Bone Infections PDF

Bone Infections Chaya Prasad, MD, MBA  Osteomyelitis Complication of systemic infection OR primary solitary focus of disease Organisms include viruses, parasites, fungi, and bacteria Pyogenic bacteria and mycobacteria are the most common.  Rou...

Bone Infections Chaya Prasad, MD, MBA  Osteomyelitis Complication of systemic infection OR primary solitary focus of disease Organisms include viruses, parasites, fungi, and bacteria Pyogenic bacteria and mycobacteria are the most common.  Routes of Pyogenic Infections - hematogenous spread (common in healthy children) - extension from a contiguous site - direct implantation (after compound fractures or orthopedic procedures) - infections of the feet in diabetics. - Long bones commonly involved  Causative Organisms 80-90 % of culture positive cases - Staphylococcus aureus UTI/IV drug abusers - Escherichia coli, Pseudomonas, Klebsiella Direct spread - Mixed bacterial infections Neonatal period, - Haemophilus influenzae and group B streptococci Sickle cell disease - Salmonella infection  Changes of Acute Osteomyelitis Neutrophilic inflammatory reaction Necrosis of bone cells and marrow ensues within the first 48 hours. Periosteal inflammation and sizable subperiosteal abscess (especially in children) Contributes to the ongoing necrosis Dead bone is known as a sequestrum. Can create a draining sinus Infants epiphyseal infection may produce septic arthritis and permanent disability.  Changes of Chronic Osteomyelitis Chronic inflammatory cells Release cytokines, osteoclastic bone resorption, ingrowth of fibrous tissue, and the deposition of reactive bone at the periphery Newly deposited bone – involucrum, surrounds dead bone he histologic findings of chronic osteomyelitis include marrow fibrosis, sequestrum, and an inflammatory infiltrate of lymphocytes and plasma cells  Lab Tests of Acute Osteomyelitis CBC with differential - Leukocytosis Elevated inflammatory markers: ESR, CRP Cultures – ID and c/s Bone aspirate cultures Bone biopsy (rare)  Acute Osteomyelitis Bone destruction Live osteocyte with nucleus Inflammation Dead osteocyte Inflammation 8 Dead Bone Gram Stain Organisms PMN Chronic Osteomyelitis 11 Draining Osteomyelitis Sequestrum Involucrum  Lab Tests Bone biopsy – H&E Microbiological cultures Special studies if cultures negative  Chronic Osteomyelitis Mononuclear inflammatory cells Dead osteocytes  Mycobacterial Osteomyelitis Developing countries and now in the developed world 1% to 3% of individuals with pulmonary/extrapulmonary TB Indolent but may present with localized pain, low-grade fevers, chills, and weight loss Solitary infection vs disseminated in immunocompromised Histologic - caseous necrosis, granulomas Tuberculous spondylitis (Pott disease) - destructive infection of vertebrae. Tuberculous Vertebral Osteomyelitis  Lab tests Smears Special stains Cultures Molecular tests Biopsy - rare Tuberculous Osteomyelitis Giant cells Necrosis Bone Acid Fast Stain  Septic Arthritis Infection via hematogenous, direct inoculation, or from contiguous spread Infectious arthritis serious - rapid, permanent joint destruction. H. influenza arthritis - in children younger than 2 years of age S. aureus - in older children and adults Gonococcus - late adolescence and young adulthood Salmonella - sickle cell disease Joint aspiration - diagnostic  Lab tests CBC with differential Inflammatory markers Blood cultures Synovial fluid aspiration – smears, special stains, cultures (ID and c/s) Septic Arthritis Organisms 22  Lyme Arthritis Lyme disease - infection by Borrelia burgdorferi, transmitted by deer ticks of the Ixodes ricinus complex New England and mid-Atlantic states Migratory arthritis in chronic stage of disease Lab diagnosis - serologic testing for anti-Borrelia antibodies Cellular (especially TH1) and humoral responses to Borrelia outer surface protein A (late autoimmune arthritis) Histopathology - chronic synovitis marked by synovial hyperplasia, fibrin deposition, mononuclear cell infiltrates and onionskin thickening of arterial walls (resembles RA)  Lab Tests for Lyme Disease EIA or ELISA for total Lyme titer or IgG and IgM titers If EIA / ELISA test results come