1. Skin & Soft Tissue Infections
And Management of Animal Bites David H. Spach, MD Professor of Medicine Division of Infectious Diseases University of Washington, Seattle 1

2. Case History
Which of the following is true regarding impetigo? Penicillin is the optimal oral therapy 2. Group A Streptococcus alone causes more than 90% of cases 3. Amoxacillin is the optimal oral therapy 4. If localized, Mupirocin is an effective therapy 1

3. Impetigo (Pyoderma)
Cause - Staphylococcus aureus & Streptococcus pyogenes
Risk factors - Economically disadvantaged - Young children
Clinical Manifestations - Typically located on face and extremities - Vesicles  Pustules  Honey-colored crusts
From: Bisno AL, Stevens DL. N Engl J Med 1996;334:240-6. 1

4. IDSA 2014 SSTI Guidelines Treatment of Impetigo
Topical (for limited number of lesions): 7-day Rx - Mupirocin ointment bid x 7d - Retapamulin ointment x 7d
Oral: 7-day Rx - Dicloxacillin - Cephalexin - Erythromycin - Clindamycin - Amoxicillin-CA
Source: Stevens DL, et al. Clin Infect Dis. 2014;59:e10-52. 1

5. Skin Lesions 1

6. IDSA 2014 SSTI Guidelines Treatment of Ecthyma
Empiric Therapy - Cephalexin x 7d - Dicloxacillin x 7d
Suspected or Confirmed MRSA - Doxycycline - Clindamycin - TMP-SMX
Source: Stevens DL, et al. Clin Infect Dis. 2014;59:e10-52. 1

7. Case History: Skin & Soft Tissue1

8. Cellulitis
Cause - Common: Streptococcus sp.& Staphylococcus aureus - Less common: H. influenzae, S. pneumoniae, gram- bacilli
Risk Factors - Local trauma, abrasion, or skin lesion - Impaired lymphatic drainage of extremity
Clinical Manifestations - Typically located on extremities - Local (tenderness, erythema, & warmth), fever, chills, leukocytosis
From: Bisno AL, Stevens DL. N Engl J Med 1996;334: Sachs MK. Arch Dermatol 1991;127:493-6. 1

9. IDSA 2014 SSTI Guidelines Treatment of Cellulitis
Oral Therapy - Cephalexin - Penicillin
Intravenous Therapy - Penicillin - Clindamycin - Nafcillin - Cephazolin
Source: Stevens DL, et al. Clin Infect Dis. 2014;59:e10-52. 1

10. Case History: Skin & Soft Tissue
From: Bisno AL, Stevens DL. N Engl J Med 1996;334:240-6. 1

11. Erysipelas
Cause - Common: Streptococcus pyogenes (Group A) - Less common: Groups G, C, and B streptococci, S. aureus
Risk factors - Local trauma, abrasions, impaired lymphatic drainage
Clinical Manifestations - Superficial (raised) cellulitis with sharply demarcated border - Involvement of lower extremities more common than face - Blood cultures positive in only 5%
From: Chartier C et al. Int J Dermatol 1990;29: Bisno AL, Stevens DL. N Engl J Med 1996;334:240-6. 1

12. Hand Cellulitis 1

13. Case History
A 62-year-old man is admitted to the hospital with cellulitis. Four hours after admission he develops severe hypotension, increased creatinine, and a rapidly advancing cellulitis. 1

14. Case History
A 56-year-old man with diabetes undergoes bone marrow transplantation and has neutropenia. He develops a painful skin lesion on his right 5th toe. 1

15. Necrotizing Skin & Soft Tissue Infections Diagnostic Clues
Bullous lesions
Dark discoloration (blue/purple/grey)
Subcutaneous gas
Painful area that becomes anesthetic
Systemic toxicity
Rapidly advancing lesion 1

16. IDSA 2014 SSTI Guidelines Treatment of Necrotizing Fasciitis
Empiric Therapy Vancomycin or Linezolid Piperacillin-tazobactam or Carbapenem or Ceftriaxone + Metronidazole
Confirmed Group A Streptococcus - Clindamycin + Penicillin
Source: Stevens DL, et al. Clin Infect Dis. 2014;59:e10-52. 1

