Bone & Joint Infections Flashcards
Bone & Joint Infections
- Osteomyelitis
- Prosthetic Joint Infection - prosthetic material
- Septic Arthritis
Osteomyelitis
- Infection of the bone
- May be acute or chronic
- Up to 24% of patients with diabetic foot ulcers
- Progressive destruction of the bone and the formation of sequestra
bacterial or fungal in nature
seen in community, too, long durtion
Osteomyelitis Risk Factors
• Circulatory disorders ▫ Diabetes ▫ Peripheral vascular disease • Open fracture or surgery • Chronic soft tissue infection • Immunocompromise • IV drug or catheter use • Pressure ulcers
Clinical Presentation
Acute Osteomyelitis
usually young children
Acute Osteomyelitis • Typically within 2 weeks of initial infection • More common in children • Systemic symptoms ▫ Fever ▫ Lethargy ▫ Irritability • Local signs/symptoms ▫ Acute onset pain/tenderness at affected site ▫ Erythema, swelling ▫ Delayed wound healing
Clinical Presentation
Chronic Osteomyelitis
• Months or years after initial infection
• More common in adults
• Signs/symptoms
▫ Low grade fever
▫ Chronic pain
▫ Delayed wound healing
▫ Persistent sinus tract or wound drainage
▫ Soft tissue damage
▫ Exposed bone
▫ Bone instability
• In patients with generalized vascular insufficiency (e.g., diabetes)
▫ Perforating foot ulcer may be present
▫ May be painless (if peripheral neuropathy)
Investigations
- Blood cultures - not likely to come back but they are helpful
- Bone cultures - radiographic
- CBC/diff
- SCr
- ESR or CRP
Imaging
• Plain x-ray ± MRI, or
• Bone scan ± WBC scan
Diagnosis of OM usually first suspected based on clinical findings and confirmed with a combination of radiologic, microbiologic, and pathologic tests
Etiology
Most common pathogens > 50% of cases: • Staphylococcus aureus ▫ MRSA may account for more than 1/3 of staphylococcal isolates in adults • Coagulase-negative staphylococci
< 25% of cases: • Streptococcus spp • Enterococcus spp • Enterobacterales • Pseudomonas spp • Anaerobes • Mycobacterium tuberculosis
Rarely (< 5% of cases): • Mycobacterium avium complex • Mycoplasma spp • Fungi • Brucella spp • Salmonella spp
Management
• Most cases of OM in adults require combination of antibacterial and surgical therapy for successful eradication of infection
• Wherever possible, antimicrobial therapy should be withheld until percutaneous aspirate or deep surgical cultures have been obtained (e.g., unless concomitant soft tissue infection or sepsis syndrome)
• Duration of therapy often depends on results of surgical interventions
▫ e.g., if margins not clear following debridement, 4-6 weeks of parenteral antibacterial generally required. If amputation and clear margins at surgery, shorter course (2-5 days) can be given (remove where infection is, dont have to treat as long)
▫ For patients not suitable for surgery, consider long-term suppressive therapy (6 months to lifelong)
Empiric Pharmacologic Management
Hematogenous, Long bones
MSSA/MRSA Rare: Streptococcus spp Enterobacterales M. tuberculosis Fungi
Cloxacillin 2 g IV q4h (not covering enterobacterales, fungir or myco) - cover MSSA, strep
or
Cefazolin 2 g IV q8h (less entero) - cover MSSA, strep
Penicillin and Cefazolin allergy or MRSA suspected
- Vancomycin (target trough 10-20 mg/L)
Consider MRSA if:
Preceding trauma, multifocal lesions, or disease in adjacent muscle
