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Dermatology 1 > Bacterial Skin Infections > Flashcards

Bacterial Skin Infections Flashcards

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Dermatology Board Prep flashcards
1
Q

3 major factors for development of bacterial infection

A

(1) the portal of entry and skin barrier function
(2) the host defenses and inflammatory response to microbial invasion,
(3) the pathogenic properties of the organism

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2
Q

Primary infection

A
  • Invasion of normal skin by usually a single speciesbacteria.
  • Treatment of bacterial pathogen, cures the lesion
  • Ex: Impetigo, erysipelas, furunculosis
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3
Q

Secondary infection

A
  • Develop in areas of already damaged skin
  • Bacteria present did not produce underlying skin disorder but may aggravate and prolong the disease
  • Usually mixture of organisms
  • Ex: Atopic dermatitis with secondary infection
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4
Q

What are the major pathogens of bacterial skin infections?

A

S. aureus or group A Streptococcus

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5
Q

Define impetigo

A
  • Common, highly contagious
  • Superficial skin infection (Pyoderma)
  • Bullous or non-bullous: non-bullous is majority**
  • Seen in children and adults
  • Limited to epidermis
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6
Q

What organism causes Impetigo?

A
  • S. aureus

- GAS

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7
Q

Nonbullous impetigo clinical presentation

A
  • red macule becomes a vesicle which ruptures, forming erosion with honey-colored crusting (more prominent than bullous type)
  • usually face or extremities
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8
Q

Bullous impetigo clinical presentation

A
  • vesicle progresses to flaccid bulla
  • no surrounding erythema.
  • bulla ruptures forming honey-colored crust
  • favors intertriginous areas
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9
Q

Dx of impetigo

A

Gram stain or Bacterial cultures can be obtained but not necessary

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10
Q

Tx of impetigo

A

-Antibacterial wash

Localized impetigo can be treated with topical medications including:

  • Mupirocin (Bactroban) ointment
  • Retapamulin (Altabax) ointment
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11
Q

Other tx of impetigo

A
  • more widespread impetigo may require oral antibiotics, such as first-generation cephalosporins, dicloxacillin, amoxicillin/clavunate, or azithromycin
  • refer for severe or persistent disease that does not respond to therapy
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12
Q

Define folliculitis

A
  • infection of hair follicle with +/- pus in the ostium of follicle
  • begins in the upper portion of the hair follicle
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13
Q

PE of folliculitis

A
  • follicular papule, pustule, or crust at the follicular infundibulum
  • can extend deeper into the entire length of the follicle (sycosis)
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14
Q

Causes of folliculitis

A

1 is always bacteria - staph or strep (mainly staph)

Bacteria, fungi, virus and mites

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15
Q

S/sx of folliculitis

A

Usually nontender or slightly tender, may be pruritic

*Can progress to abscess or furuncle formation

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16
Q

Predisposing factors of folliculitis

A
  • shaving hairy regions
  • occlusion of hair-bearing areas
  • topical corticosteroid preparations
  • diabetes mellitus
  • and immunosuppression
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17
Q

Organisms causing folliculitis

-bacteria

A

S. aureus;Pseudomonas aeruginosa(hot-tub)

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18
Q

Organisms causing folliculitis

-viral

A

Herpetic, molluscum contagiosum

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19
Q

Organisms causing folliculitis

-fungal

A

Candida, Malassezia, dermatophytes

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20
Q

Organisms causing folliculitis

-other

A

Demodex

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21
Q

Dx of folliculitis

A
  • diagnosis made clinically
  • cultures from intact pustules may isolate the causative organism
  • skin scrapings may identify folliculitis caused bydemodexorpityrosporum
22
Q

Tx of bacterial folliculitis

-mild

A

mild cases may be managed by topical disinfectant skin washes (eg, benzoyl peroxide, Dial soap, benzalkonium chloride, chlorhexidine, and bleach baths) +/- topical antibiotic (erythromycin, clindamycin)

23
Q

Tx of bacterial folliculitis

-mod or severe

A

moderate or severe cases often requires 10 to 15 days of the appropriate oral antibiotic- dicloxacillin, amoxicillin, cephalosporins anddoxycycline- usually for 7 to 10 days

*10 days is normal treatment time

24
Q

Hot-tub folliculitis is caused by…

A

Pseudomonas Aeruginosa

-following immersion in contaminated spa/pool water

25
Q

PE of hot-tub folliculitis

A
  • follicular-based papules and pustules of the trunk and lower extremities
  • areas covered by bathing suits and axillae more prone
26
Q

S/sx of hot-tub folliculitis

A

Fever, lymphadenopathy, and otitis externa (swimmer’s ear) may also rarely be associated with hot tub folliculitis

27
Q

Tx of hot-tub folliculitis

A
  • typically self-resolving, within 1 to 2 weeks, as long as one stays out of contaminated water
  • severe cases: oral ciprofloxacin 500mg orally twice daily for 7 days
28
Q

Define furuncle

A

AKA “boil”

  • deep-seated inflammatory nodule that develops around a hair follicle
  • arise in hair-bearing sites, particularly in regions subject to friction, occlusion, and perspiration, such as the neck, face, axillae, and buttocks
29
Q

