Cellulitis and Decubitus Ulcers

• The lecture covers cellulitis and decubitus ulcers (pressure sores).
• The lecture is part of the Infectious Diseases II course, MIC6640, Microbiology Division.

Cellulitis

• Cellulitis is an acute spreading infection of the dermis and subcutaneous tissues.
• The prevalence of cellulitis is unknown.
• There is no gender or race predilection for cellulitis.
• There are no age limits for cellulitis.
• Periorbital cellulitis must be treated in a hospital setting.

Pathogenesis of Cellulitis

• Cellulitis can be caused by the invasion of disrupted skin by microorganisms from trauma or surgery.
• Metastatic seeding can cause cellulitis, but it is rare, though it has the capacity to spread.
• Underlying osteomyelitis and foreign bodies like IV lines or orthopedic pins can cause cellulitis.

Cellulitis: Etiology

• In immunocompetent patients, Streptococci and Staph. aureus (frequently MRSA) are common etiologic agents of cellulitis.
• In immunocompromised patients, GNR, Anaerobes, and Fungi are common etiologic agents of cellulitis.
• Post saphenectomy can result in cellulitis from Streptococci.
  • Saphenectomy is defined as the surgical excision of the saphenous vein.
• Subcutaneous injection of illegal drugs can cause cellulitis, as in immunocompromised patients.
• Fresh water exposure can cause cellulitis from Aeromonas hydrophila.
• Sea water exposure can cause cellulitis from Vibrio species.
• Clostridia and B. fragilis are common etiologic agents of cellulitis related to the GI or GU Tract.
• S. aureus are common etiologic agents of cellulitis resulting from nasal carriage, IVDA, and Job's syndrome, which results in high levels of IgE.
• Orthopedic surgery patients are screened for Staph aureus colonization and are treated if colonized.

Cellulitis: Clinical Manifestations

• The incubation period for cellulitis is several days and organism-dependent.
• Local signs and symptoms of cellulitis include pain, tenderness, erythema, edema, local temperature increase, and lymphadenopathy.
• Systemic signs and symptoms include fever, malaise, and hypotension.

Cellulitis: Predisposition

• Serious spread of cellulitis results from immunodeficiency, diabetes mellitus, peripheral vascular insufficiency, and chicken pox.
• Recurrence of cellulitis results from chronic lymphedema, radiation, and peripheral vascular insufficiency.

Cellulitis: Complications

• Cellulitis can result in abscess, gangrene, osteomyelitis, necrotizing fasciitis, and bacteremia and sepsis.
• Gangrene resulting from cellulitis presents in patients with peripheral vascular disease.
• Osteomyelitis resulting from cellulitis is a common complication that requires surgical excision.

Abscess

• An abscess results from an inflammatory response that forms a cavity, where the capsule contains the infection preventing it from spreading.
• An abscess presents as a swollen area from an accumulation of pus and tenderness.

Gangrene

• Gangrene is the death of body tissue due to a lack of blood flow or bacterial infection.
• Gangrene is common in extremities.
• The skin will discolor, resulting in colors like pale, purple, and/or black.
• Gangrene can result in septic shock.

Osteomyelitis

• Osteomyelitis is an infection of bone.
• It spreads through blood or nearby tissue from trauma.
• Presents as swelling, warmness, tenderness over area of infection.
• A bone biopsy is the gold standard for diagnosis, but MRI is a second line method.
• Treatment requires 42 days of antibiotics.

Necrotizing fasciitis

• Rapidly progressive inflammatory infection of fascia.
• Necrosis of subcutaneous tissue.
• Can be polymicrobial or streptococcal.
• Clostridial myonecrosis involves clostridium perfringes, as well as deeper muscle infections that require the patient to be operated on.
• It is difficult to identify in early stages.

Bacteremia-Sepsis

• Bacteremia and sepsis is the presence of bacteria in blood (SIRS) in the presence of infection.
• Two or more of these criteria must be met:
  • Temp >38°C or <36°C
  • HR >90/min
  • RR >20/min
  • WBC >12,000 cells and/or Immature cells >10%.

Cellulitis Associated with Chronic Lymphedema

• Cellulitis is associated with chronic lymphedema from events like pelvic surgery, radiation, neoplasia, lower extremities, vulva, and inguinal area
• Is most commonly caused by Streptococci.
• It is refractory to treatment and recurrent.

