ILE XI: SSTI

What are risk factors for skin infection?

- Reduced skin integrity

- Excess moisture

- Poor blood supply

- High bacterial load

Describe Cellulitis

Red, diffuse, flat lesion with an irregular border

What layer of the skin is involved in cellulitis?

Epidermis, dermis, and subQ fat

What is the most common pathogen in nonpurulent SSTIs?

Strep. Pyogenes

What is the ~general~ treatment for mild nonpurulent infections?

PO ABX

Describe mild nonpurulent infections.

Typical presentation with no purulent focus

Describe moderate nonpurulent infections.

Typical presentation with systemic signs of infection (fever, chills, elevated WBC)

What is the ~general~ treatment for severe nonpurulent infections?

Emergent I&D

Empiric ABX

C&S

Describe severe nonpurulent infections.

Failed oral ABX

Systemic signs of infection

Immunocompromised

Hypotensive

Clinical signs of deeper infection

What are the specific drugs used in the empiric treatment of severe nonpurulent cellulitis?

No personal/household history of MRSA= Cefazolin

personal/household history of MRSA= Vancomycin

Why is clindamycin used in the treatment of SSTIs?

Primarily for penicillin allergies

What is the most common pathogen in purulent SSTIs?

S. aureus

Describe mild purulent infections.

Typical cellulitis with purulence but NO systemic signs of infection

What is the ~general~ treatment for mild purulent infections?

I&D

Describe moderate purulent infections.

Typical cellulitis with purulence + systemic signs of infection (fever, chills, elevated WBC)

Multiple sites of infection

Extreme age

Immunosuppression

Abscesses on hands/face/genitalia

What is the ~general~ treatment for moderate purulent infections?

I&D

C&S

PO Abx

Describe severe purulent infections.

Failed I&D PLUS oral ABX

Presence of SIRS

Immunocompromised patients

What is SIRS criteria?

Two or more:

- T > 38 C

- Pulse > 90

- RR > 24

- WBC < 4000 or > 12000

What is the ~general~ treatment for severe purulent infections?

Emergent I&D

Empiric ABX

C&S

What are the specific drugs used in the empiric treatment of mild- mod purulent cellulitis?

TMP/SMX, Doxycycline, Clindamycin (if MRSA susceptible)

What are the specific drugs used empirically in the treatment of severe purulent cellulitis?

vancomycin, TMP/SMX, Clindamycin (if MRSA susceptible)

TMP/SMX MOA

Inhibits bacterial folic acid synthesis

Which relevant bugs are susceptible to TMP/SMX?

S. aureus including MRSA

Unreliable against S. pyogenes

TMP & SMX - Bacteriostatic or Bactericidal?

Bactericidal

TMP/SMX Excretion

Urine

TMP/SMX ADRs

HSR, AKI, kidney stones, hyperkalemia, photosensitivity, agranulocytosis, thrombocytopenia, leukopenia

TMP/SMX Drug Interactions (6)

Warfarin: increases INR

K Sparing Drugs: hyperkalemia

Sulfonylureas: increased TMP/SMX concentration

Phenytoin: increased TMP/SMX concentration

Dofetilide: increased TMP/SMX concentration

Azathioprine/MTX: increased TMP/SMX concentration

TMP/SMX Contraindications (4)

- Sulfa Allergy

- History of sulfa-induced immune thrombocytopenia

- Anemia due to folate deficiency

- Infants < 4 weeks

TMP/SMX Warnings

- Blood dyscrasias

- Rash (SJS)

- Hemolytic anemia due to G6PD deficiency

TMP/SMX Pediatric Dosing

8-12 mg/kg/day BID x 5 days

Always dose TMP

TMP/SMX Monitoring

Renal function, LFTs, electrolytes (K), CBC

TMP/SMX Pediatric Considerations

Solution is 40 mg/5 mLs

Shake suspension

Flavored well

Clindamycin MOA

Inhibits 50s ribosomal subunit and suppresses protein synthesis

Which relevant bugs are susceptible to Clindamycin?

Strep species

S. aureus including some MRSA

Clindamycin: Bacteriostatic or Bactericidal?

Bacteriostatic

Clindamycin Excretion

Bile; hepatic dysfunction is a concern

How is MRSA susceptibility to Clindamycin confirmed?

Negative D-test

Clindamycin Pediatric Dosing

25-30 mg/kg/day PO every 8 hours

25-40 mg/kg/day IV every 8 hours

30 mg/kg/day

Round down for oral and up for IV

Clindamycin Notable ADRs

GI Distress

Skin rash

Clindamycin BBW

Severe colitis (C. diff)

Clindamycin Contraindications

Hypersensitivity

Clindamycin Pediatric Considerations

Comes in capsule and oral solution

Oral solution is cherry flavored and has a bad aftertaste

Can sprinkle the capsule

Recommend adding pre or probiotic

Return to ED if fever +/- severe GI upset (C. diff)

Tetracyclines MOA

Inhibit bacterial RNA synthesis by binding to the 30s ribosomal subunit

Which relevant bugs are susceptible to Tetracyclines?

S. aureus including MRSA, Streptococcus

Tetracyclines: Bacteriostatic or Bactericidal

Bacteriostatic

Tetracyclines Notable ADRs

GI distress, phototoxicity

Tetracyclines Warnings/Precautions

- Not recommended in children under 8 due to bone growth slowing

- Photosensitivity

- Renal toxicity

Tetracyclines Important Counseling Points

Separate products with divalent or trivalent cations 1 hour before or 2 hours after Tetracyclines

- Dairy

- Antacids/calcium supplements

- Fe or Zinc supplements

- Bismuth subsalicylate

Doxycycline Pediatric Dosing

100 mg PO every 12 hours