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Infectious Diseases > Bone And Joint Infections > Flashcards

Bone And Joint Infections Flashcards

1
Q

What are the causes of the rise in bone and joint infections?

A 
Aging populations
Epidemics of obesity/diabetes
Invasive medical/surgical procedures
High speed motor vehicle accidents
Physical and aggressive sports
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2
Q

What is the most common cause of bone and joint infections?

A

Staphylococcus aureus

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3
Q

What is osteomyelitis?

A

Inflammation of the marrow bone
Loosely used to refer to infection in any part of the bone
Involves periosteum, cortical bone, medullary cavity

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4
Q

What is the epidemiology of osteomyelitis?

A

Most often in preschool children (refuse to stand on one leg)
Twice more likely to occur in males than females
Occur with foot puncture at a much higher in diabetics

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5
Q

What are the routes of entry of osteomyelitis?

A

Contiguous- spread from nearby soft tissue infection
Direct implantation- trauma/surgery
Hematogenous route via nutrient arteries

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6
Q

What are the causes of osteomyelitis in infants less than 1 year?

A

Staphylococcus aureus
Streptococcus agalactiae (group B strep)
E.Coli (inhalation during child birth)

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7
Q

What are the causes of osteomyelitis in children?

A

Staphylococcus aureus
Streptococcus pyogenes (Group A)
Haemophilus influenzae

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8
Q

What are the causes of osteomyelitis in adults?

A

Staphylococcus aureus
Staphylococcus epidermis
Mycobacterium tuberculosis
Gram negative rods

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9
Q

What are the causes of osteomyelitis in IV drug user?

A

Pseudomonas aeruginosa
Staphylococcus aureus
Mostly affect cervical vertebra compare to lumbar vertebra in other cases

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10
Q

What is the pathogenesis of osteomyelitis?

A

Microbes seed bones
Infection occurred if microbe adhere to bone or implant
Adherence depends one bone fibrinogen, laminin, collagen and bacterial adhesins
Bacteria produce a glycocalyx biofilm after adherence
Biofilms prevent bacterial killing by host and antibiotics
PMN release reactive oxygen intermediates, toxins and enzymes that damage bones

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11
Q

What are the types of osteomyelitis?

A

Acute- develops over days to weeks
Chronic- over weeks, months and may persist for years
Hematogenous-primarily in children and elderly
Contiguous- from a nearby infection, trauma, surgery

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12
Q

What are the characteristics of acute osteomyelitis?

A

Bugs
PMNs
Congested and thrombosed blood vessels
Less than 6 weeks

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13
Q

What are the characteristics of chronic osteomyelitis?

A

Presence of necrotic bone and mostly mononuclear cells
Few organisms to be seen on staining
Granulation/fibrosis replaces bone resorbed by osteoclasts

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14
Q

What are the characteristics of osteomyelitis in children?

A

Usually hematogenous and involves a single bone
Usually involves long bone
Bugs enter via enter artery to metaphyseal capillary loops
Sharp turns at distal metaphysis slows blood flow
Abrupt onset, fever, soft tissue swelling
If only osteomyelitis no pain on active or passive motion of the joints

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15
Q

What are the characteristics of osteomyelitis in neonates and infants?

A

Thin cortical bone composed primarily of woven bone

Stimulation of periosteum leads to new bone growth (involucrum)

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16
Q

What are the characteristics of hematogenous osteomyelitis in adults?

A

Rarely involves long bone due to changes in vascular anatomy
More common in persons older than 45 years
Source isn’t always evident
Most common in vertebrae
Involvement of adjacent vertebral bodies and intervening disc rules out metastatic bone lesion
Lack of valve provides a route for the spread of infection

17
Q

What are the characteristics of vertebral osteomyelitis?

A

Usually in elderly
Low grade fever and progressive worsening of back pain
Usually unrelieved by analgesics

18
Q

Wha are the characteristics of osteomyelitis after bone fractures?

A

Close fracture- one bug
Open fracture- often polymicrobial
As patient begins to bear weight pain reappears

19
Q

What are the characteristics of diabetic foot osteomyelitis?

A

Poor vascularity and neuropathy
Starts with an ulcer (lower extremities)
No pain.inflammation due to vascularization
Fever in usually absent

20
Q

How to diagnose osteomyelitis ?

