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Year 3 - Clinical > 4 - Bone & Joint Infections > Flashcards

4 - Bone & Joint Infections Flashcards

1
Q

Which antibiotics don’t have strep coverage?

A
  • Macrolides
  • TMP-SMX
  • Tetracyclines
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2
Q

What is the difference between hematogenous osteomyelitis and contiguous-spread osteomyelitis?

A
  • Hematogenous = resulting from spread through bloodstream; typically only 1 bone involved
  • Contiguous spread = resulting from adjoining soft tissue infection; can occur in multiple bones
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3
Q

Which bones are most often affected by hematogenous osteomyelitis?

A
  • Metaphysis of long bones (tibia, humerus, femur)

- Lumbar and thoracic vertebrae/discs in adults over 50 y/o or IVDU

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4
Q

What age group is hematogenous osteomyelitis more common in and why?

A

Children b/c bones are still developing and have greater blood flow to bones

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5
Q

Most common pathogen in hematogenous osteomyelitis?

A

Staph aureus

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6
Q

Which pathogens are associated w/ hematogenous osteomyelitis in infants under 3 months?

A
  • Staph aureus
  • Strep agalactiae (group B strep); common in neonates b/c contract from mother during birth
  • Gram neg (E. coli)
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7
Q

Which pathogens are associated w/ hematogenous osteomyelitis in children?

A
  • Staph aureus

- S. pyogenes, S. pneumoniae, or H. influenzae if not fully immunized

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8
Q

Which pathogens are associated w/ hematogenous osteomyelitis in adults?

A
  • Staph aureus
  • Coagulase negative staphylococcus (CoNS) - most common is staph epidermidis
  • Strep, enterococcus
  • Gram neg (E. coli from urinary source)
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9
Q

Which pathogens are associated w/ hematogenous osteomyelitis in IVDU?

A
  • Staph aureus

- Gram neg including P. aeruginosa

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10
Q

Which pathogens are associated w/ hematogenous osteomyelitis in sickle-cell disease?

A

Salmonella

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11
Q

Risk factors for hematogenous osteomyelitis in adults?

A
  • Advanced age (> 50 y/o)
  • Bacteremia (intravascular or indwelling catheters, IVDU)
  • Co-existing infection
  • Immunocompromised
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12
Q

Clinical signs and sx of osteomyelitis?

A
  • Acute pain, fever, other signs of infection (particularly in young and advanced age)
  • Indolent (little to no pain) presentation in adults, particularly vertebral osteomyelitis
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13
Q

How is osteomyelitis diagnosed?

A
  • Radiograph showing bone involvement after 10-14 days, bone scan via CT or MRI w/in 1 day
  • Leukocytosis, elevated ESR and C-reactive protein
  • Positive culture in sub-periosteal pus/metaphysical fluids aspirates in 70%
  • Positive blood culture in 50%
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14
Q

What is the normal ESR for each gender?

A
  • Females = less than 20

- Males = less than 15

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15
Q

What are the important principles of optimal antimicrobial therapy for osteomyelitis?

A
  • Prompt initiation
  • Appropriate spectrum
  • Bactericidal
  • Adequate bone concentration (high dose, IV)
  • Adequate duration
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16
Q

What are the antimicrobial options for empirically treating hematogenous osteomyelitis? Is it given IV or oral?

A
  • IV
  • Cloxacillin or cefazolin (neither is preferred over the other) for MSSA coverage
  • Vanco for MRSA coverage or severe beta lactam allergy
  • Under 3 months old = cefotaxime + vanco (for MRSA and group B strep)
  • Advanced age = vanco + ceftriaxone (b/c of possibility of E. coli)
  • IVDU, immunocompromised = vanco + ceftazidime (b/c possibility of pseudomonas)
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17
Q

IV antimicrobial options for hematogenous osteomyelitis w/ MSSA?

A
  • Clox or cefazolin (b/c of ease of dosing)

- [Vanco or clinda]

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18
Q

Is clinda an adequate treatment for osteomyelitis?

