Osteomyelitis (Bone infections)

Question 1

What are the categories of osteomyelitis?

Answer 1

• hematogenous (seeding of bone related to a previous bacteremia; abcess -> blood -> bone)
  
  • usually monomicrobial in kids
• direct implantation (from penetrating injury)
• contiguous (direct spread of bacteria from an overlying wound/diabetic or pressure ulcer)
  
  • usually polymicrobial in adults
• infection of prosthetic device

Question 2

What are the common pathogens of hematogenous osteomyelitis?

Answer 2

• Staph aureus (most common, 70-90% of cases in children)
• Strep
• Gram negatives
• Mycobacterium tuberculosis
• Salmonella (in sickle cell patients)

Question 3

What are the common pathogens of direct implantation osteomyelitis?

Answer 3

• Pseudomonas aeruginosa (common in nail injuries with sneakers; likes to live in water/sweaty shoes)
• Others possible

Question 4

What are the common pathogens of contiguous osteomyelitis?

Answer 4

• Staph aureus (most common)
• Gram negatives
• Strep
• Anaerobes
• Candida (fungal)

Question 5

What are the common pathogens of prosthetic joint osteomyelitis?

Answer 5

• Coagulase negative staphylococci
• staph aureus
• gram negatives
• strep
• propionibacterium acnes (name change to Cutibacterium… common in head and neck; shoulder replacement/craniotomies)

Question 6

What pathogens are more frequent in patients with UTIs or infections from IV drug use?

Answer 6

**Gram negatives;

• E coli
• Pseudomonas
• Klebsiella
• Enterobacter

Question 7

What causes bone infection in patients with TB?

Answer 7

1-3% of patients with TB will have bone infections, can be;

• through the bloodstream (disseminated disease)
• direct extension (from pulmonary focus to ribs or vertebral bodies)

Question 8

What STD can infect bone?

Answer 8

Syphilis (in chronic or congenital cases)

Question 9

What may occur due to damage to the periosteum?

Answer 9

• pieces of dead bone (sequestrum)
• new external bone formation (involucrum) around infected bone
• localized abscesses (Brodie’s abscesses) within bone

Question 10

What imaging/testing is required to diagnose osteomyelitis?

Answer 10

• X-rays may be negative early in infections (NOT very sensitive for osteomyelitis)
• More effective;
  
  • Bone/WBC scans
  • MRI
• Bacteria causing osteomyelitis can be obtained from bone biopsies or sometimes from blood cultures
  
  • Cultures of open ulcers= notoriously unreliable (bacteria in the bone underneath may be different)

Question 11

When is fever seen concurrently with osteomyelitis?

Answer 11

• fever is common in acute osteomyelitis
• RARE in chronic cases (can have quiescent infection for years)

Question 12

What is a biofilm?

Answer 12

• aggregations of microorganisms adherent to a surface, particularly a hard surface like bones/teeth/prosthetic material
• adherent microorganisms are frequently embedded in a matrix they produce (slime/extracellular polymeric substance/glycocalyx)
• more likely to be resistant to antibiotics than suspended planktonic organisms

Question 13

What is the common treatment for osteomyelitis?

Answer 13

• long courses of antibiotics (6 weeks IV, months oral)
  
  • Rifampin especially useful in treating biofilms and has markedly improved success in treating prosthetic joint infections
  • only useful if the bone is covered with tissue (otherwise new organisms can continuously invade)
• surgery may be needed to remove sequestra or prostheses

**broad spectrum; IV vancomycin + oral rifampin for 6 weeks followed by oral doxycycline and rifampin for 6 months