SM_242a: Bone and Joint Infections Flashcards Preview

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Flashcards in SM_242a: Bone and Joint Infections Deck (39)
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1

Describe the pathogenesis of septic arthritis

Septic arthritis

  • Hematogenous: vascular synovial membrane lacks a limiting basement membrane -> susceptible to deposition of bacteria during bacteremia
  • Direct innoculation: surgery, trauma, or contiguous spread from adjacent infected soft tissue or bone
  • Risk factors: abnormal joint, previous intraarticular steroid injection, immunosuppression, diabetes mellitus, malignancy, chronic renal failure, and IV drug abuse

2

Septic arthritis can occur via _____ or _____

Septic arthritis can occur via hematogenous spread or direct inoculation

3

Septic arthritis can spread ______ because the vascular synovial membrane lacks a limiting basement membrane, making it susceptible to deposition of bacteria during bacteremia

Septic arthritis can spread hematogenously because the vascular synovial membrane lacks a limiting basement membrane, making it susceptible to deposition of bacteria during bacteremia

4

Pathogenesis of septic arthritis depends on _____ and _____ factors

Pathogenesis of septic arthritis depends on bacterial factors and host inflammatory factor

5

Describe the role of bacterial factors in septic arthritis pathogenesis

Bacterial factors in septic arthritis pathogenesis

  • Joint disease or injury facilitates bacterial adherence
  • Staph aureus adhesins permit adherence to cartilage (MSCRAMMs)
  • Endotoxins promote cartilage breakdown

6

Describe the role of host inflammatory response in septic arthritis pathogenesis

Host inflammatory response in septic arthritis pathogenesis

  • Host-derived extracellular proteins promote bacterial attachment
  • Leukocyte-derived proteases and inflammatory cytokines cause cartilage and subchondral bone destruction
  • Joint inflammation increases intra-articular pressure, reducing capillary blood flow resulting in cartilage and synovial ischemia and necrosis

7

Most common etiology of septic arthritis is _____

Most common etiology of septic arthritis is Staphylococcus aureus

 

(Pseudomonas aeruginosa common in IV drug users and has predilection to involve fibrocartilaginous joints such as public symphysis and sternoclavicular and sacroiliac joints)

8

Describe clinical manifestations of septic arthritis

Clinical manifestations of septic arthritis

  • Pain and loss of function
  • Swelling, redness, and increased warmth
  • Fever and malaise
  • Single joint (monoarticular) in 80% of cases: knee most common in adults, hip infections in kids
  • Physical exam findings: infected peripheral joints (focal joint tenderness, inflammation, effusion, limited ROM), infected axial joints (focal tenderness over affected area, distant source of infection in half of patients

9

Arthrocentesis of septic arthritis reveals ______ WBCs with ______ neutrophils

Arthrocentesis of septic arthritis reveals > 50,000 WBCs with >90% neutrophils

10

Describe the differential diagnosis of fever and polyarthritis

Fever and polyarthritis differential diagnosis

  • Infectious arthritis
  • Crystal-induced arthritis: gout, pseudogout
  • Post-infectious/reactive arthritis: enteric/urogenital infection (Reiter's syndrome), rheumatic fever, inflammatory bowel disease
  • Rheumatoid arthritis and Still's disease
  • Systemic rheumatic illness: systemic lupus erythematosus, vasculitis

11

Empiric antibiotic therapy in septic arthritis is directed against ____ and ____

Empiric antibiotic therapy in septic arthritis is directed against Staphylococcus aureus and Neisseria gonorrhoeae

12

Describe gonococcal arthritis

Gonococcal arthritis (disseminated gonococcal infection)

  • Presentation: tenosynovitis, dermatitis, and polyarthralgia OR purulent monoarticular arthritis
  • Epigemiology: more common in women
  • Pathogenesis: occult bacteremia secondary to mucosal infection of the urethra, cervix, rectum, or oropharynx, asymptomatical mucosal infection more likely to result in disseminated gonococcal infection than symptomatic infection
  • Neisseriae gonorrhoeae

13

Describe Lyme Borreliosis

Lyme Borreliosis

  • Caused by Borrelia burgdorferi
  • Transmitted by Ixodes tick
  • Early infection: erythema migrans (expanding annular erythematous skin lesion), disseminated infection (fever, chills, secondary annular skin lesions, meningitis, cranial neuritis, carditis, and migratory arthritis)
  • Late infection: arthritis, chronic encephalopath
  • 7th nerve palsy

