Orthopedic infections

for treatment, parenteral antibiotic therapy for usually _ to _ weeks and if signs and symptoms still present, then extend therapy.

4 to 6 weeks if signs and symptoms still at 6 weeks, then extend therapy course may be completed with oral antibiotics if suitable oral agent is available and compliance is ensured

more than 90% of hematogenous orthopedic infections are caused by a single organism. What organism causes about 50% of cases? What organism is more common for children? neonates? elderly?

50% of cases - S. aureus children: group A strep (S. pyogenes) neonates: group B strep (S. agalactiae), E. coli elderly: E. coli

What are the main issues with antimicrobials in bone cement?

Depending on how it is applied, patient can get high systemic dose of antibiotic Or, patient can get prolonged low dose antibiotic, promoting resistance.

Bacteria like to produce biofilms on surfaces, and this is an issue is prosthetic joint infections. For S. aureus, what drug is combined with other agents because of (limited) evidence that it can penetrate biofilms?

Rifampin Never used alone because of staphylocci ability to rapidly develop resistance. Used in combo with Nafcillin, ciprofloxacin or levofloxacin In MRSA used in combo with vanco, followed by cipro or levo

contiguous orthopedic infections are usually polymicrobial (staph, strep, enterobacteeraciae, anaerobes): what organism is involved in majority of cases?

S. aureus involved in majority of cases

for septic, nongonococcal ,arthritis Any microbial pathogen can cause it, but in adults what organism is most common?

S. aureus is most common in adults streptococci can also be involved gram-negative rods are less common: IVDU, neonates, elderly, major immune suppression

NOTE: be sure to refer to Matthias' handout for specific drug therapies.

This quizlet is more general concepts.

Recommended regimen for disseminated gonococcal infection?

ceftriaxone (1 g IM or IV q 24 hours) alternative regimens: cefotaxime ceftizoxime spectinomycin gonorrhea and chlamydia are always treated together: chlamydia treatment according to wikipedia: azithromycin or doxcycline or erythromycin 7 day course of doxycycline 100 mg BID according to guidelines.

about hematogenous orthopedic infections: Which site of infection is more common in children than older adults: long bones or short bones (vertebrae)? Which site is more common in older adults and IV drug users?

children: long bones older adults: vertebrae

about classification and presentation of prosthetic-joint infections: early is considered <_ months after surgery. Are organisms usually virulent or not virulent? delayed is _-__ months after surgery. Are organisms usually virulent or less virulent? late infection is >__ months

early is <3 months after surgery. Usually virulent organisms: S. aureus and gram negative bacilli. Acute onset of joint pain, effusion, fever, erythema and warmth at implant site delayed is 3-24 months after surgery less virulent organisms: coagulase-negative staph (P. epidermidis), P. acnes Late is >24 months

An open fracture means that the bone is sticking through the skin. What is the difference between a grade I, II, and III open fracture?

grade I: open fracture with skin wound less than 1 cm long and clean grade II: open fracture with a lacertiaon more than 1 cm long without extensive soft tissue damage, flaps, or avulsions grade III: either an open segmental fracture, an open fracture with extensive soft tissue damage, or a traumatic amputation

for grade III open fractures: additional coverage for gram-_______ infections should be given D/C antibiotics after __ hours or after soft-tissue coverage of wound is achieved (whichever occurs first)

gram-negative 72 hours

for grade I and II open fractures: prophylactic antibiotics preoperatively for coverage of gram-________ infections D/C antibiotics within __ hours

gram-positive D/C antibiotics within 24 hours

Gonococcal arthritis is the most common form of bacterial arthritis in young, healthy sexually active adults (occurs in 1-3% of patients infected with Niesseria gonorrhoeae) It differs from nongonococcal arthritis in that: _________ joints are effected ____ lesions are present

multiple joints affected (~50%) skin lesions (multiple, painless macules and papules often limited to extremities and trunk)

Contiguous orhthopedic infections: Do the following sites of infection match contiguous infection with or without vascular insufficiency? femur, tibia, skull, mandible (surgery, trauma, cellulitis, joint prosthesis)

those sites match contiguous infection with no vascular insufficiency with vascular insufificiency: feet (diabetes, peripheral vascular disease)

clinical manifestation of septic arthritis: is it usual single or multiple joints involved? which joint in particular is involved in most cases? Who is most likely to present with fever?

usually one joint is involved (20% of cases may involve more than 1 joint) usually knee elderly most likely febrile (chills and fever spikes are unusual)

Treatment of septic nongonococcal arthritis: if gram stain is + cocci, what drug is used? if gram - bacilli? treatment duration

vancomycin (S. aureus) 3rd gen cephalosporin (E. coli) at least 4 weeks