Furuncle etiology

A
  • Often occur in the setting of staphylococcal folliculitis
  • Majority of patients otherwise healthy
  • Often more extensive with diabetes
30
Q

Organism that causes furuncle

A

Staphylococcus aureus (SA) is the MCC - Methicillin sensitive (MSSA) or methicillin resistant (MRSA)

31
Q

Furuncle on PE

A

-Hard, tender, red folliculocentric nodule, up to 1-2 cm
-Hair-bearing skin
-Enlarges and becomes painful and fluctuant (abscess) +/- pustule
-Zone of cellulitis may surround
Solitary or multiple lesions

32
Q

Define carbuncle

A
  • larger, more serious inflammatory lesion than furuncle with a deeper base
  • composed of several to multiple, adjacent, and coalescing furuncles
  • nape of the neck, the back, or thighs
33
Q

Carbundle on PE

A
  • Red, indurated nodule/plaque with multiple pustules, draining externally around multiple hair follicles
  • Develops a yellow–gray irregular crater at the center
  • **Extremely painful
  • Fever and malaise are often present
  • Results in scarring
34
Q

Define abscess

A
  • initially an erythematous nodule with formation of a pus-filled cavity
  • commonly occur in folliculocentric infections: folliculitis, furuncles, and carbuncles
  • can occur at sites of trauma, foreign bodies, burns, or insertion of intravenous catheters
35
Q

What organism should you think of when you think of abscess?

A

CA-MRSA should be suspected in all patients with abscess

36
Q

Etiology of Furuncle, Carbuncle, Abscess

A
  • Extensive furunculosis or carbuncle/abscess may be associated with leukocytosis
  • Diagnosis by clinical appearance
  • Obtain culture from pus
  • S. aureus is almost always the cause - CA-MRSA more than likely
37
Q

Surgical tx of Furuncle, Carbuncle, Abscess

A
  • Local application of moist heat (warm compress)
  • Large, painful, and fluctuant lesions need I&D in a timely manner
  • Simple incision with #11 scalpel blade: drainage with evacuation of the pus, probing the cavity to break up loculations
  • Wound can be packed with iodoform gauze to encourage further drainage
  • Draining lesions should be covered to prevent autoinoculation and diligent hand washing performed
38
Q

Pharm tx of Furuncle, Carbuncle, Abscess

A
  • *With surrounding cellulitis, associated fever or central facial involvement, need systemic antibiotic
  • MSSA: dicloxacillin, cephalexin, clindamycin, doxycycline, minocycline, and trimethoprim sulfamethoxazole
  • MRSA: clindamycin, doxycycline, minocycline, and trimethoprim sulfamethoxazole
  • MRSA treat with intranasal mupirocin (Bactroban) ointment twice a day for 5-7 days and antibacterial wash
39
Q

Define cellulitis

A
  • Acute spreading infection of the dermis and subcutaneous tissue
  • Common cause of inpatient hospital admissions
40
Q

Organisms that cause cellulitis

A
  • *S. aureus or Group A Strep
  • Pathogens gain entry via any break in the skin or mucosa
  • Tinea pedis and leg/foot ulcers common portals
41
Q

Cellulitis risk factors

A
  • chronic venous / arterial insufficiency
  • edema
  • surgery
  • intravenous drug use
  • body piercing
  • human and animal bites
  • diabetes
  • hepatic cirrhosis
  • immunosuppression
  • and neutropenia
42
Q

Clinical presentation of cellulitis

A
  • Acute onset of localized erythema, induration and tenderness
  • Erythema rapidly spreads and becomes intense
  • Borders may be ill-defined and surface crusts may develop
  • Overlying epidermis may have bulla formation or necrosis, resulting in extensive areas of epidermal sloughing and superficial erosion
  • Lymphangitis and regional lymphadenopathy may be associated
  • Usually presents in a unilateral distribution
43
Q

Systemic symptoms of cellulitis

A

fever, chills, and malaise are variable, and may precede localizing signs

44
Q

Dx of cellulitis

A
  • Dx generally made clinically
  • Epidermal swabs rarely helpful: organism found likely to be a colonizer or contaminant rather than a true pathogen
  • Uncommon for blood cultures skin bx for culture or skin aspirates to be +
  • Open wound: higher probability of + culture
45
Q

Define Erysipelas

A

Acute beta-hemolytic group A streptococcal infection of skin involving superficial dermal lymphatics

46
Q

S/sx of Erysipelas

A
  • Local redness, heat, swelling
  • Highly characteristic sharply demarcated raised indurated border
  • Surface findings are often described as peau d’orange (skin of an orange)
47
Q

Erysipelas vs. cellulitis

A

-More sharply defined margin and the erythema is classically bright red: compared to cellulitis

48
Q

Patient complaints with erysipelas

A

May be accompanied with malaise, chills, high fever, HA, vomiting and arthralgias

49
Q

Most common sites for erysipelas

A

Legs and face MC sites

50
Q

Predisposing factors for erysipelas

A
  • surgical wounds
  • fissures in nares, under the nose, between/under toes
  • abrasions
  • venous insufficiency
  • obesity
  • lymphedema
  • chronic leg ulcers

Dermatology 1 (19 decks)

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