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Dermatology > 5) Infectious Agents (Bacterial) > Flashcards

5) Infectious Agents (Bacterial) Flashcards

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1
Q

Types of infections

A
  • Erythrasma
  • Pitted keratolysis
  • Impetigo and ecthyma
  • Erysipelas and cellulitis
  • Wound infections
  • Mycobacterial infections
  • Leprosy
  • Cutaneous TB
  • Atypical mycobacteria
  • Lyme borreliosis
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2
Q

Erythrasma, pitted keratolysis, and trichomycosis are all caused by

A
  • Normal skin flora that overgrow secondary to environmental factors
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3
Q

Corynebacterium minutissium

A
  • Gram +, non-spore-forming, aerobic
  • Normal flora
  • Causes exceedingly superficial infections
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4
Q

Corynebacterium minutissimum predisposing factors

A
  • Warm humid environments or occlusion

- Increased risk in patients with DM, advanced age, or immunosuppression

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5
Q

Corynebacterium minutissimum symptoms

A
  • Asymptomatic

- Low grade burn or itch

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6
Q

Corynebacterium minutissium physical examination

A
  • Well delineated macule or patch which may be erythematous or brown
  • Scale when dry, macerated when damp
  • May fissure
  • If pruritic, may be eroded or lichenified
  • May co-infect with dermatophyte or Candida
  • Interdigital > groin > axillae > other intertriginous areas
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7
Q

Corynebacterium minutissium DDx

A
  • Dermatopyhtosis
  • Candidiasis
  • Seborrheic dermatitis
  • Inverse psoriasis
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8
Q

Corynebacterium minutissium labs

A
  • Wood’s lamp (coral red fluorescence)
  • Gram stain (filamentous bacteria)
  • Culture
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9
Q

Corynebacterium minutissium management

A
  • Topical erythromycin / clindamycin 0.2%
  • Prevention by keep site dry (benzoyl peroxide, other)
  • Oral erythromycin 1g per day (divided) for 14 days or a single dose clarithromycin 1g
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10
Q

Kytococcus sedentarius (Corynebacterium species)

A
  • Produces proteases that digest keratin
  • Gram +
  • Effects males > females (4:1) within age group of 21-30 most affected
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11
Q

Kytococcus sedentarius (Corynebacterium species) predisposing factors

A
  • Hyperhidrosis
  • Occlusive shoe gear
  • Thickened skin of soles/palms
  • Poor foot hygiene
  • DM, obesity, and immunodeficiency
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12
Q

Kytococcus sedentarius (Corynebacterium species) symptoms

A
  • Usually asymptomatic
  • May lead to low grade burn or itch
  • Very malodorous
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13
Q

Kytococcus sedentarius (corynebacterium species) physical examination

A
  • Hyperhidrosis
  • Maceration
  • Slimy character to pedal skin
  • Malodorous
  • Crater-like pits, most numerous over heavily keratinized surfaces (less frequent on non-pressure areas)
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14
Q

Kytococcus sedentarius (Corynebacterium species) pitting characteristics

A
  • Pits range from small and punctate to geographic

- Involved areas may appear white when hydrated

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15
Q

Kytococcus sedentarius (corynebacterium species) DDx

A
  • Tinea pedis
  • Plantar warts
  • Dyshidrotic eczema
  • Porokeratosis
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16
Q

Kytococcus sedentarius (corynebacterium species) labs

A
  • Wood’s lamp (coral red) not a consistent finding
  • Gram stain
  • Culture
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17
Q

Kytococcus sedentarius (corynebacterium species) management

A
  • Topical 2% erythromycin / 1% clindamycin
  • Keep site dry and practice good foot hygiene (Topical
    aluminum chloride hexahydrate for hyperhidrosis)
  • Oral erythromycin / tetracycline
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18
Q

Intertrigo

A
  • Nonspecific term used to describe inflammation involving two closely opposed skin surfaces (infra-mammary, axillae, groin, interspaces)
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19
Q

Common intertrigo infections

A
  • Grp A Strep, Grp B Strep
  • C. minutissimum
  • P. aeruginosa
  • Candida
  • Dermatophytes
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20
Q

Intertrigo can be mimicked by

A
  • Inverse psoriasis

- Atopic dermatitis

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21
Q

Intertrigo management

A
  • Castellani’s paint
  • Anti-fungal and anti-bacterial powders (you have to do a biopsy to know what your dealing with)
  • Ventilation
  • Treat the predisposing conditions as obesity, incontinence, DM, etc.
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22
Q

Primary impetigo

A
  • Arises in minor breaks in the skin
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23
Q

