Bone, Joint, and Muscle Infection - Cross Flashcards
Septic arthritis definition?
Typically refers to bacterial infection in a joint.
Septic Arthritis main route of infection? Others?
Usually hematogenously acquired
Other routes: Direct inoculation of bacteria into joint through surgery, trauma; contiguous spread from adjacent infected soft tissue or bone
Most common bug in “Step on a Nail” septic arthritis
Pseudomonas Aeruginosa
Most common bug in “Bit by my dog/cat” septic arthritis
Pasteurella Multocida
Most common bug in sickle cell septic arthritis
Salmonella
Pseudomonas Aeruginosa seen in these patients with septic arthritis?
IVDU (IV Drug Use), iatrogenic septic joint post surgical procedure/injection
Most common bug causing septic arthritis?
Staph aureus
Most important risk factor in septic arthritis?
preexisting abnormal joint architecture (i.e. RA, osteoarthritis, gout)
Risk factors for septic arthritis?
Abnormal joint architecture (most important), RA, osteoarthritis, gout, advanced age, diabetes, IVDU, immunosuppression, endocarditis
2nd most frequent cause of septic arthritis?
Strep; GAS, GCS, GGS
Neonate has septic arthritis. What bug? This bug causes septic arthritis in what other patients?
Group B strep, also in diabetics, those with malignances
Sacroiliac joint arthritis. Bug? Source?
Brucella from unpasteurized milk. Super rare. Dr. Cross hasn’t seen it.
Sternoclavicular septic arthritis or clavicular osteomyelitis. Most likely in what patients?
IV drug users
RA patients most likely to get septic arthritis from what bug?
Staph aureus
Most common joint affected in septic arthritis?
The knee ( around 50%), mono-articular in 80-90% of cases
Most common joint affected in septic arthritis in children?
The hip
What bug causes gas gangrene?
Clostridium perfringens
Typical clinical presentation of a patient with septic arthritis
Intense pain and loss of function of that joint over 1-2 weeks; swelling, erythema, and increased joint warmth
What is characteristic of children with a septic hip?
they hold the hip in a flexed and externally rotated position, resist all ROM
Dx of septic arthritis requires what?
arthrocentesis of affected joint
Arthrocentesis facts
> how many cells usually required to make dx?
What type of cells are most abundant?
> how many cells pretty much is a dead giveaway for septic arthritis
Blood culture usually +?
> 50,000 usually septic
mostly neutrophils
> 100,000 = “you can pretty much bet this is a septic joint”
Blood cultures not often +
Most important thing to look for when aspirating a joint that is suspected to be septic?
The presence of crystals, if crystals are present then it’s gout, not septic arthritis
Nonspecific lab findings seen in septic arthritis
Leukocytosis, elevated ESR and/or CRP
Early X-ray findings in septic arthritis
periarticular soft tissue swelling, nml osseous structures
Late X-ray findings in septic arthritis
Joint space loss, bony erosion/destruction
Ultrasound of septic joint is useful for what?
assess for presence of effusion and to guide needle aspiration if needed
Who are you going to immediately call if pt has septic arthritis?
Future drew aka ortho to come for drainage +/- irrigation and debridement
What bug causes a migrating arthritis
Gonococcus
Presentation of gonococcal arthrits
Triad of dermatitis (this is key), tenosynovitis, and migratory polyarthralgia
Epidemiology of Gonococcal arthritis. List a few
4x more common in women; <40 years old, lower socioeconomic status, multiple sex partners, illicit drug use
Pathogenesis of Gonococcal arthritis
Results due to occult bacteremia; infection could have been contracted days to months prior to dissemination
Risk factors for gonococcal arthritis?
Women during menstruation, pregnancy, or postpartum; complement deficiencies (C5-C8)
General outcome of blood cultures
around 25% are positive; don’t be fooled by negative blood cultures
Joints that gonococcal arthritis normally affects
Knees, wrists, ankles
What is this? What disease is this associated with? Early or late in progression of disease?
