infectious dermatology Flashcards
impetigo - what pathogen is responsible for MSSA and MRSA
S aureus
what pathogen causes bullous impetigo
Epidermolytic toxin A – producing S. aureus causes scalded skin syndrome
impetigo: Beta – hemolytic strep is what group?
group A
impetigo is MC in who
children but any age
impetigo MC occurs where?
- Minor breaks in the skin
- Around the nose
- Atopic dermatitis
- Traumatic wounds
Bullous stains of S. aureus = exfoliative toxin A leads to?
Bullous Impetigo
leads to loss of cell adhesion in the superficial epidermis
Bullous stains of S. aureus is MC in what age?
Bullous Impetigo
newborn and older infants
Often asx
Can be painful and tender
Erosions with crusts
1 – 3 cm lesions
Central healing often after several weeks
Regional lymphadenopathy
Impetigo Non-bullous
arrangement of Impetigo Non-bullous
Scattered, discrete lesions
w/o tx confluent
Satellite lesions occur from autoinoculation
impetigo vesicles can progress quickly to ?
bullae
- No erythema noted
- filled with serous fluid
- Yellow –> dark brown
- (-) Nikolsky sign
? days = collapse and leave erosions with crusts
Impetigo Bullous
1-2
nikolsky sign?
a skin finding in which the top layers of the skin slip away from the lower layers when rubbed
dx impetigo
Gram stain and culture often necessary for bullous type
impetigo tx
- Warm water soaks x 15-20 min BID
- mupirocin x 5 d.
- For widespread infection = 7 d ABX
- Cephalexin
- Erythromycin - MRSA = Doxy
- Critically ill patients with MRSA/MRSA = vanc/linezolid
- Bullous or severe = PO ABX
pt ed for impetigo
- Good Hygiene
- Nails, proper soap, frequent washing - Underlying condition tx
- Mupirocin in other areas where skin barrier has been broken
- Wounds covered
- Avoid contact with others (>24hrs post ABX initiation)
prevention impetigo
- BPO wash
- Check family members for signs
- Ethanol or isopropyl gel for hands
- Infection of the hair follicle with +/- pus in the ostium of the follicle
- Non tender /slightly tender
- Pruritic
Folliculitis
causes of Folliculitis (pathogens)
- Bacteria (S.aureus)
- Fungi
- Mites
- Virus
prediposing factors for folliculitis
- Shaving hair bearing areas
- Occlusion of hair bearing areas
- Hot tub usage
- Topical CS
- Systemic ABX (G- can proliferate)
- Diabetes
- Immunosuppression
Folliculitis - Can progress and become ?
an abscess or furuncle formation
What causes folliculitis to progress it into an abscess or furuncle formation?
pathogens
- S. aureus
- Pseudomonas (hot tub) - MC trunk
- Viral (herpetic and molluscum)
- Fungal (candida, malassezia)
- Other: Syphilitic
G- to acne pt who worsens on systemic ABX w/ small follicular pustules = ?
gram neg folliculitis
dx folliculitis
clinical
gram stain
C&S
KOH (fungal)
mild tc folliculitis
- Warm compresses
- Wash with BPO or antibacterial soap (dial)
- ABX if spontaneous resolution does not occur within 2-3 weeks or if symptoms worsen
tx moderate folliculitis
- Clindamycin BID x 10 days
- Mupirocin TID x 10 days
tx severe folliculitis
MSSA/MRSA
- Oral – MSSA - Cephalexin (Keflex)
- Oral – MRSA
- Doxycycline 100mg BID x 10 days
- Bactrim
prevention folliculitis
BPO body wash
Chlorhexidine body wash
- Collection of pus accumulated in a tissue = inflammatory response to an infectious process of foreign body
- Acute or chronic localized inflammation
- Arises in any organ or tissue
Abscess
Arises in any organ or tissue - Skin & dermis, subcutaneous fat, muscle, or a variety
- Tender
- Red
- Hot
- Indurated nodule
- +/- fever + constitutional sx
- Days / weeks = pus formation (within a central space)
Abscess
dx abscess
Gram Stain and C&S of exudate
Typically MSSA or MRSA
tx abscess
- I&D
- ABX Therapy.