Surgical management (e.g., debridement and drainage of associated soft tissue abscesses)
recommended
4-6 weeks
(Recommended minimum 2weeks with IV, then switch to PO agents with good bioavailability and bone penetration may be considered with clinical improvement) (minimum 8 weeks for MRSA)
Empiric Pharmacologic Management
Contiguous, vascular insufficiency, diabetic foot
MILD-MOD
MSSA/MRSA Streptococcus spp Enterococcus spp Enterobacterales P. aeruginosa Anaerobes Candida spp (Often polymicrobial)
Amoxicillin-clavulanate 875mg PO BID (no pseudo, yes entercoc)
or
[Cefazolin 2 g IV q8h ± Metronidazole 500 mg PO BID]*
- cefazole does not cover enterococus or pseudo
If MRSA suspected:
Add TMP/SMX 2 DS tabs PO BID, or
Doxycycline 100 mg PO BID to regimen above
consider MRSA if:
Previous (prior 12 months) or current MRSA infection/colonization, recent antibacterial use, or recent hospitalization
Anaerobic coverage recommended if:
Severe ischemia, foul-smelling discharge, necrosis, or gangrene
≥ 6 weeks
(Switch to POtherapy be guided by clinical improvement and deep tissue C&S results)
Empiric Pharmacologic Management
Contiguous, vascular insufficiency, diabetic foot
MOD-SEVERE
SEVERE/LIM THREATENING
MSSA/MRSA Streptococcus spp Enterococcus spp Enterobacterales P. aeruginosa Anaerobes Candida spp (Often polymicrobial)
[Vancomycin (target trough 10-20) \+ Ceftriaxone* 1 -2 g IV daily \+ Metronidazole 500 mg q12h] or Amoxicillin-clav* 1.2 g IV q8h - anything after decimal pt = 0.2 clav acid
Pip-tazo 3.375 g (or 4.5 g) IV
{or meropenem 500 mg IV if ESBL enterobac} q6h
+ Vancomycin (target trough 10-20)
- If known/suspected P. aeruginosa, use piperacillin-tazobactam
instead of ceftriaxone and metronidazole (or instead of amox-clav)
Consider MRSA if:
Previous (prior 12 months) or current MRSA infection/colonization, recent antibacterial use, or recent hospitalization
≥ 6 weeks (Switch to PO therapy should
be guided by clinical improvement
and deep tissue C&S results)
FEmpiric Pharmacologic Management
Vertebral (spinal OM, spondylodiscitis, septic discitis, disc space infection)
MSSA/MRSA Rare: Streptococcus spp Enterococcus spp Enterobacterales P. aeruginosa M. tuberculosis Brucella Fungi If spinal implant, also: CoNS C. acnes
Vancomycin (target trough 10-20)
+ Ceftriaxone 1-2 g IV daily
If blood culture positive for Gram-positive cocci in cluster Vancomycin (target trough 10-20) \+ Cefazolin 2 g IV q8h
6 weeks (prolonged therapy if abscesses cannot be drained or if spinal implant, MRSA, and/or end-stage renal disease. Often need lifelong suppression with implants)
Prosthetic Joint Infections (PJI)
• Infection of prosthetic joint – may involve joint space, adjacent bone, or
periprosthetic tissue
• Most commonly affects total knee or hip arthroplasty
• Estimated incidence 1-2% of patients receiving total knee or hip
arthroplasty in US
Prosthetic Joint Infections (PJI)
Risk Factors
Patient characteristics • Previous revision arthroplasty • Previous PJI at same site • Smoking • Obesity • Diabetes • Rheumatoid arthritis • Malignancy • Immunosuppression
Surgery-related factors - increasing duration
• Operative time > 2.5 hours
• Simultaneous bilateral arthroplasty
• Allogeneic blood transfusion
Postoperative-related factors
• Wound healing complications
(e.g., delayed healing, dehiscience, necrosis, superficial infection, etc.)