back positive or equivocal, Western blot IgG and IgM titers are performed Lyme titers should be done if the above tests are positive PCR in synovial fluid (for spirochetes) EIA – enzyme immunoassay ELIZA - enzyme-linked immunosorbent assay Long corkscrew shaped organism  The End Thank you Optional Content – Board Style Questions  Question 1 A 52-year-old male presents to the emergency department with acute onset of right knee pain, swelling, and fever for the past two days. He reports difficulty bearing weight on the affected leg and denies any recent trauma. His medical history is significant for type 2 diabetes mellitus. On examination, his right knee is warm, erythematous, swollen, and extremely tender to palpation, with decreased range of motion. Laboratory studies reveal a white blood cell count of 16,000 cells/mm³ and an elevated C-reactive protein level. Arthrocentesis yields purulent synovial fluid with a white blood cell count of 90,000 cells/mm³, predominantly neutrophils. Gram stain of the fluid shows gram-positive cocci. Histopathological examination of the synovium reveals an acute inflammatory infiltrate with numerous neutrophils and signs of synovial tissue destruction. What is the most likely diagnosis? A. Gouty arthritis B. Reactive arthritis C. Septic arthritis D. Rheumatoid arthritis E. Pseudogout  Answer and rationale A. Gouty arthritis - Incorrect. In this case, there is evidence of infection with gram-positive cocci, which is not consistent with gout. B. Reactive arthritis - Incorrect. The presence of gram-positive cocci in the synovial fluid rules out reactive arthritis. C. Septic arthritis - Correct. Septic arthritis is characterized by the rapid onset of monoarticular joint pain, swelling, and fever. Synovial fluid analysis typically shows a very high white blood cell count (often >50,000 cells/mm³) with neutrophilic predominance. The presence of gram-positive cocci on Gram stain and histopathological findings of acute inflammation and synovial destruction confirm the diagnosis. D. Rheumatoid arthritis - Incorrect. Rheumatoid arthritis is a chronic autoimmune disease that generally presents with symmetrical joint involvement and morning stiffness. History is not consistent with this diagnosis E. Pseudogout - Incorrect. Pseudogout does not cause purulent synovial fluid or involve gram-positive cocci, as seen in this case  Question 2 A 25-year-old sexually active man presents to the clinic with acute onset of right knee pain, swelling, and fever over the past two days. He denies any history of trauma. On physical examination, the right knee is swollen, erythematous, warm, and tender, with a significantly decreased range of motion. His temperature is 38.5°C (101.3°F). Laboratory results show a white blood cell count of 14,500/µL and an elevated C-reactive protein. Arthrocentesis of the right knee yields purulent synovial fluid with a leukocyte count of 80,000/µL, and Gram stain reveals intracellular gram-negative diplococci. A biopsy of the synovial membrane reveals acute inflammation with neutrophilic infiltration and fibrin deposition. Which of the following is the most likely causative organism? A) Staphylococcus aureus B) Streptococcus pneumoniae C) Neisseria gonorrhoeae D) Pseudomonas aeruginosa E) Borrelia burgdorferi  Answer and Rationale A) Staphylococcus aureus: Incorrect. In a sexually active young adult with gram- negative diplococci seen on Gram stain, Neisseria gonorrhoeae is the more likely culprit. B) Streptococcus pneumoniae: Incorrect. Streptococcus pneumoniae is not the most common pathogen in a young, sexually active individual. C) Neisseria gonorrhoeae: Correct. Neisseria gonorrhoeae is the most common cause of septic arthritis in young, sexually active individuals. The presence of intracellular gram-negative diplococci in the synovial fluid strongly supports this diagnosis. D) Pseudomonas aeruginosa: Incorrect. Pseudomonas aeruginosa is not commonly found in otherwise healthy, sexually active young adults. E) Borrelia burgdorferi: Incorrect. Borrelia burgdorferi causes Lyme disease does not present with acute purulent arthritis and would not be associated with the Gram stain findings described.