indications for abx for abscess
- Single abscess ≥2 cm
- Multiple lesions
- Extensive surrounding cellulitis
- Immunosuppression or other comorbidities
- S/S toxicity ( fever >100.5°F, hypotension, or sustained tachycardia)
- Inadequate clinical response to I&D alone
- Indwelling medical device (prosthetic joint, vascular graft, or pacemaker)
- High risk for transmission of S. aureus to others (athletes, group home)
oral vs IV Abx for abscess
- Toxic? - Fever, Hypotension, Tachycardia
- Rapid progression after 48hr of PO ABX?
- Inability to tolerate orals?
- Close to indwelling device? - Prosthetics, graft, catheter
abscess - For large lesions consider ?
surgery with general surgeon or plastics
Difficult areas
* Palms
* Soles
* Nasolabial areas
* Genitalia
prevention abscess
- Antibacterial soap or BPO wash
- Avoid heat and friction
- Educate patients to Avoid squeezing (PATIENTS LOVE TO DO THIS)
- Acute, deep seated, red, hot, tender nodule or abscess
- Abscess = boil
- 1-2 cm
- Fluctuant - Nodule with cavitation after drainage
- Any hair bearing region
- from a staphylococcal folliculitis
Furuncle
furuncle management
- Warm compresses 10 min daily; Erythema = ABX probably necessary
- Bactrim, Clindamycin, Doxycycline
- Deeper infection composed of interconnecting abscesses usually arising in several contiguous hair follicles
- Patient is typically ill appearing
- Fever + along with constitutional sx
- Painful/tender
Carbuncle
MC locations for Carbuncle
nape of neck, back, and thighs
dx carbuncle
Clinical gram stain is helpful with C&S
tx for carbuncle
- uncomplicated - Bactrim, Clindamycin, Doxycycline
- COMPLICATED = ADMISSION FOR IV ABX
admission for Carbuncle if? tx?
- Toxic appearing
- Rapid progression
- No improvement after 24-48 hours of PO ABX
Vancomycin 1-2 g IV daily DOC
Rapid progression of infection with extensive necrosis of soft tissues and overlying skin
AKA: Flesh eating disease
Necrotizing Fasciitis
etiology Necrotizing Fasciitis
polymicrobial
- Beta-hemolytic GAS
- Pseudomonas aeruginosa
- Clostridium
pathophys of Necrotizing Fasciitis
Bacteria release enzymes/gases that degrade fascia resulting in rapid proliferation, local thrombosis, ischemia and necrosis
Necrotizing Fasciitis may be began as?
May begin deep at site of nonpenetrating minor trauma
- bruise, muscle, or strain
- Minor trauma
- Laceration
- Needle puncture
- Surgical incision
Necrotizing Fasciitis is MC in what age?
Middle age (mid 30 - mid 40’s)
RF Necrotizing Fasciitis
- DM
- ETOH abuse
- liver dz
- CKD
- malnutrition
Necrotizing Fasciitis - If skin necrosis is not obvious suspect if there are signs of sepsis and/or some of the following local symptoms:
- Severe pain
- Indurated swelling
- Bullae
- Cyanosis
- Skin pallor
- Skin hypesthesia
- Crepitation
- Muscle weakness
- Foul smelling exudates
Necrotizing Fasciitis - 4 signs to identify
- Local redness
- Edema
- Warmth
- Pain
- Appears 36 – 72 hours after onset
- Involves soft tissue becomes blue in color
- Vesicles and bullae appear - spread along fascial plane
Necrotizing Fasciitis progression
Extensive cutaneous soft tissue necrosis develops
- Black eschar with surrounding irregular border of erythema
- Fever and other constitutional symptoms
ddx Necrotizing Fasciitis
- Pyoderma gangrenosum
- Calciphylaxis
- Purpura fulminans
- Warfarin necrosis
