1. N.Movaffagh MD Rheumatologist
Infectious Arthritis
N.Movaffagh MD
Rheumatologist

2. Acute bacterial infection typically involves a single joint or a few joints

3. chronic monarthritis or oligoarthritis suggests:
mycobacterial or fungal infection
episodic inflammation suggests:
syphilis, reactive arthritis

4. Acute polyarticular inflammation:
Endocarditis rheumatic fever disseminated neisserial infection acute hepatitis B
Bacteria and viruses occasionally infect multiple joints
( eg …rheumatoid arthritis)

5. PATHOGENESIS Bacteria enter the joint from: Bloodstream
contiguous site of infection in bone or soft tissue
direct inoculation during surgery
injection, animal or human bite
trauma

6. In hematogenous infection:
bacteria escape from synovial capillaries,(have no limiting basement membrane)
provoke neutrophilic infiltration of the synovium.
Neutrophils and bacteria enter the joint space bacteria adhere to articular cartilage
Degradation of cartilage begins with in 48 h
result of increased intraarticular pressure release of proteases and cytokines from chondrocytes and synovial macrophages

7. bacteria lining the synovium and cartilage abscesses extending into the synovium, cartilage,
and in severe cases subchondral bone
Thrombosis of inflamed synovial vessels

8. Bacterial factors in the pathogenesis:
surface-associated adhesins in S. aureus
Endotoxins(promote chondrocyte-mediated breakdown of cartilage)

9. MICROBIOLOGY
hematogenous route of infection is the most common route in all age

10. most common pathogens
In infants group B streptococci, gram-negative enteric bacilli, S. aureus
children <5 years of age
S. aureus, Streptococcus pyogenes (group A Streptococcus) and (in some centers) Kingella kingae

11. young adults and adolescents:
N. gonorrhoeae
adults of all ages:
S. aureus accounts for most nongonococcal isolates
older adults
gram-negative bacilli, pneumococci,
β-hemolytic streptococci groups A and B
β-hemolytic streptococci C, G, F , in especially those with underlying comorbid illnesses

12. Infections after surgical procedures or penetrating injuries are suggestive:
S. aureus and occasionally to other gram-positive
bacteria or gram-negative bacilli
after the implantation of prosthetic joints or arthroscopy are suggestive:
coagulase-negative staphylococci

13. after human bites and when decubitus ulcers or intraabdominal abscesses:
Anaerobic organisms often in association with
aerobic bacteria
After Bites and scratches from cats and other animals:
Pasteurella multocida or Bartonella henselae

14. Penetration of a sharp object through a shoe:
Pseudomonas aeruginosa arthritis in the foot

15. NONGONOCOCCAL BACTERIAL ARTHRITIS
Epidemiology:
RA have the highest incidence of infective arthritis (most often secondary to S. aureus)
because of chronically inflamed joints; glucocorticoid therapy; frequent breakdown of rheumatoid nodules, vasculitic ulcers, and skin overlying deformed joints.

16. Diabetes mellitus, glucocorticoid therapy,
hemodialysis, malignancy carry an increased risk of infection with S. aureus and gram-negative bacilli
Tumor necrosis factor inhibitors
predispose to mycobacterial infections and other pyogenic bacterial infections

17. alcoholism, deficiencies of humoral immunity, and hemoglobinopathies associated
Pneumococcal infections
Pneumococci, Salmonella species, H. influenzae
cause septic arthritis in HIV
primary immunoglobulin deficiency are at risk for mycoplasmal arthritis

18. IV drug users acquire: staphylococcal and streptococcal infections from their own flora
pseudomonal and other gram-negative infections from drugs and injection paraphernalia

19. Clinical Manifestations
Some 90% of patients present with Involvement of a single joint most commonly the knee
hip; and still less often the shoulder, wrist, elbow
Small joints of the hands and feet are more be affected after direct inoculation or a bite
infections of the spine, sacroiliac joints, and sternoclavicular joints are more common in IV drug users

21. Polyarticular infection is most common in rheumatoid arthritis and may resemble a flare of the underlying disease

22. Clinical Manifestations
pain
Effusion
muscle spasm
decreased ROM
Fever ( 38.3–38.9°C)
{may not be present, especially in RA,renal or hepatic insufficiency, or conditions requiring immunosuppressive therapy}

23. DD Cellulitis Bursitis acute osteomyelitis
extraarticular infection, such as a boil or pneumonia,should be sought

24. Imaging Plain radiographs: soft-tissue swelling Joint space widening
displacement of tissue planes by the distended
capsule
advanced infection:
Narrowing of the joint space
bony erosions

25. Imaging Ultrasound is useful for detecting effusions in the hip
CT or MRI can demonstrate infections of the sacroiliac joint, sternoclavicular joint, spine

26. Laboratory Findings leukocytosis with a left shift
elevation of the ESR or CRP
Blood cultures are positive in up to 50–70% of S.aureus infections

27. Synovial fluid Turbid serosanguineous Frankly purulent
large numbers of neutrophils (in Gram-stained smears)
Elevation of total protein and LDH not specific
glucose level not specific

28. Positive smears in synovial fluid: three-quarters of infections with S
Positive smears in synovial fluid: three-quarters of infections with S. aureus and streptococci
30–50% of infections due to gram-negative and other bacteria

29. Cultures of synovial fluid are positive in >90%
NAA-based assays for bacterial DNA, can be useful for the diagnosis of partially treated or
culture-negative bacterial arthritis.

