Skin and Soft Tissue Infections (3-1-22) Flashcards by Joanne Song

What bacteria is the most common cause of skin and soft tissue infections?

Most common

) Beta-hemolytic streptococci
) Coagulase negative staphylococcus aureus

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Why is staph and strep the most common bacteria that cause skin and soft tissue infections?

Because on the normal skin flora are staph and strep. Thus, if you have any cut in the skin, these bacteria can get deeper into the skin and cause an infection

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Why is it important to get a history for pts with skin and soft tissue infections?

B/c this way you can figure out what the bacteriology of the SSTI is and the patient risk

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What is impetigo? On what body part do you usually see it?

Superficial skin infection of the epidermis consisting of papules when ruptures, form a dried honey colored crust

See on skin of face and extremities

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Impetigo symptoms?

Have bullous that rupture and leave a sometime itchy or painful honey colored crust.

Non bullous is more common than bullous

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What organisms are more likely to cause non-bullous or bullous impetigo?

Non-bullous –> Group A strep or MSSA

Bullous –> MSSA

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How does impetigo happen? Pathogenesis

If there is a cut or abrasion, an organism can directly invade healthy skin or get into the superficial layers of the skin

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Which is more contagious, impetigo bullous or non-bullous?

non-bullous

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What patients are at the highest risk of getting impetigo?

) CHILDREN
) have skin trauma
) hot/humid clincates
) poor hygiene
) day care settings
) crowding
) malnutrition
) diabetes

make sense why children are at high risk

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What are the organisms that cause Impetigo?

1.) Staph aureus
AND/OR
2.) Strep pyogenes (group A streptococcus)

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How do you know if you have impetigo?

Look at clinical presentation: Have a honey colored crust discharge

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How can you treat impetigo if mild?

Give topical mupirocin 2% or retapamulin 1% ointment BID x 5 days

can also resolve spontaneously

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How can you treat more “severe” impetigo? (want to prevent new vesicle formation, decrease transmission, transitioned to crusted phase)

Systemic PO antibiotics:

) Dicloxacillin (1st line)
) Cephalexin
) Erythromycin
) Clindamycin
) Amoxicillin/clavulanate

if have beta lactam allergy can go to erythromycin or clindamycin

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What is cellulitis?

Acute spreading infection that involves the epidermis, dermis, and SQ tissue without fascial involvement –> thus can reach bloodstream –> so get systemic SE

outpatient or inpatient

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Where do you most often see cellulitis ?

Lower extremities –> only one one extremity not both

but depending on risk factors or where disruption of skin is, you can see it anywhere

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Symptoms of cellulitis?

Rapid spreading of redness, tenderness, warmth, and swelling in skin with POORLY DEFINIED border

Fever, malaise, leukocytosis

How does one get cellulitis?

Due to trauma, wounds, Athlete’s feet, dry/crack skin, injection drug use, ulcers, or surgery, the organisms can get in through there

Patients at risk of cellulitis?

) normal hosts (anyone)
) diabetes –> b/c of neuropathy, vascular changes, dry/cracked skin
) injection drug users
) pts with arterial or venous insufficiency
) obese pts
) pts with lymphedema
) immunocompromised pts

What is erysipelas

A type of cellulitis caused by B-hemolytic streptococci involving only the upper dermis and superficial lymphatics with intense erythema and CLEARLY defined border. Also has the peau d’ orange

What are the unique symptoms of erysiplas?

Clearly defined borders and the peau d’ orange (orange peel) appearance due to edema surround the hair follicles

Where is erysipelas mostly seen on body?

FACE

What are the common bacteria causes of cellulitis?

) beta hemolytic strep (s. pyogenes)
) Staph aureus (including MSSA)

For injection drug users also included MRSA

When would you suspect MRSA with Cellulitis?

Injection drug users
penetrating trauma
evidence of MRSA infection else where
Purulent cellulitis (abscess)
SIRS

Empiric treatment for Mild diabetic foot infection?

Cephalexin PO
Dicloxacillin PO
Amoxicillin/clavulanate PO

If MRSA suscepted:
- Clindamycin or Bactrim PO

What is the likely causative organisms for mild diabetic foot infection?

- Beta-hemolytic strep - Staph aureus Possible for MRSA as well (if previously MRSA infection/colonization, or if local prevalence of MRSA is high)

What are the likely causative organisms for moderate diabetic foot infection?

- Beta-hemolytic Strepococcus - Staphylococcus aureus (MSSA or MRSA if have risk factors) - Consider enterobacteriaceae if they have been on an antibiotic in past 30 days - Consider obligate anaerobes if they have a necrotic wound that has not been debrided

What are the risk factors for MRSA in diabetic foot infection?

- If have high local prevalence of MRSA - Prior history of MRSA infection/colonization - Severe infection

What is the empiric treatment for moderate DFI?

- IV cefazolin (or vancomycin if have suspected MRSA) - IV ceftriaxone alone if suspected enterobacteriaceae - Add PO metronidazole if anaerobes are suspected

What are the common causative organisms for severe diabetic foot infection?

- Beta-hemolytic strep - staph aureus (MSSA and MRSA) - Enterobacteriaceae - Pseudo. aeruginosa - Anaerobes

What are empiric therapy options for severe diabetic foot infection?

Vancomycin PLUS Zosyn or meropenem OR Ceftazidime or cefepime + PO metronidazole OR Levofloxacin or ciprofloxacin + PO metronidazole

What is the treatment for empiric necrtizing fascilitis?

1. ) need to do surgery to remove debrided necrotic wound 2. ) Vanc + meropenem OR vanc + zosyn 3. ) Add clindamycin Need to do in this order

What is targeted therapy for necrotizing fascilitis?

Strep pyogenes --> penicillin Staph aureus --> nafacillin or oxacillin (MSSA) MRSA --> vancomycin

Where does necrotizing fascilits affect? Layers?

Lower extremities, lower abdomen, genital area Fascia and SC muscle/fat

How do you know if you have DFI?

Must have 2 or more of following: - Swelling/induration - Erythema - warmth - Pain - Tenderness - Purulent discharge Systemic signs (fever, tachycardia, leukocytosis)

What is conisdered as mild DFI?

1.) cellulitis extends < 2 cm from border of ulcer. Has NO SIRS Usually limited to superficial tissue

What is considered as moderate DFI?

Cellulitis extends >2 cm from border of ulcer OR Involves deeper tissue such as (abscess, septic arthritis, osteomyelitis, fasciitis, cellulitis) WITHOUT SIRS

What is considered as severe DFI?

Local infection with signs of 2 or more of SIRS: 1. ) Temp > 38 C 2. ) HR > 90 3. ) RR > 20 4. ) WBC > 12,000 5. ) Bands > 10%