- Pressure ulcer
- Brown recluse spider bite
Key clinical red flags of Necrotizing Fasciitis:
- Severe, constant pain out of proportion to physical exam, or anesthesia
- Erythema evolving into a dusky gray color
- Malodorous, watery “dirty dishwater” discharge
- Gas (crepitus, or crackling sounds) in the soft tissues
- Edema extending beyond areas of erythema
- Rapid progression despite antibiotic therapy
tx Necrotizing Fasciitis
- Surgical debridement
- CBC, CMP, CK, ABG, UA, serum/deep tissue culture
- CT, MRI, Plain film - GAS? - broad spectrum ABX
- Carbepenem
- Ampicillin/sulbactam
- Clindamycin
- MRSA - Vancomycin
all dependent on gram stain / C&S
Acute superficial infection (dermis and dermal lymphatic vessels)
Erysipelas
MCC Erysipelas
group A 𝛃-hemolytic streptococcus
Erysipelas is MC in what age
young children and older adults
s/s erysipelas
- Prodrome - fever, chills, anorexia, malaise
- General - +/- signs of sepsis
- Lesion
- painful/tender/hot
- bright red, raised, edematous, indurated plaque
- sharp borders
Acute infection of the dermis and subcutaneous tissue
Cellulitis
etiology Cellulitis
- S. aureus (MC) and Group A β-hemolytic streptococcus
- Cat/Dog trauma: Pasteurella multocida
- Freshwater wound: Aeromonas
Epidemiology Cellulitis
MC middle age adults
cellulitis - A focused history should determine ?
- immune status
- comorbid conditions
- possible sites and causes of skin barrier disruption
- prior h/o cellulitis, and methicillin-resistant S. aureus (MRSA) risk factors
s/s cellulitis
- (Similar to erysipelas)
- Prodrome - fever, chills, anorexia, malaise
- General - +/- signs of sepsis
- Lesion
- painful/tender/hot
- bright red, edematous, (+/- induration)
- indistinct borders (not raised)
RF cellulitis
- Minor skin trauma
- Body piercing
- Intravenous drug use
- Tinea pedis infection
- Animal bites
- Peripheral vascular disease
- Immune suppression (chronic systemic steroid use, neutropenia, immunosuppressive medications, alcohol use disorder)
- Lymphatic damage (lymph node dissection, radiation therapy, vein harvest for coronary artery bypass surgery, and damage that occurs following multiple prior episodes of cellulitis)
RF Erysipelas & Cellulitis
- Compromised skin integrity - atopic dermatitis, insect bite, surgery, trauma, IV drug use
- Compromised immune system - AIDS, DM, ESRD, CA, immunosuppressive therapy, drug/ETOH abuse
ddx Erysipelas & Cellulitis
- DVT
- stasis dermatitis
- contact dermatitis,
- urticaria
- insect bite
- fixed drug eruption
- erythema nodosum
- acute gout
- erythema migrans (Lyme)
- pre-vesicular herpes zoster
dx w/u for Erysipelas & Cellulitis
- **Clinical dx **
- Labs only if systemic symptoms are present
- CBC, CMP, ESR, blood cx - Imaging - US or MRI if needed
indications for imaging for Erysipelas & Cellulitis
ruling out abscess, necrotizing fasciitis, pyomyositis, and gas forming anaerobic bacterial infection
complications from Erysipelas & Cellulitis
Abscess formation, bacteremia, endocarditis, osteomyelitis, metastatic infection, sepsis, toxic shock syndrome
indications for Erysipelas & Cellulitis for IV abx
- Systemic presentation: Fever > 100.5, hypotension, sustained tachycardia
- Rapidly spreading lesion
- Progression of clinical features after 48 h of oral abx
- Unable to tolerate oral therapy
