bone and joint infections

What is the most common pathogen in osteomyelitis across all ages?

Staphylococcus aureus

What is the most sensitive imaging modality for osteomyelitis?

MRI

What is the preferred method for obtaining cultures in osteomyelitis?

Bone aspiration or bone biopsy.

Empiric MRSA coverage should be included for osteomyelitis when ≥_% S. aureus isolates in the community are MRSA

10

What are the two main goals of osteomyelitis treatment?

Resolution of infection and prevention of long-term complications

_ osteomyelitis results from spread through the bloodstream

Hematogenous

_ osteomyelitis spreads from adjoining soft tissue infection; typical age of older than 50; locations include femur, tibia, and mandible

Contiguous

_ osteomyelitis is direct entrance of organism from an outside source (penetrating wound, trauma, etc.); typical age <18; locations include feet and hands

Inoculation

bone changes are typically not seen on _ until 10-14 days after the onset of infection; More than 50% of the bone matrix has to be decalcified before the lesions are detectable

X-ray

For labs, can have elevated _ and elevated inflammatory markers ( _ _)

WBC, ESR, CRP

_ _ _

Measures how fast RBCs settle in a tube, indicating inflammation (higher = more inflammation)

Erythrocyte sedimentation rate (ESR)

_ _ _

Produced by liver in response to inflammation

C-reactive protein (CRP)

A 9-year-old child presents with fever, localized bone pain, and inability to bear weight. MRI confirms osteomyelitis of the tibia. Which of the following is the MOST appropriate initial empiric antibiotic coverage?

A. Ceftriaxone
B. Cefazolin
C. Piperacillin-tazobactam
D. Metronidazole

B

Which factor MOST strongly necessitates surgical source control in osteomyelitis?

A. Elevated CRP
B. Fever >38°C
C. Necrotic bone on imaging
D. Positive blood cultures

C

A hospital’s antibiogram shows 18% of Staphylococcus aureus isolates are MRSA. What is the MOST appropriate empiric therapy choice?

A. Cefazolin alone
B. Vancomycin
C. Amoxicillin-clavulanate
D. Clindamycin PO

B

Why are antibiotics for bone infections dosed higher than standard doses?

A. Faster renal clearance
B. Increased protein binding
C. Poor bone penetration
D. Increased bacterial virulence

C

Which lab parameters should be monitored WEEKLY during prolonged osteomyelitis therapy?

A. INR and PT
B. CBC and BMP/CMP
C. LFTs only
D. ESR only

B

A patient receiving vancomycin for osteomyelitis should have which target levels?

A. Trough 5–10 mcg/mL
B. Trough 10–15 mcg/mL
C. Trough 15–20 mcg/mL
D. Trough >25 mcg/mL

C

A patient receiving vancomycin for osteomyelitis has an AUC of 650. What is the BEST next step?

A. Continue current dose
B. Increase dose
C. Decrease dose
D. Stop vancomycin

C

If MRSA prevalence is higher than 10%, what drugs are best to use for empiric tx?

Vancomycin, Daptomycin, Linezolid, Ceftaroline

Cefazolin (Ancef) dosing

Children: _ - _ mg/kg/day in _ equal doses

Adults: _ gm q_h

100-150; 3

2; 8

Vancomycin dosing

Children: _ mg/kg/day in _ equal doses, adjust based on PK

Adults: _ mg/kg every _ hours, adjust based on PK

60; 4

15; 12

Acute hematogenous osteomyelitis (peds) with

uncomplicated course- duration?

3-4 weeks

Osteomyelitis with NO or minimal surgical

debridement- duration?

4-6 weeks

Osteomyelitis secondary to diabetic foot with

surgical debridement- duration?

3 weeks

Osteomyelitis with complete surgical resection - duration?

2-5 days

Vertebral osteomyelitis - duration?

6-8 weeks

LIPOGLYCOPEPTIDES include

Dalbavancin, oritavancin, televancin

Dalbavancin, oritavancin, televancin cover _

MRSA

Goal vancomycin trough level: _

Goal vancomycin AUC24: _

15-20 mcg/mL

400-600

Efficacy Monitoring:

1. Clinical signs of inflammation

2. Culture and susceptibility

3. Adherence of outpatient therapy

4. CBC _

5. Basic or complete metabolic panel _

6. CRP or ESR at _ and completion of therapy, some elect to monitor

weekly

7. Therapeutic drug monitoring

weekly, weekly, initiation