5) Infectious Agents (Bacterial) Flashcards
Types of infections
- Erythrasma
- Pitted keratolysis
- Impetigo and ecthyma
- Erysipelas and cellulitis
- Wound infections
- Mycobacterial infections
- Leprosy
- Cutaneous TB
- Atypical mycobacteria
- Lyme borreliosis
Erythrasma, pitted keratolysis, and trichomycosis are all caused by
- Normal skin flora that overgrow secondary to environmental factors
Corynebacterium minutissium
- Gram +, non-spore-forming, aerobic
- Normal flora
- Causes exceedingly superficial infections
Corynebacterium minutissimum predisposing factors
- Warm humid environments or occlusion
- Increased risk in patients with DM, advanced age, or immunosuppression
Corynebacterium minutissimum symptoms
- Asymptomatic
- Low grade burn or itch
Corynebacterium minutissium physical examination
- 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
Corynebacterium minutissium DDx
- Dermatopyhtosis
- Candidiasis
- Seborrheic dermatitis
- Inverse psoriasis
Corynebacterium minutissium labs
- Wood’s lamp (coral red fluorescence)
- Gram stain (filamentous bacteria)
- Culture
Corynebacterium minutissium management
- 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
Kytococcus sedentarius (Corynebacterium species)
- Produces proteases that digest keratin
- Gram +
- Effects males > females (4:1) within age group of 21-30 most affected
Kytococcus sedentarius (Corynebacterium species) predisposing factors
- Hyperhidrosis
- Occlusive shoe gear
- Thickened skin of soles/palms
- Poor foot hygiene
- DM, obesity, and immunodeficiency
Kytococcus sedentarius (Corynebacterium species) symptoms
- Usually asymptomatic
- May lead to low grade burn or itch
- Very malodorous
Kytococcus sedentarius (corynebacterium species) physical examination
- Hyperhidrosis
- Maceration
- Slimy character to pedal skin
- Malodorous
- Crater-like pits, most numerous over heavily keratinized surfaces (less frequent on non-pressure areas)
Kytococcus sedentarius (Corynebacterium species) pitting characteristics
- Pits range from small and punctate to geographic
- Involved areas may appear white when hydrated
Kytococcus sedentarius (corynebacterium species) DDx
- Tinea pedis
- Plantar warts
- Dyshidrotic eczema
- Porokeratosis
Kytococcus sedentarius (corynebacterium species) labs
- Wood’s lamp (coral red) not a consistent finding
- Gram stain
- Culture
Kytococcus sedentarius (corynebacterium species) management
- Topical 2% erythromycin / 1% clindamycin
- Keep site dry and practice good foot hygiene (Topical
aluminum chloride hexahydrate for hyperhidrosis) - Oral erythromycin / tetracycline
Intertrigo
- Nonspecific term used to describe inflammation involving two closely opposed skin surfaces (infra-mammary, axillae, groin, interspaces)
Common intertrigo infections
- Grp A Strep, Grp B Strep
- C. minutissimum
- P. aeruginosa
- Candida
- Dermatophytes
Intertrigo can be mimicked by
- Inverse psoriasis
- Atopic dermatitis
Intertrigo management
- 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.