- Comorbidities: immunosuppression, neutropenia, asplenia, cirrhosis, heart/renal failure
can be switched to PO once systemic s/s resolve
IV tx for Erysipelas & Cellulitis (MRSA & MSSA)
- MRSA coverage
- vancomycin (1st line)
- daptomycin (2nd line) - MSSA coverage
- cefazolin
- clindamycin
- nafcillin
oral therapy for Erysipelas & Cellulitis
MRSA& MSSA
- MRSA coverage
- clindamycin (first line)
- amoxicillin + TMP-SMX/doxycycline - MSSA coverage
- cephalexin
- nafcillin
- clindamycin
Special considerations in treatment for Erysipelas & Cellulitis
- Dog/cat bite: Augmentin - Pasteurella multocida
- Human bite: Augmentin - Eikenella, Group A Streptococcus; Broad spectrum ABX
- Exposure to fresh water: cipro - Aeromonas
- Exposure to salt water: doxy - Vibrio vulnificus
Acute inflammatory process involving the subcutaneous lymphatic channels
Lymphangitis
causes of acute & chronic Lymphangitis
- GAS, S. aureus, Herpes simplex virus
- Chronic - Mycobacterium marinum
portals of Lymphangitis
- Break in skin
- Wound
- Paronychia
- Primary herpes simplex
- Pain +/- erythema proximal to break in skin
- Red linear streaks and palpable lymphatic cord
Lymphangitis
ddx Lymphangitis
- Phyto-allergic contact dermatitis
- Superficial thrombophlebitis
- Mycobacterium marinum
- N. brasiliensis
- S. schenckii
dx Lymphangitis
-
Clinical dx
- Resolves with correct diagnosis and treatment
- cx if open and actively weeping - Labs only if systemic sx
- CBC, CMP, blood cultures
tx Lymphangitis
- Oral ABX dependent on sensitivity
- Dicloxacillin or 1st generation cephalosporin
- MRSA Clinda or Bactrim - F/u 24-48 hours
- ABX indications: toxic appearing or no improvement after 24-48 hours
Superficial fungal infection of the skin
Cutaneous Candidiasis
MC pathogen causing Cutaneous Candidiasis
Candida albicans
MC ages for Cutaneous Candidiasis
neonates and adults >65 years old
MC areas involved for Cutaneous Candidiasis
Genitocrural, gluteal, interdigital, inframammary, axilla, under pannus
Cutaneous Candidiasis RF
- Obesity
- DM
- local occlusion/moisture
- steroid/abx use
- hyperhidrosis
- incontinence
- Pruritic
- Tender/painful
- Macerated
- Erythematous
- Satellite lesions typically present; beefy red
Cutaneous Candidiasis
dx Cutaneous Candidiasis
KOH prep
ddx Cutaneous Candidiasis
- Tinea
- Psoriasis
- Dermatitis
- AD
- Secondary syphilis
tx Mild to moderate
Cutaneous Candidiasis
Topical antifungals 2-3 wks - Continue x 2 weeks after clearance
- Ketoconazole
- Econazole
- Clotrimazole
- Miconazole
tx for severe cutaneous candidiasis
Oral antifungals
Fluconazole (Diflucan) 100mg PO daily x 2-3 weeks
prevention of Cutaneous Candidiasis
Keep areas dry
- Powders (Zeasorb AF)
- Hair dryer
- Avoid occlusive clothing
- Inflammation of the glans penis, can be triggered by numerous factors.
- Affects uncircumcised men with poor hygiene.
Balanitis
common infectious triggers for Balanitis
candida, Trichomonas vaginalis, gonorrhoeae, streptococcus
hx components for balanitis
DM, culture, KOH, Tzank smear, RPR-Syphilis, patch test
tx balanitis
Improved personal hygiene, use of low to medium potency topical steroid until improved
Unique group of fungi capable of infecting nonviable keratinized cutaneous structures
Dermatophyte
Dermatophyte can infect what parts of the body?
- Stratum corneum
- Nails
- Hair
Arthrospores can survive in human scales for ?
