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

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

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

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

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

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

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

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

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

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

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

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

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

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

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.

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

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

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

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

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

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}

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

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

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

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

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

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

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.

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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,

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

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

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

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

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

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