septic arthritis inflammation of a joint caused by a bacterial infection

Septic arthritis

Inflammation

of a joint caused by

a bacterial infection

Septic arthritis is also called infectious arthritis

Septic arthritis is diagnosed by identifying

infected joint fluid

Epidemiology

Incidence:

General population 2-5/100,000/yr

Children 5.5 - 12/100,000/yr

RA 28 - 38/100,000/yr

Prosthetic joint 40 - 68/100,000/yr

Monoarticular (<20% more than one joint)

Large joints>small joints

Knee (>50%), ankle, wrist, hip, …

The most common joints to become infected are the knee

In infants under the age of three, septic arthritis usually affects the hip

Epidemiology:

Tow peaks in the age related incidence children < 5 years adult > 64 years> 75% of childhood SA previously healthy> 75% of adult onset SA predisposing factor

Etiology

Gonococcal

Non gonococcal

Gram-positive cocci (75-80%)

• Staphylococcus aureus (most common)

• Staphylococcus epidermidis

Immuncompromise, joint surgery

• β-Hemolytic Streptococci

• Streptococcus pneumoniae (polyarticular, bacteremia)

Hemophilia,Sickle cell disease

Older age, comorbidity

Microbiology :

Every bacterium has been reported to cause SA.

Staph. aureus 40-60%Streptococcus 9.5-28%S. pneumoniae 5.5-9.7%gram negative bacilli 9-19%Anaerobes 1.2-6%

Etiology Gram-negative bacilli (15-20%)

• E-coli• Pseudomonas IV drug abuse, immuncompromise Older age, Comorbidity, UTI

• Salmonella• Proteus SLE

Anaerobes (5-7%) Trauma, joint surgery

Clinical presentation:

Acute onset of pain and swelling in a single joint.

The pain is typically severe and occurs at rest.Large joints (knee, hip, ankle, shoulder)Fever 60-80% (mild)Chills (unusual)Warmth, tenderness, effusion and limited

active and passive range of motion

Polyarticular septic arthritis:

10-15%Two or more jointsS. aureus is the most common pathogenMore common in s. pneumoniae (36%)Streptococci, H-influenza, salmonella,

gonorrhoeae, anaerobesMany have comorbidity (RA, IVDA)Mortality

Risk factors :Prosthetic jointUnderlying joint diseases ( RA , OA )Age > 80 yearsRecent joint surgery Previous SADiabetes mellitus, hemodialysis, advanced hepatic

disease, malignancy, hemophilia, sickle cell disease, hypogammaglobulinemia, IV drug abuse, AIDS

Low social economic status Skin infection

Pathogenesis

Bacterial colonization

host immune response

Joint damage

Pathogenesis

Hematogenous seeding• Most common• Abundant vascular supply of synovium and lack of a limiting basement

membrane

Direct inoculation• Trauma • Joint surgery• Arthroscopy (<0.5%)• Joint aspiration and injection (0.0002%)• Osteomyelitis, cellulitis, or septic bursitis

Source of infection :

Hematogenous seeding (bacteremia): skin, lung, urinary tract, oral cavity, IV catheter Direct inoculation : joint aspiration and injection (0.0002 %) arthroscopic surgery (0.5 %)Spread from adjacent soft tissue infection or

osteomyelitis (hip and shoulder)

Pathogenesis

Microbial factors:

virulence

Attach to host tissue within joint Evade host defenses

Host factors:

Immune response Opsonization Phagocytosis cytokines

Clinical manifestations

Monoarticular, knee

• Febrile

• Acute onset of pain and swelling

• Warmth and tenderness, joint effusion, redness and limited

active and passive ROM

How is it diagnosed?

Diagnosis

History

PH/E

Arthrocentesis

Imaging

Diagnosis

Arthrocentesis Normal synovial fluid:

• Small amount

• Clear

• Highly viscous

• Few WBCs (<200)

• Protein concentration is one third of plasma

• Glucose concentration is similar to plasma

Diagnosis

Septic joint:

• Purulent

• Decreased viscosity

1. WBC > 50,000/mm³, PMN predominance

• Glucose less than half the serum glucose

The normal joint fluid is sterile and, if removed and cultured in the laboratory, no microbes will be detected.

