Skin, Bone, and Joint Infections

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Skin, Bone, and Joint Infections

• Charles S. Bryan, M.D.
• November 26, 2007

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Overview of skin infections

• Pyodermas
• Secondary bacterial infections complicating
  pre-existing lesions of the skin
• Skin lesions in septicemias
• Infectious gangrene, gangrenous cellulitis, gas
  forming infections, and other surgical
  infections

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Overview of the pyodermas

• Impetigo
• Staphylococcal scalded skin syndrome
• Folliculitis, furuncles, and carbuncles
• Ecthyma
• Erysipelas and cellulitis
• Erythrasma

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Non-bullous impetigo

• Superficial (intraepidermal)
• Initially vesicular, then becomes crusted
• Unit lesion intraepidermal, unilocular
  vesicopustule
• Stuck-on honey-colored crust
• S. pyogenes (90) also S. aureus
• Mainly children highly communicable

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Ecthyma

• Begins in the epidermis (like impetigo), but
  penetrates down in to the dermis to form
  punched-out ulcers covered by greenish-yellow
  crusts and surrounded by raised violaceous
  margins
• Group A streptococci can cause as primary or
  secondary infection
• See also ecthyma gangrenosum (below)

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Bullous impetigo

• Mainly newborn and younger children
• About 10 of all cases of impetigo
• Caused by S. aureus of phage group II (usually
  type 71)
• Exfoliative toxins explain formation of bullae

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Staphylococcal scalded skin syndrome

• Younger children can cause epidemics in
  nurseries (pemphigus neonatorum or Ritters
  disease)
• A severe reaction to S. aureus strains producing
  exfoliative toxins
• Large, flaccid bullae rupture, causing same
  effect as a third-degree burn

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Folliculitis

• A pyoderma involving the hair follicles of the
  apocrine regions
• Small papules evolve into pustules
• S. aureus the usual cause
• Pseudomonas aeruginosa (pools whirlpools)
• Candida species in hospitalized patients
• Malassezia furfur (diabetes, steroids)

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Furuncles (boils) and furunculosis

• Usually arise from folliculitis
• S. aureus the usual pathogen
• Some persons have a tendency to develop multiple,
  recurrent furuncles (furunculosis) most are
  chronic nasal carriers of S. aureus but otherwise
  the predisposition is largely unexplained

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Carbuncles

• Similar to furuncles but larger, deeper, and more
  extensive
• Usually at nape of the neck, on the back, or on
  the thighs
• Usually due to S. aureus
• Can produce significant systemic symptoms

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Hidradenitis suppurativa

• Chronic infections of the apocrine glands in the
  axillae (hidradenitis suppurativa axillary),
  groin (hidradenitis suppurativa inguinalis), or
  perianal lesions
• Primary lesion probably non-infectious
• Usually refractory to antibiotic therapy

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Cellulitis

• An acute spreading infection involving the dermis
• Erysipelas is a type of cellulitis involving
  mainly the dermis other forms of cellulitis
  extend to the subcutaneous tissues
• Most cases are due to S. aureus and/or group A
  streptococci

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Erysipelas

• A dramatic, rapidly-spreading cellulitis nearly
  always caused by group A streptococci
• Lymphangitic streaks and tender regional
  lymphadenopathy
• Lower extremities in 80 of cases face in 5 to
  20 of cases
• Tends to recur after first episodes

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72 y.o. retired nurse

• CC swelling of left side of face X 1 day
• One day PTA Sore throat, then swelling of left
  side of face Dx cellulitis, Rx antibiotics
• Day of admission pain, left side of face with
  further swelling. Fever not a complaint.
• PMH atrial fibrillation syncopal disorder
  hypertension type I allergy to PCN remote
  history of breast cancer (1991) meds digoxin,
  Lopressor, warfarin, Lasix, ASA

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On admission

• NAD uncomfortable
• Temp. 96.9, BP 97/54 SP02 98
• WBC 10.2K BUN 19, creatinine 1.8 mg/dL
• CT scan diffuse swelling, no deep inflammatory
  process, cavernous sinus area OK
• Rx vancomycin, aztreonam, metronidazole (per
  2007 Sanford guide)