Secondary impetigo arises in association with

A
  • Alternate dermatoses (atopic dermatitis, stasis, psoriasis)
  • Bullous disease (pemphigoid, pemphigus, porphyria)
  • Ulcers
  • Infections
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24
Q

Impetigo symptoms

A
  • Pruritis
  • Ecthyma (dermal involvement)
  • Pain
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25
Q

Impetigo associated with S. aureus +/- beta-hemolytic streptococci

A
  • Most common bacterial infection of the skin in childhood (2-5yrs)
  • Superficial (epidermal), non-scarring pyoderma
  • Dermal involvement (ulcerative type) –> Ecthyma
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26
Q

Impetigo predisposing factors

A
  • Warm climate
  • Poor hygiene
  • Poverty
  • Crowding
  • Underlying scabies
  • May also affect older children and adults
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27
Q

Three variants of impetigo

A
  • Non-bullous
  • Bullous
  • Ecthyma
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28
Q

Non-bullous impetigo

A
  • Papules, vesicles, and pustules
  • Rapidly break down to form golden adherent crusts
  • Often located on the face or extremities
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29
Q

Bullous impetigo

A
  • Flaccid, fluid-filled bullae
  • Rupture and leave a thin brown crust
  • Often located on the trunk
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30
Q

Ecthyma

A
  • “Punched-out” ulcers with overlying crusts and raised violaceous borders
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31
Q

Impetigo physical examination

A
  • Superficial small vesicles which rupture leading to
    golden crust formation
  • Satellite lesions by auto-inoculation
  • Bullous lesions rupture to reveal shallow erosion, more common intertriginous
  • Ecthyma: Ulceration, painful, distal extremities
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32
Q

Impetigo DDx

A
  • ACD (allergic contact dermatitis)
  • Herpes simplex
  • Dermatophytosis
  • Scabies
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33
Q

Impetigo labs

A
  • Gram stain (+ cocci in chains or clusters)

- Culture

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34
Q

Impetigo management

A
  • Prevention (good hygiene, benzoyl peroxide)
  • Topical antibiotics (mupirocin) for limited skin involvement
  • Oral antibiotics (as indicated) for ecthyma and/or greater skin involvement
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35
Q

Abscess

A
  • Walled-off collection of purulence
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36
Q

Furuncle

A
  • Acute, deep-seated tended nodule-forming abscess

- Stems from a staph folliculitis (infected follicle)

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37
Q

Carbuncle

A
  • Deeper and farther reaching process

- Composed of several interconnecting abscesses involving several contiguous follicles (infected hair follicles)

38
Q

Eryspielas and cellulitis

A
  • Acute infections of the dermis and/or subcutis

- Often spreading out from a portal of entry

39
Q

Erysipelas and cellulitis organisms

A
  • Adults: S. aureus, Grp A Strep
  • Children: H. influenzae type b, Grp A Strep, S. aureus
  • Many others
40
Q

Erysipelas and cellulitis occurrence

A
  • Erysipelas peaks in children < 3 and the elderly

- Cellulitis is most common in middle aged and older adults

41
Q

Erysipelas and cellulitis is predisposed by

A
  • Skin Barrier Disruption
  • Immunosuppression
  • Chronic lymphedema
  • DM
42
Q

Erysipelas and cellulitis physical examination

A
  • Areas of skin erythema, edema, and warmth
  • Children: Head & neck (esp. cheeks)
  • Adults: Lower leg, interdigital spaces
43
Q

erysipelas and cellulitis organisms/patterns

A
  • S. aureus: Percutaneous injury (IV) (most common route)
  • Group A Strep: 37% with necrotizing fasciitis, 25% have streptococcal TSS (mortality 21%)
  • P. aeruginosa: Ecthyma gangrenosum- erythematous macule → bluish plaque (infarct) → Bulla formation → ulceration
  • H. influenzae: children < 2 years of age, head and neck involvement (cheeks)
44
Q

Erysipelas and cellulitis DDx

A
  • Erysipelas: DVT, Stasis, ACD, bug bite, fixed drug eruption, erythema migrans (LYMES DZ), gout
  • Necrotizing –DEEP SEETED: vasculitis, embolism with infarction, PVD
45
Q

Erysipelas and cellulitis labs

A
  • Gram Stain
  • Histopathology
  • Culture (identifies pathogen in only 20% of cases)
46
Q

Erysipelas and cellulitis management

A
  • Prophylaxis: antibiotics, local care
  • Dressings: sterile saline
  • Surgical intervention: drain abscesses, debride necrotic tissue
  • Oral antibiotics: healthy person with early infection
  • IV antibiotics: rapidly spreading, immuno-suppression, fever
47
Q

