Microbiology of Osteomyelitis and Arthritis

Snapshot

A 26-year-old man presents to his primary care physician with pain in his knee, elbow, and wrist and reports subjective fever. He is sexually active with two partners and uses condoms inconsistently. On physical examination, there is tenderness of the tendon sheath upon palpation and a warm mildly swollen joint with asymmetric involvement of the knee, wrist, and elbow. (Gonococcal arthritis)

Introduction

Clinical definition
- osteomyelitis
  - infection of the bone and marrow
- septic arthritis
  - infection of the joint
Pathophysiology
- pathoanatomy
  - osteomyelitis
    - hematogenous spread
      - more common in children
      - usually monomicrobial
    - contiguous spread from adjacent infection
      - can be polymicrobial and monomicrobial
    - direct micro-organism inoculation
      - e.g., surgery and trauma
  - septic arthritis
    - hematogenous spread
      - most common
    - direct micro-organism inoculation
      - e.g., trauma and iatrogenically (surgery and arthrocentesis)

Select Microbes Causing Osteomyelitis

Select Microbes Causing Osteomyelitis
Microbe	Comments
Staphylococcus aureus	Most common overallVertebral involvementIntravenous drug useAnother common cause includes coagulase-negative staphylococci
Salmonella enteridis	Sickle cell anemia can also be due to S. aureus
Pseudomonas aeruginosa	Trauma (e.g., puncture wound to foot), diabetics, and intravenous drug users
Neisseria gonorrhoeae	Sexually transmitted infections can lead to osteomyelitis, although septic arthritis is more common
Staphylococcus epidermidis	Prosthesis
Mycobacterium tuberculosis	Vertebral osteomyelitis (Pott’s disease, also known as Tuberculous spondylitis)
Pasteurella multocida	Animal bites/scratches
Group B Streptococcus	Infants younger than 3 months

elect Microbes Causing Infectious Arthritis

Select Microbes Causing Infectious Arthritis
Microbes	Comments
Staphylococcus aureus	Most commonarthritis can be mono- or poly-articularcan be accompanied with cellulitis, abscess, intravenous drug use, osteomyelitis, or endocarditis
Streptococci and other gram-positive organisms	Second most common cause
Pseudomonas aeruginosa	Can be seen in intravenous drug users
Neisseria gonorrhoeae	Seen in sexually active young adultspresents with polyarticular arthritisDisseminated gonococcal infection