12 months
3 genera of dermatopytes
- Trichophyton (MC) - Hair and nail
- Microsporum
- Epidermophyton
Dermatophytes - Scalp MC in who
Children
Dermatophytes transmission
- Person to person (MC)
- Animals
- Soil (least common)
pathophys Dermatophytes
dermatophytes produce enzymes (keratinases) that break down keratin allowing fungi to invade epidermis, nail and hair shaft
tinea pedis
feet
tinea cruris
groin
tinea corporis
trunk/extremities
tinea manuum
hands
tinea facialis
face
tinea capitis
hair
tinea barbae
facial hair
onychomycosis
nails
classifications of Dermatophytes
- Person to person = anthropophilic
- Animal to human = zoophilic
- Environmental = geophilic
predisposing factors for Dermatophytes
- atopy, ichthyosis
- collagen vascular disease - RA, SLE, temporal arteritis, scleroderma
- steroid use (oral/topical)
- sweating, local occlusion
- occupational exposure
dx options for Dermatophytes
Dx testing direct microscopy
-
Skin & Nail for KOH
- Skin - use a blade to scrape skin cells from area
- Nail - use a dull scalpel to remove excess keratin from nail
- Hair - remove hair at root -
Woods lamp - “black light”
- Blue green fluorescence = Microsporum - fungal cx
- Dermatopathology via skin biopsy
how to perform KOH
- 2 drops of 10% KOH to glass slide - sit for 15 min
- Inspect under low and high power
- hyphae and spores will be present
Dermatophytes how to collect for fungal cx
- skin: specimen obtained with brush (tooth or cervical brush)
- hair: specimen remove 5-10 hairs with forcep/hemostat at one time, use brush to obtain scales, use brush to inoculate fungal medium.
- nail: use fingernail clipper or sharp curette to obtain keratinous debris from under nail
place specimen inside a fungi culture medium
pros and cons of fungal cx for dermatophytes
- Limitations - requires days-wks to return definitive diagnosis
- Benefits - differentiates between fungal spp.
pros and con for skin bx for dermatophytes
- Benefits - most sensitive form of diagnosis
- Limitations
- skin biopsy sample required
- more invasive testing
topical antifungals for dermatophytes
Imidazoles
- Clotrimazole (Lotrimin)
- Miconazole (Micatin)
- Ketoconazole (Nizoral)
Allylamines
- Naftfine (Naftin)
- Terbinafine (Lamisil)
Systemic Treatment for Dermatophytes
(CBC, Cr, LFT’s)
Systemic PO agents
- Imidazole
- Itraconazole
- Ketoconazole
- Fluconazole - Allyamine
- Terbinafine ***
tinea capitis is MC in who
MC in children
MC in AA
presentation of Ectothrix occurring outside the hair shaft
Tinea Capitis
“grey patch” = scaly
Circular = hairs broken off = very brittle
Three presentations of Endothrix = occurs within the hair shaft
Tinea Capitis
- “Black dot”
- Kerion
- Favus
noninflammatory tinea capitis
- Scaling
- Pruritus
- Alopecia
- Adenopathy
flammatory tinea capitis
Pain
Tenderness
Alopecia
what are the “black dots” in tinea capitis
Broken off hairs near the scalp = swollen hair shafts
- Dots occur because broken hairs at the scalp
- Diffuse and poorly circumscribed
- Caused by: T. tonsurans, T. violaceum
what is Kerion in tinea capitis
- Inflammatory mass in which remaining hairs are loose
- Boggy, purulent, inflamed nodules, and plaques
- Painful = drains pus from multiple openings
- Hairs do not break off but fall out or pulled without pain
- Crusting and matting of surrounding hairs
- Caused by: T. verrucosum; T. mentagrophytes
- Heals with scaring alopecia
Latin for honeycomb
Perifollicular erythema and matting of hair
Thick/yellow crusts
Odor
Doesn’t clear spontaneously
Results in scarring alopecia
Favus - Tinea Capitis
dx Tinea Capitis
- Woods Lamp - T. tonsurans does not fluoresce
- Direct microscopy
- Fungal cx - growth seen in 10-14 d
- Bacterial cx - r/o bacterial with staph
Tinea Capitis w/o tx can lead to ?
permanent hair loss
tx tinea capitis
PO antifungals:
Terbinafine 250mg QD x 4-6 weeks
Griseofulvin 20-25mg/kg/day x 4-6 weeks
Antifungal shampoos - Ketoconazole 2% shampoo QD
prevention tinea capitis
- Wash clothing, bedding, and towels
- Wash furniture if in contact
- Avoid used pillow cases
- Avoid head to head contact
- Disinfect combs and other hair products
“Jock Itch”
Inguinal folds = thighs
Subacute or chronic dermatophytosis of the upper thigh and adjacent inguinal and pubic regions
Tinea Cruris
Tinea Cruris MC in who?