Wound infections

A
  • MRSA is the most common organism isolated from hospital wounds
  • Surgical site infection definition
48
Q

Surgical site infection definition

A
  • Occur within 30 days of surgery
  • Involve skin and subcutis only
  • Purulent d/c or + culture
  • Inflammation
49
Q

Leprosy

A
  • Clinical form depends on immune response
  • Tuberculoid
  • Lepromatous
  • Borderline (mixed)
50
Q

Tuberculoid leprosy

A
  • Local skin involvement
  • Few organisms (abundant inflammation) seen
  • BODY IS DOING GOOD JOB FIGHTING OFF INFXTN
51
Q

Lepromatous leprosy

A
  • Generalized skin involvement
  • Many organisms (little inflammation) seen
  • BODY DOING POOR JOB FIGHTING OFF BUG
52
Q

M. leprae

A
  • Acid-fast obligate intra-cellular bacillus (LIVES INSIDE OTHER CELLS)
  • Slow-growing and fastidious
  • Prefers cooler temp (eye, lung, extremities) = THIS IS WHY YOU SEE IT IN COLDER AREAS
53
Q

M. leprae incidence

A
  • Peaks at 10-20 years
  • 600,000 new cases annually (200 in the US)
  • Males > Females
  • Darker skinned persons → higher incidence, but milder form
54
Q

Mycobacterial infection (leprosy) risk factors

A
  • Endemic region
  • Genetic Predisposition
  • Poverty
  • Contact with infected armadillos
55
Q

Mycobacterial infections (leprosy) incubation period

A
  • 2-40 years

- VERY SLOW GROWING

56
Q

Mycobacterial infections (leprosy) onset

A
  • Insidious and painless
  • Affects peripheral nerves leading to painful paresthesias and numbness (neuropathy)
  • Nerve involvement may lead to muscle weakness
57
Q

Mycobacterial infections (leprosy) physical examination

A
  • Sensory neuropathy, neuropathic ulcers
  • Destruction of nasal cartilage
  • Cataracts due to anterior chamber colonization
  • EYE IS COLDER THUS IT AFFECETS THE EYES
  • Hypogonadism
  • Amyloidosis
58
Q

Mycobacterial infection (leprosy) DDx

A
  • Sarcoidosis
  • Lupus
  • Syphilis
  • Granuloma annulare
59
Q

Mycobacterial infection (leprosy) labs

A
  • Slit skin smears / nasal smears: smears stained with Ziehl-Neelson stain- poor sensitivity
  • Culture (mouse foot pad)
  • PCR
  • Dermatopathology
60
Q

Mycobacterial infections (leprosy) management

A
  • Long-term multidrug treatment regimen
  • TBD: Dapsone, rifampin
  • Lepromatous: Dapsone, clofazimine, rifampin
61
Q

Cutaneous tuberculosis (mycobacterial infections)

A
  • Primary inoculation tuberculosis
  • Tuberculosis verrucosa cutis
  • Lupus vulgaris
  • Scrofuloderma
62
Q

Cutaneous tuberculosis (mycobacterial infections) primary innoculation tuberculosis

A
  • Site of percutaneous trauma
  • 2-4 weeks development of painless ulcer, i.e. “tuberculous chancre”- TB CHANCRE IS PAINLESS!!!
  • Small abscesses
  • Usually at sites of minor trauma
  • Oral lesions may arise after consuming bovine bacilli in non-pasteurized milk
63
Q

Tuberculosis verrucosa cutis (cutaneous TB, mycobacterial)

A
  • Papule on violaceous base
  • Evolves to verrucous
    hyperkeratotic plaque
  • Single or multiple
  • Adults: upper extremity – will look just like verrucae vulgaris on hands
  • Children: lower extremities
64
Q

Scrofuloderma (cutaneous TB, mycobacterial)

A
  • Commonly involves neck, axillae, and groin lymph nodes
    with the cervical lymph nodes being most common source
  • Firm subcutaneous nodule which are initially freely moveable, but increasingly anchored over time
  • Ulcerations with discharge and sinus formation
65
Q

Cutaneous TB/mycobacterial infections DDx

A
  • Verrucosa: Verruca, Atypical mycobacteria, deep fungal infections, SCC, LP
  • Lupus vulgaris: Sarcoidosis, lymphoma, Lupus erythematosis, leprosy
  • Scrofuloderma: deep fungal infections, nocardia, actinomyces, hidradenitis suppurativa
66
Q

Cutaneous TB/mycobacterial infections labs

A
  • Skin testing- positive in LV and TVC (+/- in other variants)
  • Culture which yields organisms
  • PCR has a high sensitivity
  • Dermatopathology- organisms may be rare or absent in LV and TVC
67
Q