A

It is static, but is able to achieve adequate bone concentrations

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19
Q

IV antimicrobial options for hematogenous osteomyelitis w/ MRSA?

A
  • Vanco

- [Dapto or linezolid or clinda] for severe beta lactam allergy

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20
Q

Are daptomycin and linezolid static or cidal?

A
  • Dapto = cidal

- Linezolid = static

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21
Q

IV antimicrobial options for hematogenous osteomyelitis w/ S. agalactiae?

A
  • Pen G

- [Cefazolin or vanco] for allergy

22
Q

IV antimicrobial options for hematogenous osteomyelitis w/ E. coli?

A
  • Ceftriaxone

- [Cipro or levo]

23
Q

IV antimicrobial options for hematogenous osteomyelitis w/ H. influenzae?

A
  • Cefuroxime (if susceptible) or ceftriaxone

- [Cipro or levo]

24
Q

IV antimicrobial options for hematogenous osteomyelitis w/ P. aeruginosa?

A
  • Ceftazadime or pip-tazo or meropenem
  • [Cipro or levo]
  • *Consider initial combination therapy w/ 2 anti-pseudomonal agents (ex: beta lactam + cipro/ levo or gent/ tobra)
25
Q

What should be considered when doing po step-down w/ staph osteomyelitis?

A
  • Known pathogen and susceptibilities
  • Adequate response to initial IV therapy of at least 1 week (children) or at least 2 weeks (adults)
  • Suitable po option based on spectrum and achievable concentrations (bioavailability, tolerability)
  • Patient education, adherence, and follow-up
26
Q

What are the options for po step-down w/ staph osteomyelitis?

A
  • Cloxacillin (concerns regarding achievable concentrations in the bone)
  • Cephalexin*
  • Clinda
  • For MRSA -> clinda, TMP-SMX, or linezolid
27
Q

What is the typical response for acute hematogenous osteomyelitis?

A
  • Clinical and lab improvement w/in 3-4 days
  • Over 80% response rate w/in 7 days
  • CRP will return to normal first, then ESR then WBC
28
Q

What is the duration of tx for acute hematogenous osteomyelitis?

A
  • 4 to 6 weeks
  • 4 weeks for children
  • 6 weeks for vertebral osteomyelitis
29
Q

When is rifampin used in tx of osteomyelitis? What is the normal dose?

A
  • Used in combination therapy for infections involving biofilm (ex: staph aureus, CoNS infection of prosthetic joints)
  • Used w/ cipro/ levo, clinda, doxy, TMP-SMX, or linezolid
  • Rifampin 600 mg q24h or 300-450 q12h
30
Q

What is the function of rifampin? Why is it commonly used in combination w/ another antimicrobial?

A
  • Inhibits DNA-dependent RNA polymerase (bactericidal)
  • Using alone leads to resistance, but using in combination increases activity in biofilm and may prevent resistance to the other agent
31
Q

Adverse effects of rifampin

A
  • Hepatotoxicity w/ elevated LFTs

- Hepatitis w/ necrosis or cholestasis

32
Q

Drug interactions w/ rifampin

A
  • Induces CYP 2C9 and PGP

- Increases metabolism of numerous drugs (ex: phenytoin, warfarin, digoxin, cyclosporine, estrogens, statins)

33
Q

What most often cause contiguous-spread osteomyelitis?

A
  • Trauma or fracture

- Most often wounds w/ chronic peripheral vascular insufficiency

34
Q

Most common pathogens of contiguous-spread osteomyelitis?

A
  • Mixed, polymicrobial w/ staph aureus or staph epidermidis in 50-70%
  • Also streptococci, E. coli, P. aeruginosa, and anaerobes
35
Q

What are the antimicrobial options for empirical tx of contiguous-spread osteomyelitis w/ vascular insufficiency? Given IV or PO?