MC in males
Co-exists with Tinea Pedis typically
Large scaling, well demarcated dull red/tan/brown plaques
Central clearing
Papules and pustules @ margins
Tinea Cruris
dx tinea crusis
clinical
tx tinea cruris
- Topical antifungal x +/- 3 weeks
- Ketoconazole
- Econazole
— Zeasorb AF powder - PO Antifungals if failure of topicals
- Griseofulvin 375-500 mg daily x 2-4 weeks
management/prevention tinea cruris
- Wear shower shoes while bathing
- Put on socks before pants
- Antifungal/drying powders
- Benzoyl peroxide wash
- Alcohol based sanitizer gels
- Avoid tight fitted clothing/use cotton underwear
Fungal/dermatophyte infection involving anywhere on the body
**wrestlers infection
Tinea Corporis
aka ring worm
dx tinea corporis
clinical
bx if unsure
Can be asx
Pruritus depending on area
Sharply marginated plaques
Vesicles and papules
Central clearing
Tinea Corporis
tx Tinea Corporis
- Topical antifungals
- Oral antifungals (large surface area)
- Terbinafine 250 QD x 4 weeks
— CBC, Cr, LFT’s
Erythema
Scaling
Maceration
+/- bullae formation
MC dermatophyte infection athlete’s foot
Tinea Pedis
if tinea cruris is dx, what other body part do you need to check?
feet - Tinea Pedis
Tinea Pedis MC in what age group?
20-50y
RF Tinea Pedis
hot, humid climate, occlusive footwear, hyperhidrosis
4 subtypes of tinea pedis
- Interdigital
- Moccasin
- Inflammatory
- Ulcerative
Dry scaling
Maceration
Fissuring
Hyperhidrosis is common
MC site = between 4th and 5th toe
which type of Tinea Pedis
Interdigital Type
Well demarcated
Scaling with erythema
Papules at margin
Fine white scale
Hyperkeratosis
MC on soles or lateral border of feet
MC bilateral
which type of tinea pedis
Moccasin Type
Vesicles or bullae with clear fluid
Pus usually indicates secondary bacterial infection
After rupture erosions with ragged ringlike border
ID reaction can occur
MC on sole, instep, and web spaces
which type of tinea pedis
inflammatory
Extension of interdigital tinea pedis onto the plantar and lateral foot
May have secondary bacterial infection S. aureus
which type of tinea pedis
ulcerative
tx tinea pedis
- Topical antifungal
- BID x 2-4 weeks
- Ketoconazole & Econazole BID - Oral antifungal - Best for hyperkeratotic
- Terbinafine 250 mg QD x 2-6 weeks
- ALL SYSTEMICS = BLOOD WORK (Cr, LFT’s, CBC)
prevention tinea pedis
- Wash with BPO daily
- Use antifungal powder (Zeasorb AF)
- Shower shoes in communal showers
- Alcohol based sanitizers
T/F: Pityriasis Versicolor is part of the group cause dby deramtophyte
Tinea Versicolor
F, it is not
Tinea Versicolor MC in who
adolescents
Tinea Versicolor is an overgrowth of?
Malassezia furfur
Seen often in patients with oily skin (thrives in this environment)
RF tinea versicolor
- Climate
- Sweating
- Immunodeficiency
- Products
- Steroid use
- Oily skin
is tinea versicolor contagious?
no
s/s tinea versicolor
clinically asx
- Patient can experience some itching possibly psychological
- Patient usually complains about the appearance
- Macules +/- scale
- Patches +/- scale
- Plaques +/- scale
— Hypo/hyperpigmentation
— Erythema
dx tinea versicolor
- KOH shows hyphae and budding yeast (spaghetti and meatballs)
- Woods light
tx tinea versicolor
- Selenium sulfide or zinc pyrithion
- Topical antifungals ketoconazole
- PO therapy not recommended unless failure of topicals