• Cardiovascular complications (e.g., atrial fibrillation, MI)
• UTI
• Prolonged hospital stay
• S. aureus bacteremia
Clinical Presentation
PJI
Acute PJI • Local inflammation • Pain • Systemic symptoms (e.g., fever, chills) Chronic PJI • Symptom persistence for several weeks • Less local inflammation compared with acute • Chronic joint effusion • Pain • Sinus tracts
Diagnosis
PJI
resence of at least one of the following:
• Sinus tract communicating with prosthesis or visualization of prosthesis
• Isolation of same organism from ≥ 2 cultures, or from 1 culture if virulent
organism (e.g., S. aureus, GAS, aerobic GNB), of joint aspirates or periprosthetic
tissue
• Gross purulence in joint space (leucocyte count > 3000 cells/µL w/ > 80% PMNs)
• Acute inflammation or visible organisms on histological exam
Diagnostic arthrocentesis should be done, unless surgery imminently planned
and antimicrobials can be safely withheld prior to surgery
Antimicrobial therapy should be discontinued ≥ 2 weeks prior to surgery.
Pre-operative antibacterial prophylaxis does not need to be deferred until after
intraoperative cultures have been taken unless high suspicion of infection and
pre-operative cultures are negative or not attained
Diagnosis
PJI
Imaging
• Plain x-ray – not useful for diagnosis of early infection
▫ But may identify loosening prosthesis or osteolysis
• Other imaging studies (incl bone scan, WBC scan, MRI, CT)
▫ Should not be routinely used
cultrues
PJI
• Blood cultures if febrile or acute symptom onset
• Cultures of periprosthetic tissue x 5-6 samples recommended
• Swab cultures have low sensitivity and should be avoided
• Cultures of superficial wound or sinus tract exudate often contaminated
from surrounding skin; therefore, not recommended
Microbiology – Usual Pathogens
PJI
Early (< 3 months) after implant • Staphylococcus aureus (most common) • Coagulase negative staphylococci (CoNS) • Enterobacterales Delayed (3-24 months) after implant • CoNS • Cutibacterium spp • Anaerobes (other) • Staphylococcus aureus • Streptococcus spp
Late/Hematogenous (> 2 years after) • Streptococcus spp • Enterococcus spp • Staphylococcus spp • Enterobacterales • Pseudomonas aeruginosa • Others Up to 20% are polymicrobial
Surgical Options
PJI
Debridement + replacement of liner and implant retention (DAIR)
• Followed by prolonged systemic antibacterial therapy
• Consider in patients within 30 days postop or acute hematogenous
infection with symptoms lasting < 3 weeks who have stable prosthesis,
bone/soft tissue in good condition, no sinus tract, and known susceptible organism
One-stage exchange
• Removal of prosthesis, debridement of infected tissues, and replacement of prosthesis in a single procedure, followed by prolonged
systemic antibacterial therapy
• Option in patients with adequate remaining bone stock, satisfactory condition of soft tissue, no severe comorbidities, and absence of difficult to treat organism
Surgical Options
Two-stage exchange
Removal of prosthesis without replacement
Long-term suppressive antimicrobial therapy
PJI
Two-stage exchange
• Removal of infected prosthesis, debridement of infected tissues,
placement of temporary antibacterial-impregnated cement spacer,
administration of systemic antibacterial therapy, then placement of
new prosthesis 6-12 weeks later
• Option for patients medically able to undergo multiple surgeries
Removal of prosthesis without replacement
• Considered in patients with serious comorbidities where repeat surgery
not an option
Long-term suppressive antimicrobial therapy
• When not suitable for surgery
Antibacterial Therapy
• Tailor therapy to C&S results
PJI
Recommended Empiric Therapy
• Vancomycin (target trough 10-20 mg/L)
+ Ceftriaxone 1-2 g IV daily
Long-term/Life-long suppressive therapy – empiric
Vancomycin + ceftriaxone as above x 4-6 weeks, then
• TMP/SMX i DS tab po BID
• Doxycycline 100 mg po BID
• Minocycline 100 mg po BID
(rifampin not necessary here as goal is not eradication, but rather control
