MSK Infectious Diseases Flashcards
What is osteomyelitis?
Infection of the bone.
What is the most common pathogen in osteomyelitis infections?
Staph Aureus.
Approximately how many cases of osteomyelitis occur per year?
Estimated 50,000 cases annually.
What increases the risk of osteomyelitis?
Increases with age:
*PVD
*T2DM
*procedures.
Who is most affected by pediatric osteomyelitis?
Males, with S. Aureus being the most common pathogen and hematogenous spread being the most common route.
What other pathogens can cause osteomyelitis in other populations?
Sickle cell patients m/c salmonella; Neonates m/s Group B strep.
What are the most common locations of occurrence of osteomyelitis?
Vertebral (most common site in adults), long bones in adults with internal fixation devices, joint infections (ankle/elbow), sternal, and foot (diabetes, arterial insufficiency, neuropathy, and s/p foot surgery).
What are the risk factors of osteomyelitis?
Bacteremia or endocarditis, orthopedic hardware, chronic poorly healing wounds, diabetes mellitus, IV drug use, PVD, trauma/open fractures, and neuropathy.
How will patients typically present with osteomyelitis?
Acute: may have fever/chills, erythema, swelling, warmth. Chronic: same as acute with fewer constitutional symptoms.
What lab tests will be ordered for osteomyelitis and what will the results be?
VERY elevated CRP, elevated ESR, elevated WBC (>70% will be polymorphonuclear neutrophils), and blood culture.
What is the gold standard for diagnosing osteomyelitis?
Bone biopsy.
What diagnostic test has the highest combined sensitivity and specificity for osteomyelitis?
MRI, helps determine extent of soft tissue involvement.
What is the typical treatment and management of osteomyelitis?
Prescription of antibiotics (empirically Vancomycin or third/fourth generation cephalosporin), surgical irrigation and debridement. May need antibiotic-impregnated cement beads for local delivery in severe cases.
In what other ways should osteomyelitis patients be managed?
Control T2DM, smoking cessation, address malnutrition, and exercise for angiogenesis.
What is septic arthritis?
Joint inflammation secondary to infectious cause.
Is septic arthritis most commonly in children or adults?
Children, incidence peaks between ages 2-3, males > females.
What joint is most commonly affected by septic arthritis?
Knee.
What joints are more likely to be affected in IV drug users?
Sternoclavicular and sacroiliac joints.
What is the most common pathogen that causes septic arthritis?
Staph Aureus.
Is septic arthritis typically due to hematogenous or contiguous spread?
Hematogenous.
What are the predisposing conditions for septic arthritis?
RA, OA, crystal arthropathies, previous joint damage, and IV drug use.
What symptoms will a patient with septic arthritis present with?
Fever, joint pain (especially with movement), swelling, pediatric patients will avoid use of joint, and limp (LE).
What tests will be ordered in patients suspected to have septic arthritis?
WBC (>10,000/mcL in 50% of patients), synovial fluid culture (positive in 70-90% of patients), gram stain (positive in 75% of cases), and imaging (not specific but may demonstrate joint fluid, soft tissue).
How is septic arthritis treated?
After obtaining culture, empiric antibiotic (vancomycin or 3rd or 4th gen cephalosporin), then narrow down once results have been received. Encourage active motion exercise; early detection improves prognosis.
What is periprosthetic joint infection (PJI)?
Small amounts of microbes get into a joint and create a biofilm which can create significant infections.
What is the incidence of PJI after a THA or TKA?
Approximately 2%, risk highest in early post-operative period, but extends through the lifetime of the prosthetic.
What are the top two reasons for failure of TKA?
PJI and polyethylene wear.
What is the most common pathogenic cause of skin and soft tissue infections?
S. Aureus.
What is the most common pathogenic cause of lower respiratory tract infections?
Streptococcus pneumoniae.
What are the most common pathogenic causes of UTI?
Escherichia coli, Enterobacterales spp, including Klebsiella.
What are the most common pathogenic causes of gastrointestinal infections?
Bacteroides, Salmonella, and Streptococcus gallolyticus.
What is the most common pathogen obtained from recent dental procedures?
Viridans streptococci.
What is the most common pathogen that causes infection to intravascular devices?
S. epidermidis.
Why can a patient not have a corticosteroid injection within 3 months of surgery?
Infection risk.
What are the potentially modifiable presurgical risk factors for periprosthetic joint infection?
Anemia, injection drug use, malnutrition, obesity, receipt of intraarticular injection in prior 3 months, and tobacco use.
What type of bacteria most commonly causes periprosthetic joint infection?
Aerobic gram positive: Coagulase-negative staphylococcus species, S. Aureus.
What symptoms will the patient present with in the case of PJI?
Hx joint replacement, progressive joint pain, swelling, erythema, warmth, may have drainage, fever not common.
What diagnostics will be used in PJI?
CBC (high percentage of neutrophils), blood cultures, synovial fluid (>1500 leukocytes/mL, PMNs >65%, CRP >6.0 mg/L, pos leukocyte esterase, pos Alpha-defensin), and X-ray (may show evidence of loosening of hardware).