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Day 2

• BP dropped to 60 systolic atrial fibrillation
  with rapid ventricular response
• Transferred to ICU BP quickly restored
  increased neck swelling (sublingual/submandibular)
  
• WBC 11.9 K blood cultures sterile
• Tracheostomy done aspirates of
  submandibular/sublingual spaces no indication of
  abscess

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Day 3

• Eye culture from admission group A streptococcus
  (preliminary)
• Temp. 99.4, BP 87-103/55-72, SP02 92-100
• WBC 11.4K, platelets 114K
• Dx Probable early streptococcal toxic shock
  syndrome
• Rx Clindamycin IVIG

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Subsequent course

• Day 4 Improved
• Day 5 Worse SP02 91-92 on ventilator WBC 18.7
  K, BUN 40, creatinine 1.1, anion gap 21 with
  lactic acid 3.5, AST 300, ALT 208, prothrombin
  time 45.6 seconds
• Day 6 Expired

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Unusual causes of cellulitis

• Aeromonas hydrophila wounds fresh water
• Vibrio species wounds salt water
• Erysipelothrix rhusiopathiae salt-water fish,
  meat, poultry, hides
• H. influenzae young children
• Cryptococcus neoformans immunocompromised

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Erythrasma

• A common superficial infection
• Slowly-spreading, reddish-brown, finely-wrinkled
  macule, often quite pruritic
• Usually in the genitocrural area, especially men
  who are often obese or who have diabetes
• Corynebacterium minutissimum coral-red
  fluorescence under Woods light

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Chronic superficial skin ulcers

• Decubitus ulcers
• Diabetic foot ulcers
• Venous stasis ulcers
• Classically these become infected with a
  combination of aerobic and anaerobic pathogens
  extensive skin and bone involvement can occur

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Skin infections in immunocompromised patients

• Can occur after minor trauma
• Can be due to virulent pathogens or
  opportunistic pathogens
• Examples include the less-pathogenic fungi (e.g.,
  Alternaria, Trichophyton, Penicillium),
  mycobacteria, and even algae

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Myositis

• Pyomyositis uncommon usually due to S. aureus
  (95) especially seen in tropics
• Clostridial myonecrosis (true gas gangrene)
• Nonclostridial (crepitant) myositis Includes
  anaerobic infections synergistic (mixed)
  infections infected vascular gangrene Aeromonas
  hydrophila infection

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Septic arthritis overview

• Incidence 2 to 10 per 100,000 in general
  population but 30 to 70 per 100,000 in patients
  with rheumatoid arthritis and/or joint prostheses
• Irreversible loss of joint function develops in
  25 to 50 of patients
• Mortality 5 to 15

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Septic arthritis overview (2)

• Usually hematogenous
• Can result from wounds or from intra-articular
  injection of mediations
• Predisposing factors trauma endocrine notably
  with gonococcal arthritis underlying joint
  disease

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Acute bacterial arthritis

• Usually monoarticular (90)
• Knee most common (50) then hip
• Children also ankle and elbow
• Adults also shoulder, sacroiliac joints,
  sternoclavicular joints

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Acute bacterial arthritis (2)

• Children under 2 Haemophilus influenzae
• Sexually-active adults under 30 N. gonorrhoeae
• S. aureus important in all age groups most
  common agent in adults 30 usual cause (80)
  with rheumatoid arthritis
• others Enterobacteriaceae, Pseudomonas sp., S.
  pneumoniae

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Chronic monoarticular arthritis with
granulomatous histology

• Mycobacteria
• Nocardia
• Sporotrichosis
• Other fungi
• Brucellosis

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Lyme disease and arthritis

• Months after the onset of late infection, about
  60 of patients who have received no antibiotics
  develop frank arthritis, typically intermittent
  attacks of oligoarticular arthritis in large
  joints.
• A high percentage of these patients have the
  class II MHA complex allele HLA-DR4

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Viral arthritis

• Rubella joint involvement is usually
  polyarticular
• Mumps polyarticular arthritis
• Hepatitis B symmetric arthritis related to
  immune complexes
• Parvovirus B19 in adults pauciarticular
  arthritis with rash
• HIV disease