Cutaneous TB/mycobacterial infections management

A
  • Primary inoculation TB and TB verrucosa cutis are the only primary cutaneous forms
  • Other variants are systemic with secondary skin infection
  • Multi-drug therapy for all forms of cutaneous TB except tuberculosis verrucosa cutis which can be treated by simple excision
68
Q

Atypical mycobacteria

A
  • M. marinum
  • M. ulcerans
  • M. fortuitum complex
69
Q

Mycobacterium marinum

A
  • Tropical fish tanks
  • Chlorine sensitive
  • 2nd to 4th decades
  • Males > females
  • Largely asymptomatic
70
Q

Mycobacterium marinum physical exam

A
  • Papule at inoculation site(s) → forms red-brown nodule or plaque → verrucous surface
  • May become ulcerated
  • Regional lymphadenopathy
71
Q

Mycobacterium marinum DDx

A
  • Deep fungal infection
  • Nocardia
  • Actinomyces
  • Neoplasms
72
Q

Mycobacterium marinum labs

A
  • Skin test: PPD-S may be positive
  • Skin Biopsy: suggestive, organism identified in half of cases
  • Culture: 32˚C for 2 - 4 weeks
73
Q

Mycobacterium marinum management

A
  • Antibiotics

- Surgical debridement

74
Q

Mycobacterium ulcerans

A
  • Children
  • Females > males
  • Transmission via inoculation from contaminated plants (swamps)
  • Toxin mycolactone causes tissue damage
75
Q

Mycobacterium ulcerans physical examination

A
  • Inoculation → enlarging painless ulcer
  • Usually involves the
    legs
76
Q

Mycobacterium ulcerans DDx

A
  • Infectious
  • BCC
  • SCC
  • Pyoderma gangrenosum
77
Q

Mycobacterium ulcerans labs

A
  • Culture
  • PCR
  • Dermatopathology (organisms
    easily found in most cases)
78
Q

Mycobacterium ulcerans management

A
  • Heat
  • Surgery
  • Antimycobacterial therapy
79
Q

Mycobacterium fotruitum complex

A
  • M. fortuitum: world-wide
  • M. chelonae: Europe
  • M. abscessus: US and Africa
  • Organisms found in soil, dust and water
80
Q

Mycobacterium fortuitum complex transmission

A
  • Trauma
  • Surgical procedures
  • Whirlpools: famous for hot water path/nail salons etc.
81
Q

Mycobacterium fotruitum complex physical examination

A
  • Dark red nodule +/- abscess at incision site or site of alternate trauma
82
Q

Mycobacterium fortuitum complex DDx

A
  • Purulent bacterial infections

- FB reactions

83
Q

Mycobaterium fortuitum complex management

A
  • Antimycobacterials

- Surgery

84
Q

Lyme borreliosis

A
  • US: Borrelia burgdorferi
  • Europe and Asia: Borrelia garinii and Borrelia afzelii
  • Vector: Ixodes dammini
  • Animal hosts: white footed mouse (larvae), white tailed deer (adult)
  • Most common vector borne infection in US
85
Q

Lyme borreliosis transmission

A
  • Ticks during hiking, camping, etc.
  • Eastern US: between May and early fall
  • Pacific Northwest: Jan – May
86
Q

Lyme borreliosis stage 1

A 
- Localized infection (Erythema
Migrans, Borrelia lymphocytoma, other)
- Arise at the site of the tick feed
- EM enlarges with central clearing
- Lymphocytoma more common in Europe
87
Q

Lyme borreliosis stage 2

A
  • Disseminated infection (secondary lesions)
  • Arise in 17-50% of cases with dissemination
  • Resembles erythema migrans, but smaller
88
Q

Lyme borreliosis stage 3

A
  • Persistent infection (acrodermatitis chronica atrophicans)
  • Early- local or diffuse erythema
  • Late- cigarette paper skin
  • Sclerotic or fibrotic plaques and bands (knees and elbows)
89
Q

Lyme borreliosis neurologic involvement

A
  • 10-20% of untreated Lyme Disease
  • 1-6 weeks after tick bite
  • Meningitis, cranial neuritis, cephalitic signs (memory, sleep abnormalities)
90
Q

Lyme borreliosis labs

A
  • Serology: Initial test = ELISA, confirm with Western blot
  • Culture: organism may sometimes be isolated
  • PCR: Preferred confirmatory test
  • Dermatopathology: organisms in 40% of EM
91
Q

Lyme borreliosis management

A
  • Prophylaxis: avoid habitat, repellent, amoxicillin or doxycycline
  • Immunization: for those at high risk
  • Antibiotics

Dermatology (5 decks)

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