Primary impetigo
- Arises in minor breaks in the skin
Secondary impetigo arises in association with
- Alternate dermatoses (atopic dermatitis, stasis, psoriasis)
- Bullous disease (pemphigoid, pemphigus, porphyria)
- Ulcers
- Infections
Impetigo symptoms
- Pruritis
- Ecthyma (dermal involvement)
- Pain
Impetigo associated with S. aureus +/- beta-hemolytic streptococci
- Most common bacterial infection of the skin in childhood (2-5yrs)
- Superficial (epidermal), non-scarring pyoderma
- Dermal involvement (ulcerative type) –> Ecthyma
Impetigo predisposing factors
- Warm climate
- Poor hygiene
- Poverty
- Crowding
- Underlying scabies
- May also affect older children and adults
Three variants of impetigo
- Non-bullous
- Bullous
- Ecthyma
Non-bullous impetigo
- Papules, vesicles, and pustules
- Rapidly break down to form golden adherent crusts
- Often located on the face or extremities
Bullous impetigo
- Flaccid, fluid-filled bullae
- Rupture and leave a thin brown crust
- Often located on the trunk
Ecthyma
- “Punched-out” ulcers with overlying crusts and raised violaceous borders
Impetigo physical examination
- 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
Impetigo DDx
- ACD (allergic contact dermatitis)
- Herpes simplex
- Dermatophytosis
- Scabies
Impetigo labs
- Gram stain (+ cocci in chains or clusters)
- Culture
Impetigo management
- Prevention (good hygiene, benzoyl peroxide)
- Topical antibiotics (mupirocin) for limited skin involvement
- Oral antibiotics (as indicated) for ecthyma and/or greater skin involvement
Abscess
- Walled-off collection of purulence
Furuncle
- Acute, deep-seated tended nodule-forming abscess
- Stems from a staph folliculitis (infected follicle)
Carbuncle
- Deeper and farther reaching process
- Composed of several interconnecting abscesses involving several contiguous follicles (infected hair follicles)
Eryspielas and cellulitis
- Acute infections of the dermis and/or subcutis
- Often spreading out from a portal of entry
Erysipelas and cellulitis organisms
- Adults: S. aureus, Grp A Strep
- Children: H. influenzae type b, Grp A Strep, S. aureus
- Many others
Erysipelas and cellulitis occurrence
- Erysipelas peaks in children < 3 and the elderly
- Cellulitis is most common in middle aged and older adults
Erysipelas and cellulitis is predisposed by
- Skin Barrier Disruption
- Immunosuppression
- Chronic lymphedema
- DM
Erysipelas and cellulitis physical examination
- Areas of skin erythema, edema, and warmth
- Children: Head & neck (esp. cheeks)
- Adults: Lower leg, interdigital spaces
erysipelas and cellulitis organisms/patterns
- 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)
Erysipelas and cellulitis DDx
- Erysipelas: DVT, Stasis, ACD, bug bite, fixed drug eruption, erythema migrans (LYMES DZ), gout
- Necrotizing –DEEP SEETED: vasculitis, embolism with infarction, PVD
Erysipelas and cellulitis labs
- Gram Stain
- Histopathology
- Culture (identifies pathogen in only 20% of cases)
Erysipelas and cellulitis management
- 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
Wound infections
- MRSA is the most common organism isolated from hospital wounds
- Surgical site infection definition
Surgical site infection definition
- Occur within 30 days of surgery
- Involve skin and subcutis only
- Purulent d/c or + culture
- Inflammation
Leprosy
- Clinical form depends on immune response
- Tuberculoid
- Lepromatous
- Borderline (mixed)
Tuberculoid leprosy
- Local skin involvement
- Few organisms (abundant inflammation) seen
- BODY IS DOING GOOD JOB FIGHTING OFF INFXTN
Lepromatous leprosy
- Generalized skin involvement
- Many organisms (little inflammation) seen
- BODY DOING POOR JOB FIGHTING OFF BUG
M. leprae
- 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
M. leprae incidence
- Peaks at 10-20 years
- 600,000 new cases annually (200 in the US)
- Males > Females
- Darker skinned persons → higher incidence, but milder form
Mycobacterial infection (leprosy) risk factors
- Endemic region
- Genetic Predisposition
- Poverty
- Contact with infected armadillos
Mycobacterial infections (leprosy) incubation period
- 2-40 years
- VERY SLOW GROWING
Mycobacterial infections (leprosy) onset
- Insidious and painless
- Affects peripheral nerves leading to painful paresthesias and numbness (neuropathy)
- Nerve involvement may lead to muscle weakness
Mycobacterial infections (leprosy) physical examination
- Sensory neuropathy, neuropathic ulcers
- Destruction of nasal cartilage