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Whats your diagnosis?
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Post-infectious arthritis syndrome

• Reactive arthritis
• Apparently due to immune complexes
• Especially common in persons with
  histocompatibility antigen HLA-B27
• Tends to occur after gastrointestinal symptoms
  with Shigella, Salmonella, Campylobacter, and
  Yersinia

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Osteomyelitis (overview)

• A difficult-to-treat infection characterized by
  the progressive inflammatory destruction and new
  apposition of bone
• Three clinical types hematogenous osteomyelitis
  osteomyelitis secondary to a contiguous focus of
  infection and osteomyelitis secondary to
  vascular insufficiency

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Osteomyelitis pathogenesis

• Normal bone resists infection
• Certain pathogens, notably S. aureus, adhere to
  bone by expressing receptors (adhesins) for
  components of bone matrix and cartilage.
• S. aureus can survive intracelluarly in
  osteoblasts

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Osteomyelitis pathogenesis (2)

• Normal bone remodeling requires coordinated
  interplay of osteoblasts and osteoclasts
• Cytokines (e.g., IL-1, IL-6, TNF) are potent
  osteolytic factors
• Arachidonic acid metabolites (e.g., PGE2 decrease
  the amount of inoculum need to cause infection

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Osteomyelitis pathogenesis (3)

• Pus spreads through vascular channels, raising
  intraosseous pressure and impairing blood flow
• Ischemic necrosis causes separation of
  devascularized fragments (sequestra)
• Necrotic bone (recognized by absence of living
  osteocytes) is a hallmark of chronic osteomyelitis

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Osteomyelitis microbiology

• Salmonella or Streptococcus pneumoniae sickle
  cell disease
• Coagulase-negative staphylococci or
  Propionibacterium sp. foreign bodies
• S. aureus most common pathogen
• Enterobacteriaceae or Pseudomonas aeruginosa
  nosocomial infections

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Osteomyelitis microbiology (2)

• Pasteurella multocida animal bites
• Eikenella corrodens human bites
• Bartonella henselae HIV disease
• Aspergillus, Candida albicans, MAC
  immunocompromised patients
• M. tuberculosis, Brucella, Coxiella burnettii (Q
  fever), and fungi certain high-prevalence
  populations

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Hematogenous osteomyelitis

• Usually affects the metaphysis of growing bones
• The sharp loops formed by nutrient arteries as
  they approach the epiphyseal growth plates
  results in metaphyseal capillaries where blood
  flow is sluggish and phagocytic lining cells are
  absent (afferent loops) or functionally inactive
  (efferent loops)

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Hematogenous osteomyelitis (2)

• Most commonly occurs in children, prior to fusion
  of epiphyseal plates in growth ends of long bones
• In adults, especially over age 50, tends to occur
  in the spine (vertebral osteomyelitis--an
  important and difficult disease to recognize)

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Hematogenous osteomyelitis (3)

• S. aureus the most common pathogen. Often there
  is a history of preceding minor trauma, setting
  up a locus minoris resistentiae
• Other pathogens include streptococci (especially
  neonates), Salmonella species (especially in
  sickle cell disease) and Pseudomonas species (IV
  drug users)

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Vertebral osteomyelitis

• Nearly always represents hematogenous
  osteomyelitis
• Typically involves two adjacent vertebrae and the
  disk space between them
• Neck or back pain and fever are the main symptoms
• Physical exam localized spinous tenderness

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Osteomyelitis due to a contiguous focus of
infection

• Predispose trauma, surgery, bite wounds,
  puncture wounds
• Typical patient someone who has had undergone
  ORIF for fracture
• Often polymicrobial
• Associations Pseudomonas aeruginosa nail
  puncture Pasteurella multocida animal bites
  anaerobes trauma or decubitus ulcers

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Osteomyelitis associated with vascular
insufficiency

• Mainly polymicrobial osteomyelitis of the small
  bones of the feet in patients with advanced
  diabetes mellitus and sensory polyneuropathy
  (neuropathy
  --ulcers--bone penetration)
• On average, 6 bacterial species per case, evenly
  distributed among aerobes and anaerobes