17. Case History: Skin & Soft Tissue
A 38-year-old man presents with fever and an abscess on his right arm. The lesion is very firm and is surrounded by erythema.
What would you recommend - Do you need to I & D? - Should you obtain cultures? - Do you need antibiotics? 1

18. MRSA Soft Tissue Infection1

19. MRSA Soft Tissue Infection1

20. This slide plots historic data from the National Nosocomial Infections Surveillance –or NNIS-system. The prevalenceo – or percent of S. aureus Nosocmial infections caused by methicillin-resistant S. areus is plotted over the past decade. These data are compiled from several of the NNIS reporting components, and in 1995, these data were extrapolated to the U.S. population, estimating that about 207 thousand S. aureus NI occurred annualy in the US—of which 70,000 were MRSA
Two additional points should be made regarding these data.
First, it is clear that the MRSA prevelance has continued to increase in the ICU setting, passing 50% in Several new approaches to reducing MRSA among ICU patients have been developed and tested—and you will hear from Others today on these initatives.
Second, as fewer hospitals reported sufficient data in the non-ICU areas in the past 10 years, making national estimates after 2000 became unreliable. Therefore, last year we partnered with NCHS to make national estimates using alternative data sources…….

21. Structure of Gram-Positive Bacteria
Penicillin Binding Proteins
DNA
Cell Wall
Cell Membrane 1

22. Beta-Lactams: Mechanism of Action
Penicillin Binding Proteins
Beta-Lactam
Transpeptidation Carboxypeptidation
DNA
Cell Wall
Cell Membrane 1

23. Methicillin-Susceptible Staphylococcus aureus
Beta-Lactam
Cell Wall Synthesis
DNA
Cell Membrane
Cell Wall
Penicillin Binding Proteins 1

24. Penicillin Binding Proteins
Staphylococcus aureus: Methicillin Resistance
Penicillin Binding Proteins
Nafcillin
mecA
PBP 2a
DNA
Cell Wall
Cell Membrane 1

25. Free Access
Source: Liu C, et al. Clin Infect Dis. 2011:52:1-38. 1

26. 2010 IDSA Practice Guidelines Therapy for CA-MRSA Skin & Soft Tissue Infection
Simple Abscess or Boil - Incision and Drainage
“For simple abscesses or boils, incision and drainage alone is likely adequate, but additional data are needed to further define the role of antibiotics, if any, in this setting.”
Source: Liu C, et al. Clin Infect Dis. 2011:52:1-38. 1

27. 2010 IDSA Practice Guidelines Therapy for CA-MRSA Skin & Soft Tissue Infection
Simple Abscess or Boil - Incision and Drainage
Complicated Abscess - Incision and drainage + antimicrobial therapy
Source: Liu C, et al. Clin Infect Dis. 2011:52:1-38. 1

28. 2010 IDSA Practice Guidelines Therapy for CA-MRSA Skin & Soft Tissue Infection
Complicated Abscess - Severe or extensive disease or rapid progression of cellulitis - Signs and symptoms of systemic illness - Associated comorbidities or immunosuppression - Extremes of age - Abscess in area difficult to drain (eg, face, hand, genitalia) - Associated septic phlebitis - Lack of response to incision and drainage alone
Source: Liu C, et al. Clin Infect Dis. 2011:52:1-38. 1

29. 2010 IDSA Practice Guidelines Therapy for CA-MRSA Skin & Soft Tissue Infection
Empiric Therapy for Out-Patient Management - TMP-SMX: 1-2 DS tabs PO BID - Clindamycin: mg PO TID - Doxycycline: 100 mg PO BID - Minocycline: 200 mg x1, then 100 mg PO BID - Linezolid: 600 mg PO BID
If Also Covering for Group A Streptococcus - TMP-SMX + Amoxicillin: 500 mg PO TID - Clindamycin - Doxycycline/Minocycline + Amoxicillin: 500 mg PO TID - Linezolid
Source: Liu C, et al. Clin Infect Dis. 2011:52:1-38. 1

30. Case History: Skin & Soft Tissue
This rash began about 5 days after a skiing trip in Canada. The rash itches. The patient is afebrile and otherwise doing well. In exam, it appears the hair follicles are involved.
What do you think is going on? 1

