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Rheum/Musculoskeletal/Derm Week 2 > Infectious Arthritis > Flashcards

Infectious Arthritis Flashcards

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1
Q

What is Native Acute Infectious Arthritis?

A

refers to infection of a joint (primarily bacterial but can be from anything really) that when is BACTERIAL in nature is considered a surgical emergency to due to the potential for rapid joint destruction and loss of function.

Note that infectious arthritis with a mycobacterial, fungal (other than candida), or viraletiology is usually more of a chronic and slowly progressive process

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2
Q

How common is infectious arthritis? How severe? Risk factors?

A

In a normal population this is very rare but risk increased in RHEUMATOID ARTHRITIS patients

Mortality can be up to 15% in a healthy population but can icnrease up to 50% in those with significant comorbidities and multiple joint involvement

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3
Q

If infectious arthritis is treated properly, will everything return to normal?

A

Not always- up to 50% report permanent decreased joint function/mobility after infection

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4
Q

What is the most common cause of infection in infectious arthritis?

A

•Usually hematogenously acquired during overt or occult bacteremia including that caused by endocarditis

NOTE: NORMAL, diseased, OR prosthetic joints are all susceptible but abnormal joint architecture increases the risk

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5
Q

Why are joints so susceptible to hematogenous deposition of bacteria?

A

Synovial membranes are very vascular and lack a basement membrane

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6
Q

What are some other ways bacteria can be introduced into joints?

A

–Direct inoculation of bacteria into the joint through surgery, trauma, bites, percutaneous puncture (nail, needle, etc)

–Contiguous spread from adjacent infected soft tissue or bone.

•Eg: small joints of foot become infected from a diabetic foot ulcer or infection.

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7
Q

What are the known risk factors to infectious/septic arthritis?

A
  • Preexisting abnormal joint architecture (most important). Eg: RA, osteoarthritis, gout
  • Advanced age
  • Diabetes mellitus
  • Previous joint surgery
  • IVDU
  • Endocarditis
  • Immunosuppression (steroids and TNF-a blockers common)

Up to 22% of patients with septic arthritis

will not have an identifiable risk factor

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8
Q

What is septic arthritis dependent on?

A

Adherence of organisms to and colonization of synovial membrane, bacterial proliferation in synovial fluid, and resultant synovial infection with host inflammatory response

–After entry into the joint, bacterial adherence is facilitated by vascular synovial membrane with increased adhesion factors

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9
Q

Why woudl joint disease/injury promote bacterial infection?

A

–If joint disease/injury is present this results in increased amount or exposure of host-derived extracellular matrix proteins such as fibronectin, collagen, elastin, hyaluronic acid which promote bacterial attachment

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10
Q

What is the most common cause of septic arthritis?

A

Staph aureus (especially in RA - up to 75%- and IVDUs)

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11
Q

MRSA is a common cause of septic arthritis in what patient populations?

A
  • elderly,
  • those with recent orthopedic surgery, and
  • those colonized with or previously infected with MRSA
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12
Q

Other frequent causes of septic arthritis?

A
  • Streptococcus (A, C, G)
  • S. pneumoniae
  • Coag neg staphylococcus
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13
Q

Group B strep is a common cause of septic arthritis in what patient?

A

–cause in neonates, diabetics, those with malignancies. Can cause polyarticular infection

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14
Q

Gram negative bacilli are a cause in 5-20% of patients with septic arthritis especially in certain, at-risk populations. What populations am I referring to?

A
  • neonates
  • elderly
  • IVDU
  • immunocompromised
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15
Q

What gram neg rod is likely to cause septic arthritis in IVDUs?

A

P. aeruginosa (also a big cause of iatrogenic septic arthritis after surgical procedures/intra-articular injections

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16
Q

What gram neg rod is likely to cause septic arthritis in young adults and those with MAC complex complement deficiencies?

A

Neisseria gonorrhea, Neisseria meningitidis respectively

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17
Q

What gram neg rod is likely to cause septic arthritis in immunocompromised (esp SCD and SLE)? Cat or dog bite? Unpasteurized milk?

A

Salmonella spp.

