Cutaneous Microbiology

Question 1

At what point does the presence of microorganisms on the skin go from colonization to infection?

Answer 1

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

Question 2

Name two risk factors for greater rate of skin infection.

Answer 2

disruption of normal skin barrier (trauma, inflammatory disease and maceration) and delayed wound healing (immunosuppression, diabetes, renal failure and advanced age)

Question 3

What are the clinical presentation of impetigo?

Answer 3

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)

Question 4

What are the causes and treatment of impetigo?

Answer 4

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)

Question 5

Compare the clinical presentation of ecthyma to that of impetigo

Answer 5

deeper infection by same bacteria causing ulceration and thick crust (heals with scar)

Question 6

Distinguish an access, furuncle and carbuncle.

Answer 6

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

Question 7

What is the most common microorganism responsible for an abscess? What is standard treatment?

Answer 7

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)

Question 8

What is the clinical presentation of erysipelas? What bacteria causes this infection and how is it treated?

Answer 8

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

Question 9

What is the clinical presentation of erythrasma? What bacteria causes this infection?

Answer 9

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)

Question 10

Tinea is caused by which genus (geni?) of dermatophytes?

Answer 10

trichophyton, epidermophyton, microsporum

Question 11

Which are the 3 sources of tina spread?

Answer 11

anthropophilli (human), zoophillic (animal and frequently most severe, can cause kerion) and geophilic (fomites)

Question 12

Name 5 classifications of tina based on body site.

Answer 12

capitis (scalp), cruris (groin- spares the scrotum) and pedis (feet), corporis (body) unguim (nails)

Question 13

How does tinea appear under KOH examination?

Answer 13

long septa, no spores

Question 14

How do you treat a dermatophyte infection?

Answer 14

with topical antifungals if focal an with oral antifungals if widespread or involving hair follicles

Question 15

What microorganism causes pityriasis versicolor? What does this look like under KOH examination

Answer 15

malassezia furfur, transmitted by direct contact, appears as spaghetti and meatballs, both hyphae and spores

Question 16

How is ptiyriasis versicolor treated?

Answer 16

with antifungals (with systemic treatment must weigh the concern of hepatotoxicity)

Question 17

How is seborrheic dermatitis connected to fungal infection?

Answer 17

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

Question 18

What is the clinical presentation of candidiasis?

Answer 18

affects the skin folds causing intertrigo (erythematous patches with satellite papules and pustules, maceration and associated with foul odor (may involve the scrotum)

Question 19

What is the cause/tx of candidiasis?

Answer 19

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

Question 20

What are the presenting signs of a herpes simplex virus infection?

Answer 20

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

Question 21

What test would you use to confirm a diagnosis of herpes? What are the two types of herpes simplex virus?

Answer 21

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

Question 22

What is treatment for HSV?

Answer 22

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)

Question 23

What is erythema multiform?

Answer 23

is a recurrent reaction to HSV resulting in targeted lesions and affecting the skin and oral mucosa (self-limiting infection, only treat the symptoms)

Question 24

What is the clinical presentation for varicella zoster virus?

Answer 24

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

Question 25

What is the mechanism of human pailloma virus?

Answer 25

infects the basal keratinocytes (cerruca vulgaris in skin, condyloma acuminata in genital mucosa)

Question 26

Name the strains of HPV that are likely to lead to oral, cervical, vaginal, vulvar or penile cancers? Which are “low risk”.

Answer 26

high risk 16, 18, 33 and 35

low risk 6, and 11 (constitute 90% of genital worts)

Question 27

Name 4 ways to treat worts.

Answer 27

salicylic acid, cryotherapy, immunotherapy (application of topical irritant), surgical removal (electrodessication or laser ablation)

** vaccine can reduce infection with high risk strains

Question 28

What is the clinical presentation of molluscum contagious? How do you treat molluscum?

Answer 28

umbilicated papule, resolves spontaneously but can be removed by destructive methods

Question 29

What is the clinical presentation of erythema infectious?

Answer 29

prodrome of fever, HA, arthralgias, aplastic crisis and risk of hydrops fettles in adults, spread buy respiratory secretions of Parvovirus B19 AKA 5th’s disease

Question 30

Describe the location and parasite involved in scabies infection.

Answer 30

sarcoptes scabei infect the stratum corneum and subsist off of a blood meal

Question 31

What is the clinical test to confirm scabies?

Answer 31

mineral oil prep of a end of burrow biopsy, looking for mite, eggs or mite poop

Question 32

How do you treat scabies?

Answer 32

apply an anti-scabetic from the neck down overnight and rinse in the morning, oral anti scabetics can also be administered, and treatment of bedding and clothing is important