Cellulitis Complicating Varicella

• Cellulitis characterized by erythema surrounding the vesicles, and results in deaths.
• A complication of untreated cellulitis can lead to severe disfiguring gangrene, requiring skin grafting, which happens with a patient scratches the affected area further infecting themselves.

Aeromonas hydrophila Cellulitis

• Aeromonas hydrophila cellulitis is the result of contact with fresh water.
• Can also occur through contaminated food and leeches (Hirudo medicinalis).

Erysipelothrix rhusiopathiae

• Is known as shrimp pickers' disease or crab poisoning
• Results in an acute infection of hand or fingers, characterized by mild aspect and severe pain.
• Self-limiting disease.

Cellulitis by Vibrio vulnificus

• Can result in Chronic Liver Disease (CLD), alcoholism, hemochromatosis, hemolytic anemia, HIV, DM, malignancy, etc.
• Iron and phagocytic defects
• Results from the consumption of oysters and shrimps.
• Fulminant illness with shock and high mortality (~90%)

Cellulitis: Differential Diagnosis

• Must differentiate from erysipelas, spider bite, acute gout, panniculitis, osteomyelitis, foreign body reaction, and necrotizing fasciitis.
• Erysipela vs Cellulitis: Erysipelas has a higher lymphatic component and raised borders, and takes longer to recover (more days of antibiotics).
• Spider bite: similar to community-acquired MRSA infection.
• Acute osteomyelitis and Foreign body: common denominator = lack of response to usual therapy for cellulitis.
• "Many times we don't know the exact origin of the infection," concerning necrotizing fasciitis.
  • High fever, intensive pain, toxicity; rapid deterioration.
  • Leukocytosis with shift to the left.
  • Most common: Streptococci and anaerobes.
  • Usually a clinical diagnosis.
  • Antibiotic and surgery required.
  • CT scan with contrast lets doctors know how deep the necrotizing fasciitis is.

Management of Cellulitis

• Goals: Eradicate infection and prevent complications.
• General measures: Bed rest, elevated limb, cool sterile saline compresses, analgesics.
• Medication: Antibiotics.

Decubitus Ulcers or Pressure Sores

• Decubitus ulcers are also known as pressure sores.
• Anatomic location: Hips and buttocks = 65%, Lower extremities = 25%, Remaining = 10%.

Pressure sores Pathogenesis

• Pathogenesis: prolonged pressure, impaired mobility, muscle atrophy, spasticity, sensory loss, trauma, malnutrition, and vascular disease.
• Pathophysiology: compression of tissues, microcirculatory occlusion, ischemia, inflammation, tissue anoxia, cell necrosis, and ulceration.

Development of pressure ulcer

• When pressure is applied, an ulcer forms in the soft tissue over a bony prominence.
• When the pressure is released, the skin heals, but underlying residual tissue damage remains.
• The newly expanded damage zone spreads out well beyond the original pressure point, when pressure is reapplied.
• Repeated pressure can cause a Grade ulcer, an open sore and necrosis down to the fascial level
• Can lead to osteomyelitis

Pressure Ulcers: Multidisciplinary Approach

• Reduce or eliminate the cause.
• Specialized support surfaces (<30 mm Hg)
• Turning and repositioning
• Keep the skin area clean
• Debridement and antibiotics
• Dressings (Stages II to IV)
• Nutritional status
• Contractures and spasticity

Pressure Sores: Management

• Do not forget:
  • Assessment of vascular supply
  • R/O = rule out osteomyelitis.

Malignant Degeneration of Pressure Sores

• Marjolin ulcer results in squamous cell carcinoma.

Abbreviations

• B/C = Blood cultures
• BUN = Blood urea nitrogen
• CLD = Chronic liver disease
• CT scan = Computerized tomography
• DM = Diabetes mellitus
• GABH = GroupA beta-hemolytic
• GIT= Gastrointestinal tract
• GNR = Gram-negative rods
• GU = Genitourinary
• HIV = Human immunodeficiency virus
• ICU = Intensive care unit
• ID = Infectious diseases
• IVDA = Intravenous drug abuse
• MRSA = Methicillin-resistant Staphylococcus aureus
• ORTHO = Orthopedic
• S/C = Subcutaneous
• Spps. = Species