30. Normal synovial fluid contains <180 cells (predominantly mononuclear cells) per microliter
Synovial cell counts averaging 100,000/μL (range,
25,000–250,000/μL), with >90% neutrophils, are characteristic of acute bacterial infections

31. cell counts <30,000–50,000 cells/μL:
Crystal-induced, rheumatoid, and other
noninfectious inflammatory arthritides
cell counts 10,000–30,000/μL, with 50–70% neutrophils and the remainder lymphocytes:
mycobacterial and fungal infections

32. Definitive diagnosis of an infectious process:
1.identification of the pathogen in
stained smears of synovial fluid
2.isolation of the pathogen from cultures of synovial fluid and blood
3.detection of microbial nucleic acids and proteins by nucleic acid amplification (NAA)–based assays
and immunologic techniques

33. TREATMENT Bacterial Arthritis
Empirical antibiotics
against the bacteria visualized on smears
or pathogens based on age and risk factors
Drainage of the involved joint
Arthroscopic drainage and lavage
Arthrotomy

34. IV third-generation cephalosporin such as cefotaxime (1 g every 8 h) or ceftriaxone (1–2 g every 24 h)
IV vancomycin (1 g every 12 h) is used if there are gram-positive cocci on the smear
oxacillin or nafcillin (2 g every 4 h)
If methicillin-resistant S. aureus is an unlikely pathogen

35. aminoglycoside or third generation cephalosporin should be given to IV drug users (P. aeruginosa)

36. Infections due to staphylococci are treated with oxacillin, nafcillin, or vancomycin for 4 weeks.

37. do not require immobilization except for pain control before symptoms are alleviated by treatment
Weight bearing should be avoided
until signs of inflammation have subsided
Frequent passive motion of the joint is indicated

38. GONOCOCCAL ARTHRITIS incidence has declined in recent years
consequence of bacteremia arising from gonococcal infection or, more frequently,from asymptomatic gonococcal mucosal colonization of the urethra,cervix, or pharynx
Women are at greatest risk during menses and during pregnancy
two to three times more likely than men to develop disseminated gonococcal infection (DGI) and arthritis

39. up to 70% of episodes of infectious arthritis in persons <40 years of age in the United States

40. GONOCOCCAL ARTHRITIS 1.Disseminated gonococcal infection (DGI)
2.Gonococcal septic arthritis

41. DGI most common manifestation of DGI:
fever, chills, rash, and articular symptoms
Papules ,hemorrhagic pustules the trunk and the extensor surfaces of the distal extremities
Migratory arthritis and tenosynovitis of the knees, hands,wrists, feet, and ankles are prominent

42. Causes of cutaneous lesions and articular findings:
reaction to circulating gonococci and immune-complex deposition in tissues
cultures of synovial fluid are consistently negative
blood cultures are positive in fewer than 45%
Synovial fluid : 10,000–20,000 leukocytes/μL

43. Gonococcal septic arthritis
less common than the DGI syndrome
always follows DGI
A single joint such as the hip, knee, ankle, or wrist
Synovial fluid, contains >50,000 leukocytes
G is evident only occasionally in Gram-stained smears,
cultures of synovial fluid are positive in fewer than 40%
Blood cultures are almost always negative

44. NAA-based urine tests also may be positive
NAA-based assays are extremely sensitive(in synovial fluid)
Cultures and Gram-stained smears of skin lesions
Occasionally positive.
All specimens for culture should be plated onto Thayer-Martin agar
Or special transport media at the bedside
and transferred promptly to the microbiology laboratory in an atmosphere of 5% CO2,

45. A dramatic alleviation of symptoms within 12–24 h after the initiation of appropriate antibiotic therapy
treatment consists of ceftriaxone
Then 7-day course of therapy an oral fluoroquinolone
Patients with DGI should be treated for Chlamydia trachomatis infection unless this infection is ruled out by appropriate testing

46. INFECTIONS IN PROSTHETIC JOINTS
Majority of infections are acquired intraoperatively or immediately postoperatively
Presentation may be acute:
fever, pain, and local signs of inflammation, especially
due to S. aureus, pyogenic streptococci, and enteric bacilli

47. They acquired during joint implantation or
coagulase-negative staphylococci or diphtheroids: persist for months or years without causing constitutional symptoms
They acquired during joint implantation or
discovered during evaluation of chronic unexplained pain or after a radiograph shows loosening of the prosthesis
C-reactive protein ESR

48. Diagnosis:
needle aspiration of the joint; Sonication of explanted prosthetic material can improve the yield of culture
by breaking up bacterial biofilms on the surfaces of
prostheses
if routine and anaerobic cultures are negative:
Use of special media for such as fungi, atypical mycobacteria, and Mycoplasma

49. Treatment high doses of parenteral antibiotics&surgery(4–6 weeks)
In most cases, the prosthesis must be replaced
In some cases, reimplantation is not possible, and the patient must manage without a joint

50. Cure of infection without removal of the prosthesis:
in streptococci or pneumococci and that lack radiologic evidence of loosening of the prosthesis
Antibiotic therapy&joint should be drained by open
arthrotomy or arthroscopically
oral rifampin and ciprofloxacin for 3–6 months to persons with staphylococcal prosthetic joint infection