Erythema migrans aka Bullseye rash = Early Infection Stage 1 Lyme disease
Common bug that causes lyme disease?
Borrelia burgdorferi
Lyme disease common where (geography)?
Common in northern states; NOT common in TN or Missouri.
- Hey lets go picket in front of the Infectious disease convention. Theyll start listening to us then.
Stages of Lyme disease?
Stage 1 (early infection): erythema migrans; classic “bullet” rash
Stage 2 (early infection): Secondary skin lesions similar to initial lesions, but smaller; malar rash and conjunctivitis
Stage 3 (Persistent infection): intermittent attacks of joint swelling, especially large joints like the knee; even in untreated patients persistent arthritis normally resolves completely over several years
Test used to diagnose Lyme disease
Lyme western blot test
Alpha toxin associated with what bug? Main effect?
clostridium perfringens, causes hemolysis leading to anemia
Gas gangrene in a patient causes what?
myonecrosis, necrotizing fasciitis
Leukocyte threshold for diagnosis of prosthetic joint infection
Threshold is much lower for leukocytosis in the synovial fluid when compared to a nml joint; prosthetic joints don’t have the amount of vascular access for inflammatory cells
Treatment for prosthetic joint infection
REMOVE THE PROSTHESIS; prolonged abx therapy
Conjunctivitis, palsies, and meningitis are associated with what disease?
Early Infection Stage II of Lyme Disease
Features: include secondary skin lesions similar to initial lesions, but smaller; malar rash and conjunctivitis
- heart and nervous system including palsies and meningitis
Pt has abscess on spine, whats your likely dx?
Pott’s disease (MTB osteomyelitis of spine)
Likely source and route leading to Pott’s Disease
TB of lung spread hematogenously to spine
What bug causes double zone of hemolysis on blood agar?
clostridium perfringens
Osteomyelitis due to candida infection seen in what patients? Other bugs common to this subset of patients?
IV drug users. Staph aureus, pseudomonas, candida, and serratia
Causes of viral arthritis?
Rubella, Parvo B19, HCV, HBV
Characteristic course of viral arthritis?
short duration, most resolve spontaneously; small joints of the hands most commonly affected
How is the inflammation caused in viral arthritis
Immune complex formation; deposition in the joints causes inflammation
Most common causes of osteomyelitis
Common (>50% of cases) = Staph aureus, coag - staph (S. epidermidis, etc)
Less common (>25% of cases) = streptococci, enterococci, gram - (pseudo in someone stepped on a nail), anaerobes, MTB
Pathogenesis of staph aureus causing osteomyelitis?
Expresses high affinity adhesions to components of bone matrix that express fibronectin, laminin, collagen, etc
- it was bolded in her notes.
Presentation of osteomyelitis
Nonspecific pain around the involved site with absence of systemic signs/symptoms
In osteomyelitis, what usually alerts you to the source?
Location, location, location
Osteomyelitis as a result of hematogenous seeding in adults is usually what type?
vertebral osteomyelitis
Hematogenous long bone osteomyelitis: mono or polymicrobial?
monobacterial
Contiguous infection osteomyelitis: mono or polymicrobial?
polymicrobial
Foot osteomyelitis in diabetics is usually due to what route of infection?
result of contiguous spread
Foot osteomyelitis after nail puncture usually due to what route of infection?
Result of direct inoculation
Long bones of the lower extremity are the most common location of infection in what subset of patients with osteomyelitis?
Acute hematogenous osteomyelitis in children, obviously a result of hematogenous seeding
Patient comes in with neck/back pain symptoms. What is an important question to ask?
Have you had recent injections in your back/neck. Rare but could be vertebral osteomyelitis due to iatrogenic cause (like injecting a long ass needle in someones neck)
Complement deficiency risk factor for what? What complements specifically?
gonococcal arthritis, C5-C8
