Pocket Medicine: The Massachusetts General Hospital Handbook of Internal Medicine (107 page)

• Tailor antibiotics based on Gram stain, culture results, & clinical course •
IV antibiotics
× ≥2 wk followed by oral antibiotics; varies by clinical course & microbiology • Joint must be
drained
, often serially; surgical drainage (usually arthroscopic), esp. for larger joints and as initial treatment, but may also be accomplished by arthrocentesis.

Serial synovial fluid analyses should demonstrate ↓ in WBC and sterility.

• Prognosis:
1
0–50% mortality depending on virulence of organism, time to Rx, host
Prosthetic joint infections
(
Infect Dis Clin North Am
2012;26:29;
CID
2013;66:e1)
• ↑ risk in first 2 y s/p procedure; rate generally low (0.5–2.4%); risk factors include obesity, RA, immunocompromised state, steroids, & superficial surgical site infxn • Staphylococci (coag negative & S. aureus) in >50%; polymicrobial in 10–20%

• Early (<3 mo s/p surgery) or delayed (3–24 mo) onset typically acquired during implantation; early w/ virulent organisms (eg, MRSA) and delayed w/ less virulent organisms (eg, P. acnes, coag negative Staph) & more indolent presentation • Late (>24 mo) onset typically related to secondary hematogenous seeding • Diagnosis requires arthrocentesis by orthopedics; ESR & CRP can be helpful • Treatment typically requires prolonged abx & two-stage joint replacement (joint retention a/w ~40% failure rate; CID 2013;56:182) or life-long suppressive abx. ID and orthopedics consultation required.

DISSEMINATED GONOCOCCAL INFECTION (DGI)

Epidemiology
(
Infect Dis Clin North Am 2005;19:853)

• N. gonorrhea; most frequent type of infectious arthritis in sexually active young adults •
Normal host
as well as Pts w/ deficiencies of terminal components of complement •
:
=4:1; ↑ incidence during menses, pregnancy, & postpartum period; ↑ incidence in homosexual males; rare after age 40 y
Clinical manifestations

• Preceded by
mucosal infection
(eg, endocervix, urethra or pharynx) that is often asx • Two distinct syndromes:

Joint localized
: purulent arthritis (40%), usually 1–2 joints (knees > wrists > ankles)

DGI
: triad of
polyarthralgias
,
tenosynovitis
,
skin lesions
; purulent arthritis rare

acute onset of tenosynovitis (60%) in wrists, fingers, ankles, toes rash (>50%): gunmetal gray pustules with erythematous base on extremities & trunk

• Rare complications: Fitz-Hugh-Curtis syndrome (perihepatitis), pericarditis, meningitis, myocarditis, osteomyelitis from direct extension of joint-localized infection
Additional diagnostic studies

• Synovial fluid:
WBC >50k
(but can be <10k),
poly predominant

Gram stain
in ~25%; culture
in up to 50% if done w/ Thayer-Martin media

• Blood culture: more likely
in DGI; rarely in joint localized disease • Gram stain and culture of skin lesions occasionally

• Cervical, urethral, pharyngeal, rectal PCR or cx on Thayer-Martin media; ✓ Chlamydia
Treatment

•
Ceftriaxone or cefotaxime ¥ 7 Δ w/ empiric doxycycline
for Chlamydia (fluoroquinolones no longer recommended due to resistance) • Joint arthroscopy/lavage may be required if purulent arthritis; rarely >1 time

OLECRANON & PREPATELLAR BURSITIS

Epidemiology & risk factors
(
Infect Dis North Am
2005;19:991)
• >150 bursae in the body; 2 most commonly infected are
olecranon
and
prepatellar
• Most commonly (esp. superficial bursae) due to direct trauma, percutaneous inoculation or contiguous spread from adjacent infection (eg, cellulitis) • Other risk factors: recurrent noninfectious inflammation (eg, gout, RA, CPPD), diabetes • S. aureus (80%) most common, followed by streptococci

Diagnosis

• Physical exam: discrete bursal swelling, erythema, maximal tenderness at center of bursa with preserved joint range of motion • Aspirate bursa if concern for infxn, ✓ cell count, Gram stain, bacterial cx, crystals

WBC >20k w/ poly predominance
suspicious for bacterial infection, but lower counts common (crystals do not rule out septic bursitis!)

• Assess for adjacent joint effusion, which can also be septic

• Take care not to tap through infected skin thus introducing infxn into bursa
Initial therapy

• Prompt empiric coverage for staphylococci and streptococci: PO abx acceptable for mild presentation;
vancomycin
if ill-appearing; broaden spectrum based on risk factors • Modify antibiotics based on Gram stain, culture results, & clinical course • Duration of therapy is 1–4 wk

•
Serial aspirations
every 1–3 Δ until sterile or no reaccumulation of fluid • Surgery if unable to drain bursa through aspiration, evidence of foreign body or necrosis, recurrent/refractory bursitis w/ concern for infxn of adjacent structures

CONNECTIVE TISSUE DISEASES

•  Autoantibody testing is directed by clinical findings, as autoantibodies themselves do not define a particular connective tissue disease

• Overlap syndromes encompassing more than one connective tissue disorder may be reflected serologically by the presence of multiple autoantibodies

see “Systemic Lupus Erythematosus” and “Rheumatoid Arthritis” for those diseases