TOC | Rheumatology

Septic/Bacterial Arthritis

Characteristics of Septic Arthritis  

1. Most rapidly destructive

2. Gonococcal and Meningococcal

• Reactive Arthritis - may be weeks or months post-infection
• Disseminated Infection - organisms may be cultured from joint
• May resemble systemic vasculitis [2]

3. Non-Gonococcal

• Immunocompromised Host (mainly HIV) - atypical organisms
• Normal Host - streptococci and staphylococci
• Lyme Arthritis See outline "Lyme Disease"

4. Predisposing Factors for Non-Gonococcal Arthritis

• Rheumatoid Arthritis, Crystal Induced Arthritis, Severe Osteoarthritis, Trauma, Charcot Joint, Sickle Cell Disease, Intravenous Drug Abuse (often with endocarditis), Hemarthrosis (especially in hemophiliacs), Prosthetic Joint

Joints Involved

• Knee 55%, Hip 11%, Ankle 8%, Shoulder 8%, Wrist 7%, Elbow 6%, >1 Joint 12%

Organisms (non-gonococcal)

1. S. aureus ~50%
2. Group A Strep ~15%
3. Gram Negative Rods ~15%
4. S. pneumoniae ~ 5%
5. Polymicrobial ~ 5%
6. Mycobacterium [3]
7. Fungi (usually in immunosuppressed hosts)

Diagnosis

1.In nearly all cases, an acute monoarthritis should be aspirated to rule out infection

• a.Rapid Gram-stain and culture should be performed
• b.If neutrophils predominate with >50K/µL leukocyte counts, consider empiric antibiotics

2.Culture

• a.~100% sensitivity for non-gonococcal
• b.~30% sensitive for GC
• c.Atypical organisms should be sought including fungi, mycobacteria

3.Gram stain

• a.~75% sensitivity for gram positive cocci
• b.~50% sensitivity for gram negative rods

4.Leukocyte Joint Fluid Count

• a.Usually >50K/µL with >80% neutrophils
• b.Rheumatoid Arthritis and Crystal Disease occassionally have such high cell counts

5.Lactate Dehydrogenase - low or normal usually rules out bacterial disease

E. Differential Diagnosis

1. Mycobacterial or fungal arthritis - usually insidious (slow) onset
2. Viral arthritis - usually with rash, usually polyarthritis
3. HIV Infection - often with reactive arthritis, sterile acute synovitis
4. Hemearthrosis - especially with trauma, coagulopathy, blood-thinners
5. Lyme Disease
6. Reactive Arthritis - compenents of Reiter's syndrome
7. Rheumatoid Arthritis
8. Crystal Disease - gout, pseudogout

Treatment

1.Depends on organism and host

2.Antibiotics

• a.Usually begin with oxacillin (nafcillin) or vancomycin
• b.Add gentamicin initially until culture results back
• c.Consider broader bacterial and atypical coverage in immunocompromised hosts
• d.Ceftriaxone or Cefotaxime for gonococcus or meningococcus

3.Open vs. closed joint aspiration

4.In general, joint should be drained daily until accumulation (nearly) ceases

5.Indications for surgery

• a.Continued accumulation of fluid
• b.Continued bacteremia
• c.Difficult to get-at joints (eg. hip, sternoclavicular)
• d.Prosthetic joints - usually requires removal of prosthesis
• e.Coexistant osteomyelitis
• f.Fungal or other atypical infection

6.NSAID Therapy can decrease pain and inflammation (better than acetaminophen)

Septic Bursitis

1.Most commonly occurs in olecranon or pre-patellar bursa

• a.Trauma is major risk factor
• b.Alcoholism
• c.Diabetes mellitus
• d.Typically occurs in middle-aged men involved in manual labor

2.Etiology of Bursitis

• a.Infectious agents - through breaks in skin
• b.Inflammatory Disease - rheumatoid arthritis, gout, pseudogout, spondylitis

3.Organisms

• a.S. aureus 80%
• b.Group A Streptococci (ß-hemolytic) ~5%
• c.Staphylococcus epidermidis ~5%
• d.Variety of other bacteria (gram positive and negative)
• e.Atypical bacteria, Fungi, algea

4.Symptoms of Septic Bursitis

• a.Bursal warmth ~100%
• b.Bursal tenderness ~100%
• c.Prebursal cellulitis ~80%
• d.Skin Lesion ~55%
• e.Fever ~40%

5.Laboratory Findings

• a.Bursal Fluid White Count usually ~50-150K/µL (>80% neutrophils)
• b.Gram Stain demonstrating organisms in ~20% of cases
• c.Bursal fluid glucose usually <35mg/dL

6.Associated Diseases

• a.Septic Arthritis and Osteomyelitis
• b.Toxic Shock Syndrome (usually staphylococcal)
• c.Polymicrobial Infection - especially in patients with chronic disease, diabetes
• d.Necrotizing Fasciitis

7.Treatment

• a.Intravenous antibiotics are almost always indicated
• b.Gram positive coverage usually sufficient except in immunocompromised host
• c.Broader spectrum coverage (eg. Unasyn®, Timentin®) recommended in complicated host
• d.Repeated drainage of bursal area (usually without irrigation) is required
• e.Failure of bursal cell counts to drop with treatment suggests surgical evaluation
• f.A minimum of 4-7 days intravenous antibiotics recommended, followed by oral therapy
• g.Total duration of therapy depends on response and comorbid conditions
• h.A minimum of 2 weeks total therpay is recommended

Outline Medicine on Physician Online 2000

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