Cat or dog bite: Pasteurella multocida

Unpasteurized milk: Brucella (causes SI joint arthritis)

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18
Q

How does the arthritis of septic arthritis present?

A

•Mono-articular in 80-90% of cases, knee in approximately 50% of patients

–Other frequently involved joints: hip, shoulder, wrist, ankle

•Polyarticular bacterial arthritis seen in 10-20% of patients (RA, immunosuppression, prolonged or intense bacteremia; usually caused by S. aureus.)

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19
Q

Most common joint affected by septic arthritis in children?

A

hip

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20
Q

How does septic arthritis present?

A
  • Most present with intense pain and loss of function of one or more joints over 1-2 week period
  • Other symptoms: swelling, redness, increased warmth of joint
  • Fever and malaise common, however high fevers with shaking chills typically absent
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21
Q

Signs of septic arthritis?

A

you might see

  • Focal joint tenderness
  • Inflammation
  • Effusion
  • Limited ROM (active and passive) and results in considerable pain
  • Children with septic hip: hold hip in a flexed and externally rotated position, resist any ROM
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22
Q

What is this?

A

Sternoclavicular septic arthritis: uncommon except in IVDU

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23
Q

Septic arthritis

A

Right: Septic arthritis of 3rd metacarpophalangeal joint due to Pasteurella multocida after a cat bite

24
Q

How is septic arthritis treated?

A

•Diagnosis REQUIRES arthrocentesis of affected joint

–Historically synovial fluid leukocyte count (most of which are neutrophils) >50,000 cells has been used to diagnose septic joint

  • Lower WBC counts are regularly encountered and don’t exclude the diagnosis
  • >100,000 leukocytes: you can pretty much bet this is a septic joint
25
Q

Rules for treating septic arthritis

A

Fluid culture will be positive 80-90% of the time; gram stain positive in only 50% of cases

Get blood cultures: positive 25-75% of the time

Try to tap the joint and get blood cultures prior to antibiotics

Avoid puncturing skin visibly involved with cellulitis

26
Q

What is this?

A

Arrow shows bony erosion; also shows soft tissue swelling in septic arthritis

27
Q

What is this?

A

Pubic symphysis septic arthritis: widening of joint space, small cortical erosions Patient had had a prostatectomy 2 weeks earlier. Urine culture grew P. aeruginosa

28
Q

How to treat if a gram stain shows GPCs? GNRs?

A

GPCs: Vanco

GNRs:

–can use either Cephalosporins or Zosyn (piperacillin-tazobactam)

29
Q

How should you treat septic arthritis if the gram stain is negative?

A

–Vanc plus Cephalosporin

30
Q

How long is therapy required in septic arthritis?

A

2-4 weeks of IV antibiotics typically prescribed

If the organism is S. aureus, generally 4 weeks of IV antibiotic is required

Some will give 2 weeks of IV antibiotics followed by PO antibiotics for another 2 weeks

31
Q

What is Gonococcal arthritis?

A

•1 of 2 clinical manifestations of DGI (disseminated gonococcal infection), other being syndrome including tenosynovitis, dermatitis, and polyarthralgia/polyarthritis.

occurs in about 50% of DGI

32
Q

What patients typically get Gonococcal arthritis?

A

•4x more common in women; less than 40 years old, lower SE status, nonwhite ethnicity, MSM, multiple sex partners, illicit drug use

33
Q

Risk factors of Gonococcal arthritis?

A

•women during menstruation, pregnancy, or postpartum; complement deficiencies (particularly terminal components C5 to C8), and SLE

34
Q

Note on the pathogenesis of Gonococcal arthritis

A

Immune mechanisms (such as immune complexes) likely are involved and may account for low yield of cultures for N. gonorrheae in synovial fluid

35
Q

How does gonococcal arthritis present?

A

•Patients typically present with triad of dermatitis, tenosynovitis, and migratory polyarthralgia or polyarthritis.

Joint symptoms often severe and asymmetrical.

Fever, chills, generalized malaise present.

36
Q

What is this?

A

DGI

–Lesions of dermatitis seen in 2/3 of DGI patients; painless/nonpruritic, few in number. Macules, papules, pustules seen.