- Cataracts due to anterior chamber colonization
- EYE IS COLDER THUS IT AFFECETS THE EYES
- Hypogonadism
- Amyloidosis
Mycobacterial infection (leprosy) DDx
- Sarcoidosis
- Lupus
- Syphilis
- Granuloma annulare
Mycobacterial infection (leprosy) labs
- Slit skin smears / nasal smears: smears stained with Ziehl-Neelson stain- poor sensitivity
- Culture (mouse foot pad)
- PCR
- Dermatopathology
Mycobacterial infections (leprosy) management
- Long-term multidrug treatment regimen
- TBD: Dapsone, rifampin
- Lepromatous: Dapsone, clofazimine, rifampin
Cutaneous tuberculosis (mycobacterial infections)
- Primary inoculation tuberculosis
- Tuberculosis verrucosa cutis
- Lupus vulgaris
- Scrofuloderma
Cutaneous tuberculosis (mycobacterial infections) primary innoculation tuberculosis
- 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
Tuberculosis verrucosa cutis (cutaneous TB, mycobacterial)
- 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
Scrofuloderma (cutaneous TB, mycobacterial)
- 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
Cutaneous TB/mycobacterial infections DDx
- Verrucosa: Verruca, Atypical mycobacteria, deep fungal infections, SCC, LP
- Lupus vulgaris: Sarcoidosis, lymphoma, Lupus erythematosis, leprosy
- Scrofuloderma: deep fungal infections, nocardia, actinomyces, hidradenitis suppurativa
Cutaneous TB/mycobacterial infections labs
- 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
Cutaneous TB/mycobacterial infections management
- 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
Atypical mycobacteria
- M. marinum
- M. ulcerans
- M. fortuitum complex
Mycobacterium marinum
- Tropical fish tanks
- Chlorine sensitive
- 2nd to 4th decades
- Males > females
- Largely asymptomatic
Mycobacterium marinum physical exam
- Papule at inoculation site(s) → forms red-brown nodule or plaque → verrucous surface
- May become ulcerated
- Regional lymphadenopathy
Mycobacterium marinum DDx
- Deep fungal infection
- Nocardia
- Actinomyces
- Neoplasms
Mycobacterium marinum labs
- Skin test: PPD-S may be positive
- Skin Biopsy: suggestive, organism identified in half of cases
- Culture: 32˚C for 2 - 4 weeks
Mycobacterium marinum management
- Antibiotics
- Surgical debridement
Mycobacterium ulcerans
- Children
- Females > males
- Transmission via inoculation from contaminated plants (swamps)
- Toxin mycolactone causes tissue damage
Mycobacterium ulcerans physical examination
- Inoculation → enlarging painless ulcer
- Usually involves the
legs
Mycobacterium ulcerans DDx
- Infectious
- BCC
- SCC
- Pyoderma gangrenosum
Mycobacterium ulcerans labs
- Culture
- PCR
- Dermatopathology (organisms
easily found in most cases)
Mycobacterium ulcerans management
- Heat
- Surgery
- Antimycobacterial therapy
Mycobacterium fotruitum complex
- M. fortuitum: world-wide
- M. chelonae: Europe
- M. abscessus: US and Africa
- Organisms found in soil, dust and water
Mycobacterium fortuitum complex transmission
- Trauma
- Surgical procedures
- Whirlpools: famous for hot water path/nail salons etc.
Mycobacterium fotruitum complex physical examination
- Dark red nodule +/- abscess at incision site or site of alternate trauma
Mycobacterium fortuitum complex DDx
- Purulent bacterial infections
- FB reactions
Mycobaterium fortuitum complex management
- Antimycobacterials
- Surgery
Lyme borreliosis
- 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
Lyme borreliosis transmission
- Ticks during hiking, camping, etc.
- Eastern US: between May and early fall
- Pacific Northwest: Jan – May
Lyme borreliosis stage 1
- 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
Lyme borreliosis stage 2
- Disseminated infection (secondary lesions)
- Arise in 17-50% of cases with dissemination
- Resembles erythema migrans, but smaller
Lyme borreliosis stage 3
- Persistent infection (acrodermatitis chronica atrophicans)
- Early- local or diffuse erythema
- Late- cigarette paper skin
- Sclerotic or fibrotic plaques and bands (knees and elbows)
Lyme borreliosis neurologic involvement
- 10-20% of untreated Lyme Disease
- 1-6 weeks after tick bite
- Meningitis, cranial neuritis, cephalitic signs (memory, sleep abnormalities)
Lyme borreliosis labs
- Serology: Initial test = ELISA, confirm with Western blot
- Culture: organism may sometimes be isolated
- PCR: Preferred confirmatory test
- Dermatopathology: organisms in 40% of EM
Lyme borreliosis management
- Prophylaxis: avoid habitat, repellent, amoxicillin or doxycycline
- Immunization: for those at high risk
- Antibiotics