31. Case History: Skin & Soft Tissue
A 28-year-old man presents with a 3-day history of sinusitis symptoms and a 12-hour history of right eye swelling. He has a temperature of 38.5°C, eyelid edema, and eyelid erythema. He can not spontaneously open his right eyelid, but his vision and extra-ocular movements are intact. The most likely diagnosis is: 1. Blepharitis 2. Varicella-Zoster infection 3. Preseptal (periorbital) cellulitis 4. Postseptal (orbital) cellulitis 1

32. Case History: Skin & Soft Tissue
A 33-year-old man cut his hand on a piece of broken glass while cleaning out an aquarium. Several weeks later he noted a painful, draining nodule on his hand. He now has several more nodules proximal to the first nodule. The most likely diagnosis is: Mycobacterium marinum 2. Sporotrichosis 3. Aeromonas hydrophilia 4. Pseudomonas aeruginosa 1

33. Nodular Lymphangitis Mycobacterium marinum Sporotrichosis
Cutaneous Nocardia 1

34. Case History
A 28-year-old man presented to clinic with a 16 cm erythematous, annular skin lesion on his right flank and flu-like symptoms. He spent the past 30 days hiking in the mountains.
The most appropriate course of action is: Reassure and don’t give antibiotics 2. Draw serology and treat if positive 3. Give PO Doxycycline for days 4. Give IV Ceftriaxone for days 1

35. Important North American Ticks
Ixodes Female (Adult)
Ixodes Male (Adult)
Ixodes Nymph
Amblyomma Female (Adult)
Dermacentor Female (Adult)
Ornithodoros (Adult)
From: Spach DH, et al. N Engl J Med 1993;329: 1

36. Ixodes scapularis Blacklegged Tick
Source: CDC Control and Prevention. 1

37. Ixodes pacificus Western Blacklegged Tick
Source: CDC Control and Prevention. 1

38. Distribution of Tick Species in Washington State, 1989
Source: Washington Department of Health. 1

39. Distribution of Tick Species in Washington State, 1989
Source: Washington Department of Health. 1

40. Erythema Migrans Rash From: Steere AC. N Engl J Med. 2001;345:115-25.

41. Lyme Disease: General Approach to Treatment
Early Disease (Absence of serious Neurologic/Cardiac) - Doxycycline - Amoxicillin
Late Disease or Serious Neurologic/Cardiac Disease - Ceftriaxone 1

42. Case History: Animal Bite
A 33-year-old woman living in Washington State is bitten on her hand by her cat while trying to break up a fight between her cat and dog. One day later her wound is red and painful and she comes to the ER for evaluation. Which of the following is TRUE? 1. Her risk of getting rabies from this cat bite is about 2% 2. Cat bites become infected more often than dog bites 3. Bartonella is the most likely cause of the infection 4. Pseudomonas is the most likely cause of the infection 1

43. Microbiology of Infected Cat Bites
From: Talan DA, et al. NEJM 1999;340:85-92. 1

44. Case History: Question
A 29-year-old is bitten by a dog on his hand while trying to break up a dog fight between 2 pets. This took place in Seattle.
Which of the following is TRUE regarding dog bites and infection? 1. His risk of getting rabies from this dog bite is about 5% 2. Pseudomonas cani is a common pathogen 3. Optimal prophylaxis is Amoxicillin 4. Pasturella is one of the most commonly isolated organisms 1

45. Microbiology of Infected Dog Bites
From: Talan DA, et al. NEJM 1999;340:85-92. 1

46. Dog & Cat Bites Wound Infections: Therapy
Therapy (Oral) - Amoxicillin-CA x 7-14 days
Therapy (Intravenous - Ampicillin-sulbactam - Ertapenem
Therapy (Penicillin-Allergic) - Clindamycin plus Fluoroquinolone 1

47. Case History: Skin & Soft Tissue
This 36-year-old man is admitted to intensive care unit 3 days after suffering a dog bite on his right knee. He has a BP = 85/60, he has diffuse purpura, and lab studies that show evidence of DIC. Tragically, he died 6 hours after admission to the ICU.
Which organism most likely caused this infection? 1. Moraxella catarrhalis 2. Pasteurella canis 3. Capnocytophaga canimorus (DF-2) 4. Pseudomonas aeruginosa 1

48. Cat Scratch Disease: Bartonella henselae1

49. Cat Scratch Disease: Azithromycin Therapy
From: Bass JW et al. Pediatr Infect Dis 1998;17: 1

50. Questions? 1