risk patients)
Compare the clinical presentation of ecthyma to that of impetigo
deeper infection by same bacteria causing ulceration and thick crust (heals with scar)
Distinguish an access, furuncle and carbuncle.
an abscess is a collection of pus with a surrounding fibrous reaction a furuncle involves a hair follicle and a carbuncle a collection of furuncles
What is the most common microorganism responsible for an abscess? What is standard treatment?
staph aureus is most common, tx. includes warm compresses, incision and drainage and oral antibiotics (perinasal location, large and recurrent, cellullitis or failure to respond to warm compress)
What is the clinical presentation of erysipelas? What bacteria causes this infection and how is it treated?
normally present in elderly patients with a erythmatous patch with a sharply demarcated border; accompanied with fever, chills and malaise. caused by streph progenies and is treated with oral antibiotics
What is the clinical presentation of erythrasma? What bacteria causes this infection?
usually asymptomatic, located in skin folds which fluoresce coral red under a wood’s lamp. caused by corynebacterium minutissiumum (tx with antibiotic or anti fungal for their anti-inflammatory “azoles” properties)
Tinea is caused by which genus (geni?) of dermatophytes?
trichophyton, epidermophyton, microsporum
Which are the 3 sources of tina spread?
anthropophilli (human), zoophillic (animal and frequently most severe, can cause kerion) and geophilic (fomites)
Name 5 classifications of tina based on body site.
capitis (scalp), cruris (groin- spares the scrotum) and pedis (feet), corporis (body) unguim (nails)
How does tinea appear under KOH examination?
long septa, no spores
How do you treat a dermatophyte infection?
with topical antifungals if focal an with oral antifungals if widespread or involving hair follicles
What microorganism causes pityriasis versicolor? What does this look like under KOH examination
malassezia furfur, transmitted by direct contact, appears as spaghetti and meatballs, both hyphae and spores
How is ptiyriasis versicolor treated?
with antifungals (with systemic treatment must weigh the concern of hepatotoxicity)
How is seborrheic dermatitis connected to fungal infection?
seborrheic dermatitis etiology is unknown but it is possibly connected to pityrosporum yeast infection (risk factors include HIV or parkinson’s disease); it treated with topical antifungals, anti seborrheic shampoo (i.e. selenium sulfide) and if no improvement, low potency topical steroid
What is the clinical presentation of candidiasis?
affects the skin folds causing intertrigo (erythematous patches with satellite papules and pustules, maceration and associated with foul odor (may involve the scrotum)
What is the cause/tx of candidiasis?
caused by a yeast (candida albicans) and is common with humid weather. it is treated with topical anifungals (not terbinafine) and also barrier pastes like zinc oxide
What are the presenting signs of a herpes simplex virus infection?
painful uniform vesicles on a red base which becomes eroded , hemmorrhagic crust with a scalloped border due to coalescence of vesicles and palpable lymph nodes, maybe accompanied by a prodrome of tingling and pain; there is a high incidence of subclincal infection
What test would you use to confirm a diagnosis of herpes? What are the two types of herpes simplex virus?
Tzanck prep confirms diagnosis with multinucleate giant cellsand the two given types ar HSV1 and HSV2, can be monitored with serologic tests for HSV1 and 2 antibodies
What is treatment for HSV?
initiate oral antivirals at the first sign of an outbreak, for more frequent outbreaks can use a daily suppressive dose (can reduce transmission of HSV in discordant couples)
What is erythema multiform?
is a recurrent reaction to HSV resulting in targeted lesions and affecting the skin and oral mucosa (self-limiting infection, only treat the symptoms)
What is the clinical presentation for varicella zoster virus?
painful vesicles on an erythematous base the follow unilateral dermatomal distribution and lymphadenopahty in people with a history of primary varicella (chicken pox) accompanied by malaise, tx with oral antivirals
