Infectious arthritis

Question 1

an essential element in the evaluation of potentially infected joints

Answer 1

aspiration of synovial fluid

Question 2

Normal synovial joint cell count

Answer 2

<180 cells per microliter

Question 3

Synovial joint cell count that is characteristic of acute bacterial infections

Answer 3

100,000/ul with 90% neutrophils

Question 4

Pathogenesis of infectious arthritis

Answer 4

from a contiguous site of infection in bone or soft tissue or by direct inoculation

Question 5

most commonly implicated etiologic agent of infectious arthritis among young adults and adolescents

Answer 5

N. gonorrhea

Question 6

Risk factors for non gonococcal bacterial arthritis

Answer 6

Diabetes mellitus
Glucocorticoid therapy
Malignancy

Question 7

Clinical manifestations of non gonococcal bacterial arthritis

Answer 7

90% of patients present with involvement of a single joint - most commonly the knee

Question 8

most common sites of infection of non gonococcal bacterial arthritis for IV drug users

Answer 8

spine, sacroiliac joints, and sternoclavicular joints (rather than appendicular skeleton)

Question 9

Usual characteristic of pain in non gonococcal arthritis

Answer 9

moderate to severe pain that is uniform around the joint, effusion, muscle spasm and decreased range of motion

Question 10

Plain radiographic finding of non gonococcal bacterial arthritis

Answer 10

evidence of soft tissue swelling, joint-space widening and displacement of tissue planes by the distended capsule

*narrowing of joint space - poor prognosis

Question 11

Characteristic of synovial fluid of non gonococcal bacterial arthritis

Answer 11

turbid, sersanguinous, frankly purulent

Question 12

Empirical coverage for most CA-infections in adults when smears show no organisms

Answer 12

IV third-generation cephalosporinL
Cefotaxime 1gm q8h
Ceftriaxone 1-2 gm q24h

Question 13

Empirical coverage for non gonococcal arthritis if there are gram-positive cocci on the smear

Answer 13

IV vancomycin (1 gm q12h)

Question 14

Empirical coverage in nongonococcal athritis is MRSA is an unlikely pathogen

Answer 14

Cefazolin 2 gm q8h
Oxacillin 2 gm q4h
Nafcillin 2 gm q4h

Question 15

Empirical coverage in nongonococcal arthritis to IV drug users and to other patiens in whom P aeroginosa may be the responsible agent

Answer 15

aminoglycoside or 3rd generation cephalosporin

Question 16

Clinical Manifestations of disseminated gonococcal infection

Answer 16

Fever, chills, rash, and articular symptoms

Question 17

characteristic of true gonococcal septic arthritis

Answer 17

• always follows DGI
• single joint involvement (hip, knee, ankle or wrist)

Synovial fluid
>50,000 leukocytes /uL
+gonococcus on Gram-stained smears

Question 18

Initial treatment of gonococcal arthritis

Answer 18

Ceftriaxone 1gm IV of IM every 24h

**once local and systemic s/sx are clearly resolcing, the 7 day course of therapy can be completed with an oral fluoroquinolone such as ciprofloxacin 500 mg BID
** if penicillin susceptible - may suse amoxicillin 500 mg TID

**additional azithromycin 1 gm orally SD is recommended to tx chlamydial co-infection which is common