37
Q

Diagnosis of DGI?

A

Want to see the clinical triad and:

synovial fluid frequently with 50,000-100,000 cells, but not always. Aspirates from patients with DGI without frank suppurative arthritis will have lower cell counts.

–Cultures not commonly positive

38
Q

What are the risk factors for mycobacterial arthritis?

A

females over 65 of lower SE status

  • alcohol abuse, IVDU
  • HIV, immunosuppression
  • pre-exisitng joint disease
39
Q

How does MTb arthritis present?

A

MTB causes chronic granulomatous monoarthritis, usually the result of hematogenous dissemination associated with primary pulmonary TB

40
Q

Features of MTb arthritis?

A

In these cases fever and constitutional symptoms are ABSENT, there may not be signs of Tb infection anywhere else and the disease may lay latent for a long time before presentation

41
Q

How is MTb diagnosed?

A

A PPD will be positive in over 90% of cases and an AFB will be positive 80% of the time (acid-fast stain not as commonly positive)

  • if required, a synovial biopsy will show GRANULOMAS
  • PCR on synovial fluid
42
Q

How is MTb arthritis treated?

A

RIPE x8 weeks followed by INH adn RIF to complete 6 months

43
Q

What is this?

A

61 yo with pain in the R foot for 5 months, initial X-ray and CT negative. However repeat x-rays showed

possible septic arthritis in the R tarsometatarsal joint, aspiration of which showed no growth.

Biopsy done – showed minute fragments of viable bone, no inflammation. AFB stain/culture, fungal cultures, routine cultures done. 2 weeks later lab called saying AFB were growing in broth, later identified as MTB

44
Q

What are the stages of lyme disease infection?

A

Early infection stage I: erythema migrans (EM)

Early infection stage II: disseminated infection within several days-weeks of onset of EM

Late infection: stage III (persistent infection)

45
Q

How does early infection stage I of Lyme disease present?

A
  • erythema migrans (shown below)
  • malaise, fatigue,
  • HA, fever/chills, LAD regionally
46
Q

How does early stage II infection of Lyme disease present?

A

After several weeks to months, 15% of untreated patients develop frank neuro abnormalities (meningitis, encephalitis, etc.)

5% of untreated develop cardiac involvement (most commonly AV block)

  • you see secondary skin lesions that are smaller
  • malar rash
  • conjunctivitis
47
Q

How does late infection of Lyme disease present?

A

–60% of untreated experience intermittent attacks of joint swelling and pain, mostly in large joints, especially the knee; usually 1 or 2 joints at a time (lasting few weeks to months)

–Even in untreated patients, intermittent or persistent arthritis usually resolves completely within several years.

•Most respond to antibiotic treatment, but a small percentage experience antibiotic-refractory Lyme arthritis: persistent joint inflammation for months or even years after adequate antibiotic course.

48
Q

How is Lyme disease diagnosed?

A
  • Western blot
  • joint fluid draw: WBCs range from 500-110000/mm3 and msotly PMNs
49
Q

Why are prostethic joints so susceptible to infection?

A

After implantation, hardware is covered by host proteins favoring bacterial adherence (eg. fibronectin). Implants also compromise granulocyte function.

Implant-associated organisms growing as biofilm are protected from phagocytosis and many times from the action of antibiotics.

50
Q

Most common bugs for PJI (prosthetic joint infections)?

A

-S. aureus and Coag neg staph

Streptococci, GMB, Enterococci

51
Q

How is PJI diagnosed?

A

•threshold of leukocyte counts in synovial fluid much lower than for native septic joint (around 2,000-5000). Negative culture does not exclude diagnosis of PJI

52
Q

What occurs with viral arthritis?

A

•Often called immune complex arthritis: virus forms immune complexes with antibody that are deposited in joints and cause inflammation.

Small joints of hands most commonly affected; large joints can also be involved.

53
Q

Progression of viral arthrites?

A

Most cases of short duration and resolve spontaneously.

54
Q

Common causes of viral arthritis?

A
  • Rubella
  • Parvo B19
  • HCV, HBV
55
Q
A

Rheum/Musculoskeletal/Derm Week 2 (12 decks)

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