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Skin and Soft Tissue (SST) Infections

Skin and Soft Tissue (SST) Infections. Michael J. Tan, MD, FACP, FIDSA Associate Professor of Internal Medicine Northeastern Ohio Universities Colleges of Medicine and Pharmacy Summa Health System, Akron, OH.

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Skin and Soft Tissue (SST) Infections

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  1. Skin and Soft Tissue (SST) Infections Michael J. Tan, MD, FACP, FIDSA Associate Professor of Internal Medicine Northeastern Ohio Universities Colleges of Medicine and Pharmacy Summa Health System, Akron, OH

  2. A 47 year old known IV drug abuser presents to the ED with a painful swollen arm of 8 hours duration. Swelling has extended from the antecubital area to the entire arm in 2 hours. Which of the following is appropriate therapy? • A. Initiate vancomycin alone • B. Call the surgeon for immediate debridement • C. Treat with IVIG alone • D. Aspirate the antecubital area • E. None of these is appropriate

  3. Objectives • Review types of common skin and soft tissue infections • Recite common pathogens associated with these infections • Review diabetic foot infections • Understand treatment modalities and antimicrobials used for these infections

  4. Bacterial Skin and Soft Tissues Infections • Primary Pyoderma • Impetigo, erysipelas, folliculitis, carbuncles • Infections secondary to pre-existing conditions • Surgical wounds, trauma, bites, decubitus infections, diabetic foot infections • Necrotizing infections • Polymicrobial • Monomicrobial (Gp A. Strep; Clostridium)

  5. Bacterial SST Infections • General Approach to therapy • Antimicrobial therapy • Directed against likely pathogens • Common organisms • Specific pathogens based on epidemiology • Emerging antimicrobial resistance • Community-Onset MRSA, macrolide resistant S pyogenes • Healthcare-associated pathogens • Surgical Incision and drainage, debridement, excision

  6. Bacterial SST Infections • Practice Guidelines for the Diagnosis and Management of Skin and Soft-Tissue Infections • Infectious Diseases Society of America (IDSA) • IDSA Guidelines. Stevens D et al. Clin Infect Dis 2005;42:1379-406

  7. Bacterial SST Infections • General Considerations • Diverse Etiologies • Depends on epidemiological setting • Immune status • Geographical locale • Trauma or Surgery • Prior antimicrobials (resistance) • Lifestyle • Animal exposure IDSA Guidelines. Stevens D et al. Clin Infect Dis 2005;42:1379-406

  8. Bacterial SST Infections • Management • Diagnosis • Clinical findings • Biopsy • Assessment of severity of infection • Therapy • Antimicrobial therapy • Surgical debridement/excision IDSA Guidelines. Stevens D et al. Clin Infect Dis 2005;42:1379-406

  9. Bacterial SST Infections • Severity of Infection • Evaluate for systemic toxicity • Fever, tachycardia, hypotension • Consider need for hospitalization if: • Hypotension, increased creatinine or CPK, decreased bicarbonate (acidosis), CBC with left shift • Severe, deep infection, or necrotic infection IDSA Guidelines. Stevens D et al. Clin Infect Dis 2005;42:1379-406

  10. Mimics of Material Skin and Soft Tissue Infections • Acute allergic reaction • Contact dermatitis • Toxin (eg chemical) • Trauma • Thermal reaction (hyper-, hypo-) • Acute gout

  11. Common Skin Infections (Primary Pyoderma)

  12. Community-associated MRSA 65 y/o female with a boil unresponsive to 3 days of cephalexin Photo courtesy of T. File MD

  13. CDC Definition of CA-MRSA • Diagnosis of MRSA made in the outpatient setting or by a culture positive for MRSA within 48h of hospital admission • Patient has no medical history of MRSA colonization or infection • Patient has no medical history in the past year of: • Hospitalization • Admission to a nursing home, skilled nursing facility or hospice • Dialysis • Surgery • The patient has no indwelling catheters or medical devices that pass through the skin www.cdc.gov

  14. Community-Associated (CA) MRSA • Increasing cause of community skin infections • Genotypically and phenotypically unique from nosocomial MRSA • Less resistant to non-beta-lactam agents • Often susceptible to TMP-SMX, clinda, tetracyclines, +/- fluoroquinolones • Panton-Valentine leukocidin (PVL) – virulence factor • Risk Factors • Athletes, inmates, military recruits, men who have sex with men, injection drug user, prior antibiotic use • Increases need to culture.

  15. 3/21/05 3/22/05 18 y/o male treated with amox/clav for ‘spider’ bite at local urgent care center. Photos courtesy of T. File MD

  16. Pyoderma-Antimicrobial Therapy • S. pyogenes • Beta-lactams; Others: macrolides (resistance 5-10%), clindamycin, doxycycline, minocycline • S. aureus • MSSA: antistaphylococcal penicillins (ie dicloxacillin, nafcillin, oxacillin); cephalosporins; clindamycin; macrolides; doxycycline, minocycline, TMP-SMX • MRSA • Hospital acquired: Vancomycin, linezolid, daptomycin • Community-associated: Trimethoprim-sulfamethoxazole; doxycycline/minocycline; clindamycin (if “D Test” negative) Modified from IDSA Guidelines. Stevens D et al. Clin Infect Dis 2005;42:1379-406

  17. INFECTIONS ASSOCIATED WITH UNDERLYING CONDTIONS • Infections • Post Op wound infections • Lower extremity cellulitis • Diabetic foot ulcers • Decubitus ulcers • Bite wound infections • Post Trauma infections • Perforated bowel Photo courtesy of T. File MD

  18. Bacteriology: SST Infections associated with underlying conditions • Gram positive cocci • S aureus • MSSA • MRSA (Hospital-acquired; community-acquired) • VIRSA, VRSA • Streptococcal spp (including GBS and other spp) • Enterococci (VRE) • Gram negative bacilli • Enterobacteriaciae • Pseudomonas sp • Anaerobes

  19. What can you expect? superficial Gram Positives GN Anaerobes Deep

  20. ANTIMICROBIAL ACTIVITY Agents Staph**/Strep GNB Anaerobes Nafcillin/Cefazolin + 0 0 Cefoxitin/ + +/-* + Cefotetan Amp/sulb (amox/clav) + +/-* + Pip/tazo; Ticar/C + + + Ertapenem + +* + Imipenem/Mero + + + FQ + Clinda (metronid) + + + * not for Pseudomonas ** If MRSA: Vancomycin (>99%), Linezolid (>99%), Daptomycin (>99%), [Others: Trim/sulf (60-80%), Minocin (90%),

  21. Diabetic Foot Infections 62 y/o postman with fever and draining foot ulcer Photo courtesy of T. File MD

  22. Diabetic Foot Infections • Predisposing Factors • Peripheral Neuropathy • Maldistribution of weight (trophic ulcers) • Failure to sense problems (corns, calluses) • Vascular insufficiency • Bacterial etiology • Early, superficial – Strep, Staph • Late, deep – Mixed • Therapy – Surgery and antimicrobial agents • Multi-disciplinary approach

  23. Post-Op 6 Weeks later Photos courtesy of T. File MD

  24. Effect of Early Surgery on SubsequentAbove Ankle Amputation(Tan JS et al. Clin Infect Dis 1996;23:286-291)

  25. Other Specific Skin Infections IDSA Guidelines. Stevens D. et al. Clin Infect Dis 2005;42:1379-406

  26. Necrotizing Skin Infections • Characteristics • Often perineal or lower extremity (especially for mixed infections) • Abnormal inflammatory response (less “purulent”) • Often rapidly spreading • Putrid discharge (what organisms?)/crepitance often present • Associated with • DM • Vascular disease • Trauma (bites included) • Surgery

  27. Necrotizing Skin Infections • Pathophysiology • Mixed aerobic/anaerobic infection • Synergistic infection • Presence of facultative organisms creates better anaerobic environment for anaerobes • Virulence factors of one organism assists another organism (anti-phagocytic effect of B. fragilis capsule) • Growth factors • Monomicrobial (eg Strep, Staph, clostridia) • Toxins • Enzymes

  28. S. aureus Polymicroibal

  29. Necrotizing Skin Infections • Manifestations • Tissue necrosis, spreading, bullae, severe pain, pain out of proportion, pain then no pain. • Often severe intensity of illness • Requires EXPEDITIOUS SURGERY. • Several anatomical syndromes • Eg necrotizing fasciitis; gas gangrene others • Cannot easily differentiate syndromes on basis of initial clinical presentation • Initial approach is similar: Early surgery and antibiotics • Microbiology • Mixed anaerobes/aerobes • Monomicrobial • Streptococcus pyogenes • Staphylococcus aureus • Clostridia sp (perfringens most common)

  30. Necrotizing Fasciitis • Microbiology: 2 Types • Type 1- polymicrobial (aerobic/anaerobic) ie diabetic foot infection, decubitus infection, bite wounds • Type 2 – S pyogenes (Strep toxic shock syndrome) • Characteristics • Erythema and swelling, bullae, gangrene • Type 1 may have a foul odor (mixed infection) • Initially severe pain, but as tissue necrosis progresses, the pain may disappear

  31. Diabetic woman with rapidly spreading gangrenous infection Photo courtesy of T. File MD

  32. Photo courtesy of T. File MD

  33. Infection 8 hours after amputation Photos courtesy of T. File MD

  34. Gas Gangrene due to C. perfringens Photos courtesy of T. File MD

  35. Clostridial skin infections • Clostridial cellulitis • Infection limited to the dermis and epidermis • Abundance of gas, usually not systemically ill • Clostridial myonecrosis (classic gas gangrene) • Rapid onset of necrosis, pain, and toxic state • Usually associated with devitalized tissue (trauma, surgery, peripheral vascular disease) • Clostridial toxins (alpha toxin) • Lyses blood cells and causes tissue destruction • Therapy – Immediate surgery, antibiotics +/- hyperbaric O2? • Clostridium septicum • Consider adenoCA of Colon, leukemia.

  36. Clostridial cellulitis Photo courtesy of T. File MD

  37. S pyogenes Necrotizing Fasciitis • Increasing frequency over past decade • Result of specific toxins-Streptococcal pyrogenic exotoxins (SPE). Causes release of cytokines (TNF), which can mediate fever, shock and tissue injury • Most cases sporadic (occasional secondary spread); often in normal host • Bacteremia ~50% • Mortality 20-40% • Therapy • Rapid surgery • Antibiotics

  38. Photo courtesy of T. File MD

  39. Necrotizing Fasciitis (NF) due to CA-MRSA • 14 cases of NF due to CA-MRSA from one center • Represented 29% of all cases of NF • 71% men; mean age 43; 40% bacteremic • 10/14 with coexisting medical problems • IVDU, DM, Hep C, Cancer, HIV Prior MRSA • Specimens showed few or no WBCs on gram stain • All susceptible to Vanc, TMP-SMX, clinda • All had complicated ICU courses; deaths • NEJM 2005;352:1445-1453

  40. Clues Suggesting NF vs. Cellulitis • Pain more severe than expected (followed by anesthesia) • Rapidly spreading swelling and inflammation • Bullae (but can be seen with cellulitis as well) • Necrosis • Toxic shock syndrome • Elevated CK • Risks: Varicella, NSAIDs

  41. Necrotizing Fasciitis • Diagnossis • CT/MRI • Edema along fascia • Direct inspection (surgical) • Swollen, dully gray, string • Thin exudate, not pus • Tissue easily dissected • Biopsy IDSA Guidelines. Stevens D et al. Clin Infect Dis 2005;42:1379-406

  42. Necrotizing Infections-Therapeutic approach • Surgical debridement/excision • Antimicrobial therapy • Directed initially against mixed aerobic/anaerobic flora • Ampicillin/sulbactam or Piperacillin/tazobactam PLUS clindamycin (theoretically to inhibit protein synthesis and supress bacterial toxin) PLUS ciprofloxacin; • Other regimens: imipenem, meropenem, ertapenem, clindamycin PLUS aminoglycoside or fluoroquinolone • Recommendation to use IVIG cannot be made with certainty • (Kaul et al. Clin Infect Dis 1999; Norrby-Teglund et al. Curr Rrep Inf Dis, 2001: Low et al, ICAAC 2003) DSA Guidelines. Stevens D et al. Clin Infect Dis 2005;42:1379-406

  43. Bacterial SST Infections • General approach to therapy • Surgical I&D, debridement, excision • Antimicrobial therapy • Directed against likely pathogens • Common organisms • Specific pathogens based on epidemiology • Emerging antimicrobial resistance • Community-onset MRSA; macrolide Res S pyogenes • Health0care associated pathogens

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