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OSTEOMYELITIS Micro Exam 6 (Pathogenesis Long bones in children…

- - - - Hematogenous & contiguous focus osteomyelitis
        
        Adhere to fibrinogen, fibrinonectin, laminin, collagen, bone, sialoglycoprotein
      - Virulence Factors
        
        1. Microbial Surface Components (MSCRAMMS)
        
        Clumping factor A = coagulase & binds platelets
        
        Fibronectin Binding Proteins (FnBPA & B)
        
        rapidly coats implanted foreign bodies in vivo
        
        may play role in binding to implants
        
        2. Virulence determinants of bacteria
        EX:
        
        Taken up by osteoblasts & develop resistance
        
        Assoc. w/ Chronic Osteomyelitis (high relapse rate when treated w/ short duration therapy)
        
        Protein A :link: Fc part of IgG
        &
        :forbidden:Opsinization by PMNs
        
        Secretes Superantigens
        
        Avoids cellular & humoral immune system
        
        Enterotoxins
        
        SEA
        
        SEB
        
        TSST-1
        
        3. Biofilm Formation
        
        Polysacc., protein, & extracellular DNA
        
        Coat organic & inorganic surfaces
        
        Create bacteria community
        
        Density & depth of biofilm protects from antimicrobials & antibodies
      - :pill: Treatment:
        
        MSSA: Nafcillin, Oxacillin, Fefazolin
        
        MRSA: Vancomycin, Clindamycin
    - - Staph Epidermis
      - Staph saprophyticus
  - - - Pediatric ostoarticular infections, bacteremia, endocarditis
        
        Colonized posterior pharynx of young children
        
        Transmitted child to child (close contact)
        
        Daycare
      - ID:
        
        Improved culture methods
        
        Nucleic Acid Amplification techniques
        
        Grows SLOW in high density microbiota background
      - Virulence Factors
        
        RTX Toxin :star:potent
        
        Pore-forming cytotoxin
        
        Type IV Pili = Adhesin
        
        Twitching motility
        
        Adhere substrate > contract via polymerization/depolarization
        
        Same pilus = DNA transfer
      - S&S:
        
        Subtle
        
        Normal levels of acute phase reactants
        
        HIGH INDEX OF SUSPICION required
      - :pill: Treatment:
        
        B-lactams Penicillin or Cefazolin for Chronic Osteomyelitis
        
        Typically respond well to antibiotics, except in cases of endocarditis
- - - - NECROSIS
        
        Sequestrum
        
        Separated pieces of dead bone
        
        Hallmark of Chronic Osteomyelitis
        
        Involucrum
        
        New bone formation in area of periosteal damage
    - - Slow
        
        Vetebral osteomyelitis
      - Fast
        
        Prosthetic devices
        
        Compound fractures
  - - - Associated with SEPTIC ARTHRITIS
        
        Infection from metaphysis spreads
        
        Breaks through cortex w/capsular reflection of joint
        
        Secondary infection
        
        Joints: long bone metaphysis w/in joint capsule reflections (knee, hip, shoulder)
        
        Infants:
        
        long bones --> quickly becomes septic arthritis
    - - Early Empiric Antibiotic for AO depends on prevalence of CA-MRSA
        Switch to ORAL meds with clinical improvement and decrease CRP
  - - - Associated with Deep/Extensive ULCERS (pedal)
        
        fail to heal after several weeks of care
        
        Esp. if ulcer is over bony prominence
        
        DM Patients
        
        Probe bone
        
        Probing bone sufficient for diagnosis
      - Associated with Poor Management
        
        6 wks post-orthopedic repair & oral antibiotics
        
        No debridement surgery of malleolar fracture
        
        S. aureus infection