A
  • IV
  • Surgery for debridement, bone culture, and peripheral vascular bypass
  • Pip-tazo (+/- vanco) or ertapenem/ meropenem (+/- vanco) for MRSA coverage
  • Ceftriaxone (+/- vanco) or ceftazadime (+/- vanco) for anaerobic coverage
  • [Cipro/ levo/ moxi + vanco] for allergy
36
Q

What is special about moxi compared to the other fluoroquinolones?

A
  • Moxi has anaerobic coverage but not pseudomonas

- Levo and cipro has pseudomonas coverage but not anaerobes

37
Q

Typical response to tx for contiguous-spread osteomyelitis?

A

Variable

38
Q

Typical duration of tx for contiguous-spread osteomyelitis?

A
  • At least 4-6 weeks including at least 2 weeks of effective IV therapy
  • 10 days of IV therapy in children w/ pseudomonal osteochondritis (puncture wound)
39
Q

Epidemiology of infectious arthritis

A
  • Hematogenous spread most often to knee (50%) and hip joints (15%) or trauma due to disease, accident, or procedure
  • Can spread from adjacent bone infection, direct contamination of joint space, or hematogenous dissemination
40
Q

Most common pathogen of infectious arthritis

A
  • Staph aureus (50%), CoNS
  • Neisseria gonorrhea in 50% of adults 18-30
  • Strep spp in 10-20% (children under 5 y/o, diabetes, liver disease)
  • Gram neg including P. aeruginosa in less than 15% (neonates, advanced age, joint trauma, IVUD, iimunocompromised)
41
Q

Signs and symptoms of infectious arthritis?

A
  • Monarticular (polyarticular w/ rheumatoid arthritis or gonococcal infection)
  • Pain, erythema, heat, swelling, and effusion
  • Low-grade fever, elevated ESR and CRP, leukocytosis
  • Rash or bullous lesions in 40-70% of gonococcal infections
42
Q

Diagnosis of infectious arthritis?

A
  • Radiograph
  • Synovial fluid aspirates show high leukocytes, high lactate, and low glucose in non-gonococcal infection
  • Positive gram stains in 50% of gonococcal and 25% of non-gonococcal infections and positive cultures in 80% and 40% respectively
  • Positive blood cultures in 50% of non-gonococcal and 20% of gonococcal
43
Q

What should be considered when initiating tx for infectious arthritis?

A
  • Initial (daily) joint drainage particularly for hips and shoulders
  • Joint rest followed by physical therapy
  • Prompt, high-dose, IV antimicrobial therapy (delays of over 4-7 days = irreversible joint damage)
44
Q

IV tx for infectious arthritis w/ MSSA?

A
  • Clox or cefazolin

- [Vanco] for allergy

45
Q

IV tx for infectious arthritis w/ MRSA?

A
  • Vanco

- [Linezolid or dapto]

46
Q

IV tx for infectious arthritis w/ streptococcus?

A
  • Pen G

- [Cefazolin, vanco, or clinda] for allergy

47
Q

IV tx for infectious arthritis w/ neisseria gonorrhea?

A

Ceftriaxone (1 g IV/IM q24h x 7 days) + azithromycin (1 g po x 1 dose)
- Azithro given to cover chlamydia which is common co-pathogen w/ gonorrhea

48
Q

What is important to note about neisseria gonorrhea?

A

Has become resistant to penicillin

49
Q

IV tx for infectious arthritis w/ P. aeruginosa?

A
  • Ceftazadime, pip-tazo, or meropenem

- [Cipro or levo] for allergy

50
Q

What is the typical response timeline for infectious arthritis?

A
  • Clinical and lab improvement w/in 3-4 days

- Repeat radiograph at 2-3 weeks to rule-out osteomyelitis

51
Q

What is the typical duration of tx for infectious arthritis?

A
  • 3-4 weeks for staph aureus or gram neg infections (including at least 1-2 weeks of IV therapy)
  • 2-3 weeks for strep infections (including 1-2 weeks of IV therapy)
  • 1-2 weeks for gonococcal infections

Year 3 - Clinical (30 decks)

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