of clinical manifestations of infection)
Empiric Antibacterial Therapy - Duration
PJI
Debridement and retention
(DAIR)
IV/PO for total 3 months (except knee 6 months)
One-stage exchange IV/PO for total 3 months (all joints)
Two-stage exchange 4-6 weeks IV/PO + ≥ 2 weeks antibacterial-free
interval before re-implantation
Following re-implantation: continue antibacterials
until intraoperative cultures come back negative (as
long as abx stopped ≥ 2 weeks prior to surgery)
or for 6-12 weeks if positive intraoperative cultures
Removal of prosthesis w/o
replacement
4-6 weeks of systemic antibacterial therapy
Septic Arthritis
• Infection of one or more joints causing acute arthritis
▫ May be with or without swelling
▫ Most commonly monoarticular, but may be oligoarticular
• May be due to hematogenous or contiguous spread or direct inoculation
• Mortality rates vary between 7-15%, but may be as high as 30-50% in
those with significant comorbidity or multiple joint involvement
Risk Factors
Septic Arthritis
Major • Rheumatoid arthritis • Advanced age • Diabetes mellitus • Chronic renal failure • Previous joint surgery • Penetrating joint injury • Injection drug use • Endocarditis • Immunosuppression • Organ/bone marrow transplant
Minor • Gout/pseudogout • Osteoarthritis • Charcot’s arthropathy • Malignancy • Chronic liver disease • Alcoholism • Intra-articular injections • Skin disease (with or w/o infection) • Low socioeconomic status
Pathophysiology
Septic Arthritis
• Complex
• Dependent on adherence of organisms to synovial membrane, bacterial
proliferation in synovial fluid, and resultant synovial infection with
generation of host inflammatory response
Microbiology
Septic Arthritis
• Usually monomicrobial
• Polymicrobial infection may be seen in some settings
▫ e.g., penetrating injury, contiguous spread from adjacent tissue
• Most common: Staphylococcus aureus (37-65%)
• Others:
▫ Streptococcus spp
▫ Haemophilus influenzae
▫ CoNS
▫ Escherichia coli
▫ Neisseria gonorrhoeae
▫ Pseudomonas aeruginosa
investigations
septic arth
• Suspect SA in any patient with acute onset of hot, red, tender, swollen
joint with restricted movement
▫ Medical emergency – prompt diagnosis very important
• Classic definition requires any or the following:
▫ Clinical signs of infected joint and pathogenic organism isolated in synovial
fluid
▫ Pathogenic organism isolated in blood or other site and signs of infected
joint
▫ Signs of infected joint and turbid synovial fluid in patient with recent
antibacterial treatment
▫ Histologic or radiologic findings consistent with SA
investigation tests
septic arth
- Blood cultures
- Synovial fluid for cell count, C&S, and crystal analysis
- CBC/diff, SCr
- ESR, CRP
- Imaging (plain x-ray ± MRI)
- Drainage and/or debridement of joint space recommended
Treatment Septic arth
Recommended Empiric Therapy
• Cefazolin 2 g IV q8h
• Cloxacillin 2 g IV q4h
MRSA/IDU/Immunocompromised/Penetrating Trauma
• [Vancomycin (target trough 10-20 mg/L)
+ Ceftriaxone* 1-2 g IV daily]
Consider MRSA especially if: preceding trauma, multifocal lesion, or disease in adjacent
muscle
* If IDU with sternoclavicular/sacroiliac joint infection, consider Pseudomonas
aeruginosa and using vancomycin + ciprofloxacin 750 mg PO BID (or 400 mg IV q8h)
instead
DG is a 36 year old ♂ who was admitted overnight with severe pain in his lower to mid back and fever. His weight is 75 kg. The initial suspicion was that he had pyelonephritis; however, a CT scan was performed that found no sign of pyelonephritis, but identified ab process consistent with osteomyelitis of his lumbar spine. He has a history ofbIV drug abuse and takes no regular prescription or OTC medications. He has no known drug allergies and has not received any recent antibacterials. His blood culture revealed Gram-positive cocci in clusters and he was started on
vancomycin 1 g IV q24h and ceftriaxone 2 g IV q24h by the admitting service
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