Skin and Soft Tissue Infections

Question 1

1. Describe the characteristics and the organisms associated with erysipelas.

Answer 1

classic erysipelas: involves the dermis, caused by Strep. pyogenes presenting with striking erythroderma, with induration, a sharply demarcated raised border, regional adenopathy and pain, managed with oral antibiotics (Penicillin VK)

Question 2

1. Describe the characteristics and the organisms associated with cellullitus.

Answer 2

classic cellulitis: deep infection involving the subcutaneous fat layer presenting with soft tissues red, hot, swollen and often painful, regional adenopthy is common and wide range of severities managed in a variety of ways

(less striking, less distinct borders)

Question 3

1. Describe the characteristics and the organisms associated with life-thretening skin and soft tissue infections including necrotizing fasciitis.

Answer 3

subcutaneous infection that tracks along fascial planes and extends beyond superficial signs of infection (commonly extremities, anterior abdominal wall, perineum, perianal area, surgical wounds)
patients with necrotizing skin and soft tissue infections require prompt and aggressive surgical debridement in order to survive, antibiotics alone cannot clear these infections

Question 4

2. Describe the impact of synergistic infection on the outcome of a deep soft tissue infection.

Answer 4

aerobic bacteria causing tissue destruction that leads to devitalized tissue and an anaerobic environment that allows anaerobic bacteria to thrive

Question 5

3. Describe the factors involved in recurrent cellulitis and the treatment strategies that are important in terms of decreasing the risk of future episodes.

Answer 5

vigorously treating predisposing factors (compression stockings, antifungals etc.)
and using long-term antibiotic prophylaxis (low dose penciling VK, erythromycin, dicloxacillin or clindamycin)

Question 6

4. Describe the clinical features that suggest the presence of a life-threatening skin and soft tissue infection.

Answer 6

pain out of proportion to appearance of skin
systemic toxicity (abnormal vitals, elevated anion gap, multi organ failure, TSS)
rapid progression
necrosis of the skin, gangrene, bullae formation, cutaneous hemorrhage, crepitus
anesthesia of involved (nerve supply infarcted)

Question 7

Contrast non purulent and purulent cellulitis based on physical characteristics and causative agent

Answer 7

non purulent cellulitis caused by beta-hemolytic streptococci, especially Group A strep

purulent is associated with a cutaneous abscess and S. aureus is the major pathogen, MRSA and CA-MRSA leading the causes

Question 8

What are the most common associations with the following populations and causative agents for soft tissue infection?

fresh water trauma
salt water trauma
fish handlers/butcher
periobital
living in close contact with others
immune compromised
fish tank
dog/cat bite

Answer 8

fresh water trauma: Aeromonas hydrophila
salt water trauma: Vibrio species
fish handlers/butcher: Erysipelothrix
periobital: S. aureus > GAS over age 5
living in close contact with others: CA-MRSA
immune compromised: aerobic gram-negative rods, fungi, mycobacterial
fish tank: Mycobacterium marinum
dog/cat bite: Pasteurella multocida

Question 9

What are common portal of entry for cellulitis infection?

Answer 9

tine pedis
eczema
psoriasis
furuncles
ulcers
trauma
(portal may not be evident)

Question 10

Which is the component/symptom of cellulitis that needs to be prioritized when addressing cellulitis?

Answer 10

lymphedema: limbs that are affected by chronic, non-resoluving lymphedema have an increased risk of cellulitis (common causes: venous insufficiency, prior surgery, radiation, DVT, allergic or congenital causes, prior episodes of cellulitis)

Question 11

What are the key steps in management of uncomplicated cellulitis?

Answer 11

1. ID purulent v. non purulent.
2. take hx. of epidemiological clues to ID unexpected pathogens
3. appropriate management of portal of entry
4. manage lymphedema (raise effected area)
5. Culture any blister fluid, pus, abscess, blood culture, sometimes nasal swab
6. select appropriate antibiotics

Question 12

Contrast drugs that you would use for purulent cellulitis v. non-purulent

Answer 12

purulent: TMP/SMX, doxycycline/minocyclin, clinamycin, linezolid;; vancomycin, daptomyin, clindamycin or ceftaroline

non-purulent: Pen VK, amoxicillin, dicloxacillin, cephalexin, clindamycin;; nafcillin, penicillin, cefazolin, clindamycin or vancomycin

Question 13

Describe the characteristics and the organisms associated with life-thretening skin and soft tissue infections including necrotizing fasciitis, gas gangrene (specifically details about Fournier Gangrene and clostridial gas gangrene - location, risk, organisms)

Answer 13

FG: involves the perineum in men and women, (esp. diabetic populations) with mild infection or trauma that can spread infection to subcutaneous tissues and base of the scrotum or anterior abdominal wall through fascial planes

higher rate of Pseudomonas aeruginosa as a mixed infection

C. perfringens is the most common cause of gas gangrene, associated with trauma and toxin mediated characterized by severe pain, tense edema, fluid filled bullae, purplish hue to skin, thin “dirty dishwater” drainage and gas in soft tissues, tx. with penicillin and clindamycin

Question 14

Describe the characteristics and the organisms associated with life-thretening skin and soft tissue infections including necrotizing fasciitis, polymicrobial infections of the diabetic foot.

Answer 14

clinical setting include: penetrating abdominopelvic trauma, GI tract surgery, pressure ulcers, perianal abscess, injection drug use site, spread of infections from the perineum, diabetic foot ulcers

chronic foot ulcers in DM neuropathy are associated with complex polymicrobial colonize ion of a variety of bacteria (Strep, Enterococci, Staph, aerobic gram neg. anaerobes)
tx. involves broad spectrum coverage

Question 15

Describe the characteristics and the organisms associated with disease concerns specific to neutropenia.

Answer 15

severe forms of routine pyogenic infections, presentations of unusual organisms or disseminated infection

important to make a specific microbiological diagnosis

Neutropenic- Ecthyma granrenosum: cutaneous vaculitis that occurs in association with Pseudomonas (painless red macule rapidly evolve into painful necrotic lesion

with cutaneous mycosis, always look hard for dissemination and broad spectrum antibiotics including MRSA and Pseudomonas coverage

Question 16

Describe the characteristics and the organisms associated with infections associated with bite wounds.

Answer 16

human bites contain oral bacterial flora (Strep, staph, H. spp. Eikenella corrodes and anaerobes, Hep B, C syphilis, herpes, and HIV

clenched fist injuries are esp prone to deep inoculation and risk of bone and joint seeding– tx. wound irritation and tetanus toxic, antibiotics regardless of wound appearance (amoxicillin clavulante or flouros with clindamycin)

cat and dog bites: additionally Pasteurella multocida, Capnocytophaga canimorsus; cat bites are usually more severe and deeper: tx. with irrigation but not closed, antibiotics in all cases (same as above fluros or cefuroxime)

Question 17

Name the top 3 mono microbial necrotizing fasciitis causative organisms.

Answer 17

Group A strep: high mortality, often secondary to minor injuries, tx. penicillin + clindamycin

S. aureus- esp. CA-MRSA

Vibrio vulnificus: common with salt water, shellfish, plankton causes rapidly progressive infection often with large blisters and ulceration (esp with cirrhosis or impaired cellular immunity)

Question 18

Describe the characteristics and the organisms associated with disease concerns specific to CMI impairment.

Answer 18

increased risk of gram positive and gram negative bacteria AND atypical myobacteria, nocardia, crytpococcus, disseminated hitoplasmosis or coccidioidomycosis, varicella-zoster virus, herpes- simplex virus, cytomegalovirus and strongyloids

biopsy skin lesion and look for dissemination