A

In Children-avoid biopsy may damage the growth plate, rely on blood cultures and empiric therapy
In adults- blood culture is the gold standard, deep tissue sample is preferred
Elevated ESR and CRP levels are non specific
ESR peaks in 3-5 days, declines 1-2 week after therapy
CRP peaks in 2 days declines in day 6th after therapy

21
Q

What is the therapy for osteomyelitis ?

A

Adequate tissue sample for culture
Specific antimicrobial regimen (4-6 weeks)
Empiric therapy is usually started in children
In diabetics- amputation or debridement may be required

22
Q

What is septic arthritis?

A

Arthritis that results from infection of one or more joints by a microorganism usually bacterial
Most commonly caused by S.aureus and Neisseria gonorrhea
Acute- involves a single joint and destructive to articular cartilages
examine inflamed joints promptly for infectious arthritis

23
Q

What is the epidemiology of septic arthritis?

A

More common in children than adults
High incidence in age group younger than 15 and older than 55
In infants- usually involves hip
In children- most commonly affects knee
IV drugs users- sternoclavicular and sacroiliac joints

24
Q

What are the routes of bacterial entry?

A 
Hematogenous route
Dissemination from osteomyelitis
From adjacent soft tissue infection
Diagnostic/therapeutic measures
Penetrating injuries
25
Q

What are the etiologies for septic arthritis?

A

Neonate- S. Agalactiae, S. Aureus. GNR
<2- S. Aureus, Kingella kingae, H.influenzae
>2- S. Aureus, S.pyogenes
Sexually active young adults-N.gonorrhoea, S. Aureus
Elderly adults- S.aureus, Streptococcus, GNR
early infection (prosthesis)- S. Epidermis, S.aureus
Late infection (prosthesis)-GPC, anaerobes

26
Q

What are the 2 types of septic arthritis ?

A

Non- gonococcal

Gonococcal

27
Q

What are the characteristics of non gonococcal septic arthritis?

A

Mostly in the very young, very old and in IV drug users
Mortality rate is high with S. Aureus septic arthritis
Moderate to severe pain around joint
Swollen joint
Can impaired growth in children and lead to limb discrepancy
May result in AVN of the femoral head
Sepsis in elderly and I/C patients

28
Q

What are the characteristics of Gonococcal septic arthritis ?

A

Gonorrhea is more common in men but gonococcal infection mostly occurs in female
Alkaline vaginal pH makes organisms more resistant to host
Manifest with classic triad: dermatitis,tenosynovitis,and migratory polyarthritis
Dermatitis on trunk and exterior surface of distal extremities
Blood culture almost always negative

29
Q

What are the characteristics of Lyme arthritis?

A

Due to untreated infection by B. Bugdorferi
Symptoms wax and wane over months without treatment
Commonly in the knees but can occur in other large joints
Can persist even with correct treatment: antibiotic refractory lyme arthritis

30
Q

What are the characteristics of Syphilitic arthritis?

A

Osteochondritis of long bones in early congenital syphilis
Late congenital syphilis between 8-15 year olds chronic painless synovitis with effusion in knee and elbow
Tertiary syphilis may be due to sensory loss

31
Q

What are the characteristics of fungal arthritis?

A

Unusual caused by invasive fungi

Mostly monoarticular in large, weight bearing joints (knee)

32
Q

What are the fungi that cause arthritis?

A 
Blastomyces dermatitis
Candida albicans
Coccidioides immitis
Histoplasma capsulatum
Sporothrix schenckii (gardeners)
33
Q

What are the characteristics of viral arthritis?

A

Occurs in younger patients
Usually during viral prodrome
Polyarthritis and usually symmetrical in small joints (wrists)
Self limited

34
Q

What are the etiologies of viral arthritis?

A 
Hepatitis A
Hepatitis B
Hepatitis C
Parvovirus B19
Rubella virus
HIV
35
Q

What are the characteristics of infections in prosthetic joints?

A

Infections are from a contiguous site or bacteremia
Acute- less than 6 months after surgery and mostly S. Aureus infection
Chronic-6-24 months after surgery
S. Epidermidis infection usually at surgery
Hematogenous- greater than 24 months after surgery,bugs similar to hematogenous osteomyelitis

Infectious Diseases (8 decks)

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