14

Describe viral arthritis caused by Parvovirus B19

Viral arthritis caused by Parvovirus B19

  • More common in women
  • Acute symmetrical polyarthritis of PIP and MCP joints with morning stiffness
  • Usually results in 2 weeks (although persistent polyarticular arthritis lasting several months occurs in some female patients)

15

Prosthetic joint infection is complicated by formation of _____ on the surface of prosthetic material, which _____ and _____

Prosthetic joint infection is complicated by formation of biofilms on the surface of prosthetic material, which slows immune response and limits antibiotic penetration

 

(likely Staphylococcus epidermidis)

16

_____ is pathognomonic for infection

Sinus tract is pathognomonic for infection

17

Describe treatment of prosthetic joint infection

Treatment of prosthetic joint infection

  • Debridement with retention of prosthesis and antibiotic therapy
  • One or two stage exchange and antibiotic therapy
  • Long-term antibiotic therapy suppression (paliative approach)
  • Implant removal without replacement and antibiotic therapy
  • Amputation needed in some cases of uncontrolled infection

18

_____ may be required if a prosthetic joint infection is uncontrolled

Amputation may be required if a prosthetic joint infection is uncontrolled

19

Describe antibiotic therapy for prosthetic joint infection

Antibiotic therapy for prosthetic joint infection: Staphylococcal

  1. Pathogen-specific IV antibiotic therapy + rifampin x2-6 weeks
  2. PO rifampin + companion oral drug (ciprofloxacin or levofloxacin) x3 months (THA infection) or x6 months (TKA infection)
  3. Consider indefinite chronic oral antimicrobial suppression with prosthesis debridement and retention

20

Describe pathogenesis of osteomyelitis

Pathogenesis of osteomyelitis

  • Hematogenous osteomyelitis: long bones/vertebrae/sternoclavicular joint, usually monobacterial
  • Contiguous infection: sacrum/pelvis/foot adjacent to neuropathic ulcers, usually polymicrobial
  • Escape host defeneses: adherence to damaged bone, persistence within osteoblasts, microorganisms coat themselves and underlying bone surfaces with biofilm

21

Osteomyelitis pathogenesis is either ____ or ____

 Osteomyelitis pathogenesis is either hematogenous or contiguous

22

Hematogenous osteomyelitis is usually ____ and occurs in ____, ____, and ____

Hematogenous osteomyelitis is usually monobacterial and occurs in long bones, vertebrae, and sternoclavicular joint

23

Contiguous osteomyelitis is usually ____ and occurs in the ____, ____, and ____ adjacent to ____

Contiguous osteomyelitis is usually polymicrobial and occurs in the sacrum, pelvis, and foot adjacent to neuropathic ulcers

24

Osteomyelitis escapes host defenses via _____, _____, and _____

Osteomyelitis escapes host defenses via adherence to damaged bone, persistence within osteoblasts, and microorganisms coating themselves and underlying bone surfaces with biofilm

25

Pathogenesis of osteomyelitis caused by Staphylococcus aureus involves _____ and _____

Pathogenesis of osteomyelitis caused by Staphylococcus aureus involves binding to fibronectin/collagen/sialylglycoprotein on bone surface and surviving in a dormant and phenotypically altered state within osteoblasts

 

(binding via MSCRAMMs, dormant state explains long incubation period and high relapse rate of Staph aureus osteomyelitis treated with a short course of antibiotics)

 

26

Biofilms ____, ____, and ____

Biofilms facilitate gene transfer of virulence factors and antibiotic resistance, evade host immune response via rapid changes in antigen expression, and antibiotic resistance by slowing diffusion and causing antibiotic malfunction

 

(biofilm: organized group of microorganisms in extracellular polymeric matrix)

27

Most common microorganism cause of osteomyelitis is _____

Most common microorganism cause of osteomyelitis is Staphylococcus aureus

28

Describe clinical manifestations of osteomyelitis

Clinical manifestations of osteomyelitis

  • Subacute-to-chronic presentation
  • Nonspecific pain around the involved site
  • Fever, chills, and local swelling and erythema in the proximity of the involved bone infrequently
  • Draining sinus tract over the involved bone occassionally 

29

Absent sepsis, in osteomyelitis ____ antibiotic therapy until adequate specimens are sent for culture

Absent sepsis, in osteomyelitis delay antibiotic therapy until adequate specimens are sent for culture

30

Vertebral ostoemyelitis involves _____ spread

Vertebral ostoemyelitis involves hematogenous spread

 

(organisms reach the well-perfused vertebral body via spinal arteries and spread from the end plate into the disk space and then to the adjacent vertebral body)

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