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Organisms in septic arthritis• Gram -positive cocci

– S. aureus – S. pyogenes– S. pneumoniae – S. viridans group

• Gram-negative cocci– N. gonorrhoeae and meningitidis – H. influenzae

• Gram-negative bacilli– E. coli– Salmonella – Pseudomonas species

• Mycobacteria and Fungi

Diagnosis

Definite diagnosis: Gram-stained smear and culture of synovial fluid

• Smear: Gram-positive cocci: 50% - 75% Gram-negative bacilli: <50%

• Culture: 70% - 90%

• Blood culture: 40% - 50%

• Extraarticular site of infection

Diagnosis

Imaging: Plain radiographs

• Early stages: normal, soft tissue swelling

• Advanced infection: periosteal reaction, marginal or central erosions, destruction of subchondral bone, Bony ankylosis

• Baseline films should be obtained to look for evidence of other

disease and osteomyelitis

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Staphylococcal arthritis: wrists (radiograph)

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Septic arthritis: early and late changes, hip (radiographs)

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Septic arthritis: sternoclavicular joint (technetium radioisotope scan)

Differential diagnosis

Crystal induced arthritis

RA

Reactive arthritis

Trauma

………………..

If septic arthritis is left untreated

Treatment: septic arthritis is suspected

blood and synovial fluid sample

empiric parenteral antibiotics based on gram stain

joint drainage

adjust antibiotics based on culture and sensitivity results

Treatment

Immediate treatment after clinical

evaluation and cultures

Appropriate antibiotics and adequate

drainage

Initial treatment is IV

Treatment

Gram-positive cocci• MSSA Nafcillin/Oxacillin 2gr IV q4h • MRSA Vancomycin

1gr IV q12h

Gram-negative bacilli Ceftriaxone/Cefotaxime 2gr IV q24h/ 2gr IV q8h

• Pseudomonas Piperacillin/Ceftazidime + AG

3gr IV q6h/ 2gr IVq8h

Treatment

No organism• Healthy, sexually active patient with community-acquired septic

arthritis

Ceftriaxone or Cefotaxime

• Elderly debilitated patient

Antistaphylococcal + Antipseudomonal

+ AG

Polymicrobial

Nafcillin/oxacillin + ceftriaxone/cefotaxime

Prognosis

Patients receiving immunosuppressive therapy

Serious underlying comorbidities (liver, kidney, or heart diseases)

Juxta-articular osteomyelitis

Disability: 25-50%

Mortality: 5-20%

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Septic olecranon bursa

There are more than 150 bursae in the human body.

Superficial

Deep

Gonococcal arthritis

Neisseria gonorrhea

Clinical presentation:

• Disseminated gonococcal infection (DGI)

• Gonococcal septic arthritis

Most common cause of acute monoarthritis in sexually

active healthy young adults

DGI is more common in women than men (3/1)

Gonococcal arthritis

Clinical features

DGI

• Women/men: 3/1

• Intrauterine devices, menstruation, pregnancy, and pelvic operation

• Fever, shaking chills, skin lesions (vesiculopustular, hemmorhagic),

tenosynovitis (wrist, fingers, ankle, and toes), polyarthralgias, and arthritis

septic arthritis

• knee, wrist, ankle, or more than one joint

Gonococcal arthritis Diagnosis

DGI:

• Skin lesion culture: negative • SF culture: often negative• Blood culture: 50% positive• Culture from genital, rectal, and pharyngeal sites

Septic arthritis:

• SF culture: 50% positive• Blood culture: often negative

DNA-PCR

Gonococcal arthritis

Treatment

DGI:

• Ceftriaxone/cefotaxime 7-10 days

• Doxycycline

Septic arthritis:

• Ceftriaxone/cefotaxime 7-14 days

• drainage

Prosthetic joints infection

Epidemiology

• Knee: 1-2%

• Hip: 0.5-1%

• Shoulder: <1%

Prosthetic joints infection

Clinical manifestations Depend on the timing of infection:

Early (<3 m)

• Acquired during implantation

• Virulent pathogens such as S. aureus or gram-negative bacilli

• Joint pain, and effusion, wound drainage, fever,

implant site erythema, induration or edema, sinus tract

Prosthetic joints infection

Delayed (3 - 24 m)

• Acquired during implantation

• Less virulent pathogens such as S. epidermidis, P. acnes

• Persistent joint pain, with or without implant loosening, fever< 50% and

leukocytosis<10

Late (>24 m)

• Hematogenous

• S. aureus

• Joint pain, tenderness and swelling, fever, leukocytosis

Prosthetic joints infection

Treatment

Medical and surgical

• Organisms within biofilms are resistant to antibiotics: