Bacterial Skin and Soft Tissue Infections Flashcards
Describe impetigo. What are the characteristic features? How do you treat it?
-superficial infection of the skin, usually due to Strep progenies
-intraepidermal
-vesicopustular lesion,
-main characteristic: golden crusts
-most common during hot, summer months
Tx: Penicillin or cephalosporins
-topical mupirocin or retapamulin
What are the characteristics of bullous impetigo?
- caused by S. aureus, exfoliative toxins
- mainly newborns and young children
- Vesicles become flaccid bullae, rupture and leave light brown crusts
- Rare fever and constitutional symptoms
- 10% cases of impetigo are bullous
What are the characteristics of Erysipelas?
Superficial cellulitis prominent lymphatic involvement Lesions bright red, edematous, indurated (“peau d’orange”) with a sharp, raised border Due to Group A streptococcus More common at the extremes of age infants, young children, older adults Location 70-80% of lesions on lower extremities 5-20% on face Predisposing factors: venous stasis, diabetes mellitus, alcohol abuse, nephrotic syndrome, local edema/lymphatic obstruction (e.g., after a radical mastectomy) Therapy: systemic penicillin
What are the characteristics of folliculitis?
Pyoderma located in hair follicles and apocrine regions
Small erythematous papules topped by central pustule
Commonly found on hips, buttocks, axilla
Organisms:
S. aureus most common
Pseudomonas aeruginosa associated with swimming pools and whirlpools
What are furuncles and carbuncles?
Furuncle (boil):
deep inflammatory nodule, usually developing from a preceding folliculitis
S. aureus usually the pathogen
Carbuncle
multiple abscesses, separated by connective tissue septae, draining to the surface along hair follicles
S. aureus usually the pathogen
What is the therapy for furuncles and carbuncles?
Therapy Warm compresses Systemic antibiotics directed against Staphylococcus aureus Now concern for CA-MRSA Surgical drainage often necessary Prevention of recurrent disease General body wash (chlorhexadine) Nares decontamination (mupirocin)
What are the characteristics of abscesses?
Localized collection of pus
Usually due to S. aureus
CA-MRSA (pvl producing) very common
Less commonly to Streptococcus spp.
Injection site abscess (intravenous drug users)
S. aureus, Streptococcal spp., gram negative rods (Enterobacteriaceae), anaerobes
Often polymicrobial for IVD users
What are the characteristics of cellulitis? How do you treat?
Acute, spreading infection of the skin extending deeper than erysipelas to involve the subcutaneous tissues
Most frequent causes
Group A streptococcus
S. aureus
Therapy
Elevation of infected extremity
Antibiotic therapy that covers GAS and S. aureus
What are the signs of necrotizing soft tissue infections?
Edema > erythema Skin vesicles or bullae Subcutaneous gas No lymphangitis or lymphadenitis PAIN!
How do you diagnose necrotizing soft tissue infections?
Clinical findings Laboratory testing Of little use; lacks sensitivity and specificity Ultrasound MRI scan SURGERY
What is the therapy for necrotizing STI?
Prompt recognition
Urgent debridement
Broad-spectrum antibiotics
Supportive care
How should animal bite wounds be treated? What bacteria are associated?
Wounds should be cleaned and left open Antibiotics 3-5 days for contaminated wounds >5 days for established infection Rabies not a threat currently from domestic dogs Microbiology Polymicrobial infections (avg 5) S. aureus, streptococci, mouth anaerobes, GNR Dogs: Pasturella canis Cats: Pasturella multocida
How should human bite wounds be treated?
Polymicrobial infections usually due to Eikenella corrodens, S. aureus, Streptococcus spp. and anaerobes Wounds should be cleaned and left open Antibiotics 3-5 days for contaminated wounds >5 days for established infection
What are the characteristics of the primary and secondary stages of syphilis?
Primary stage Ulcerated papule in 1-2 weeks, chancre Identify organism by darkfield exam Serology is positive Secondary Syphilis At 4-8 weeks widely dispersed organisms Widespread maculopapular involves the palms and plantar surfaces Latent Serologic proof of infection without disease Can last years Tertiary 3-15 years after infection Gummatous syphilis Late neurosyphilis Cardiovascular syphilis
List the four types of superficial mycoses?
pityriasis versicolor, tinea nigra, white piedra, black piedra
What are the characteristics of pityriasis (tinea) versicolor?
More common in tropics or with sun exposure Scaly macules Hypo- or hyperpigmented On trunk and proximal limbs Non-pruritic (not itchy) -Pathogen: Malassezia furfur Normal commensal on the skin Produces azaleic acid in stratum corneum associated with depigmentation
How do you diagnose tinea versicolor?
Clinical
Typical lesions
Lesions fluoresce yellow-green under Wood’s light (UV, 365 nm)
Direct microscopy of lesion scrapings
KOH prep or staining with Parker Quink ink
short hyphae and yeast-like cells (“spaghetti and meatball”)
What are the organisms and characteristics associated with tinea nigra, white piedra, and black piedra?
tinea nigra - exophiala wernecki -black macules
white piedra - trichosporon beigelii -creme colored nodules on hair shaft
black piedra - piedraia hortai - black nodule on hair shaft
What are the tinea/dermaphyte infections based on their anatomic sites?
Tinea \_\_\_\_ pedis -feet capitis- scalp manus - hands unguim - nails corporis - body cruris -jock itch barbae - beard
How are tinea infections diagnosed?
Wood’s lamp Scalp infections due to Microsporum species fluoresce green Trichophyton infections do not fluoresce Microscopic examination of KOH look for hyphae Culture Identify species of dermatophyte
When do tinea infections require systemic therapy?
- hair and nail infections
- widespread tinea corporis
What are the common causes of onychomycoses? (fungal nail infections)
Scopulariopsis brevicaulis
Leading non-dermatophyte cause of onychomycosis
Candida albicans
Leading yeast cause
May have >1 fungus species causing the infection
What is a cutaneous syndrome caused by candida? What are its characteristics?
Intertrigo
Common condition
Affects any site where skin surfaces are in close proximity and there is a warm, moist environment
Begins as vesicopustules, which enlarge and rupture causing maceration and fissuring
scalloped border with a white rim of necrotic epidermis, surrounding an erythematous, macerated base
Satellite lesions are often seen
What are the three genera of dermatophytes and where do they infect?
Trichophyton - skin, hair, nails
Microsporum - skin, hair
Epidermophyton - skin, hair
