Bone and Joint Infections PDF

Bone and Joint Infections Dr. Beatrice Saviola Osteomyelitis Learning objectives Identify etiological agents responsible for osteomyelitis. Describe the microbial characteristics of the pathogens discussed. Describe the virulence factors of the pathogens if discussed.  Microbiol...

Bone and Joint Infections Dr. Beatrice Saviola Osteomyelitis Learning objectives Identify etiological agents responsible for osteomyelitis. Describe the microbial characteristics of the pathogens discussed. Describe the virulence factors of the pathogens if discussed.  Microbiology- Dr Saviola Staphylococcus aureus: most common cause overall (including pediatric patients) Mycobacterium tuberculosis in cases of vertebral involvement (Pott’s disease). Mycobacterium tuberculosis, which may spread to the spine from the lungs; Pasteurella multocida in cases caused by cat and dog bites. Pseudomonas and Candida are seen in intravenous drug abuse. Common bacterial causes of MSK infections. S. aureus, S. epidermidis, and S. pyogenes  Virulence Determinants (S. aureus) Bacteria bind to bone tissue receptors such as fibrinogen, fibronectin, and collagen. S. aureus lacking collagen binding proteins were not as virulent. S. aureus a major cause of septic arthritis possesses peptidoglycan in its cell wall which is a potent stimulator of monocytes. Mice injected with only peptidoglycan from S. aureus intra-articularly rapidly develop arthritis.  S. aureus induces the production of matrix metalloproteinases (MMPs) by host cells that degrade collagens. S. aureus producing TSST-1 (toxic shock syndrome toxin) and enterotoxin associated with arthritis. S. aureus produces certain leukocidins and hemolysins which destroy leukocytes by creating pores.  Bacteria (such as S. aureus) grow as biofilms in bones. They are complex aggregates of bacteria with polysaccharide and extracellular DNA and can contain more than one species of bacterium. Bacteria in biofilms are resistant to immune cells Growth of and antibiotics making them difficult to treat. S. aureus can survive as an intracellular parasite of osteoblasts microbes in (avoid host defenses and antibiotics). the bone S. aureus which grow as small colony variants have been isolated from individuals with chronic infectious osteomyelitis. They are deficient in energy production, grow slowly on agar, and are resistant to antibiotics. Tuberculosis of vertebrae Potts Disease Spinal cord Uninvolved vertebra Extrusion of disc Collapsed vertebra Caseating necrosis Extension of necrosis into Spread around Uninvolved dura psoas muscle disc  Mycobacterium tuberculosis probably arrives to bones (and possibly joints) by hematogenous spread within macrophages. Bones are highly vascularized and thus bacilli can invade in this mechanism. Septic Arthritis due to cat bite wound to the hand (Pasturella multocida) Gram-negative facultative anaerobic coccobacilli. Commonly found as commensals in the oropharynx of healthy animals (cats and dogs). Can be transmitted by dog or cat bites and scratches. The bacterium is encapsulated and is thought to be a virulence factor. Microbiology- Dr Saviola Candida (fungal) species; fungi such as Blastomyces, Coccidiodes, Cryptococcus, and Aspergillus. Infection with Actinomyces (bacterial) and Sporothrix (fungal) usually follow traumatic inoculation. Bartonella henselae may be associated with HIV-related osteomyelitis. Salmonella and S. aureus are implicated in hematogenous osteomyelitis in sickle cell disease Septic Arthritis  Identify the common bacterial organisms in the etiology of septic arthritis. Learning Describe the microbial characteristics of the pathogens discussed. Objectives Describe the virulence factors of the pathogens if discussed.  Location: The knee is the most commonly affected joint followed by the hip. Pathogens : Staphylococcus aureus is the most common in adults. Streptococcus pneumonia can also cause infection. Special circumstances are : Etiology in Salmonella sp. in patients with sickle cell Adults Pseudomonas sp. in trauma/puncture wounds In young sexually active patients, nontraumatic acute monoarthritis is most frequently caused by Neisseria gonorrheae (immune mediated response can occur in multiple joints). Culture should be taken from the oropharynx, vagina, cervix, urethra or anus because the organism grows poorly from synovial fluid.  Adults (sexually active)- Neisseria gonorrhoeae. Gram negative diplococcus. Mucosal infection sometimes results in disseminated gonococcal infection with Neisseria gonorrheae (blood). After invading the blood, bacteria can seed into joints or also Gonococcal cause an immune reaction. Septic Arthritis Oxidase positive. The oxidase test identifies organisms that produce the enzyme cytochrome oxidase. Thayer-Martin Selective Agar, containing antibiotics, are used for isolation of pathogenic Neisseria from the throat, vagina, rectum or urethra. Overgrowth of gonococci and meningococci by contaminants is minimized.  2 main manifestations of disseminated gonococcal infections: 1) A triad of tenosynovitis, dermatitis, and polyarthralgias without purulent arthritis in which the synovial fluid is not usually positive for the organism. The tenosynovitis and Gonococcal polyarthralgias are thought to be immune mediated (a response to the disseminated infection). Septic Arthritis 2) purulent arthritis without associated skin lesions with recovery of organisms from joint fluid.  Etiology- Borrelia burgdorferi, a spirochete Infection- B. burgdorferi organisms are transmitted to the skin by a blood meal of the Ixodes tick. Localized Erythema migrans (EM) bulls-eye rash ensues. Lyme Disease Stage 2. Disseminated. If the body is unsuccessful in controlling the infection , the microorganism disseminates resulting in migratory musculoskeletal pain, followed by arthritis, neurological symptoms, and/or carditis (cardiac manifestations). Stage 3. Persistent. Weeks to years later, chronic skin, nervous system and/or joint abnormalities sometimes leading to frank chronic arthritis.  After trauma: suspect polymicrobial joint infection In IV drug user: suspect the sternoclavicular and sacroiliac joint infection and common pathogens involved are Serratia marcescens and Pseudomonas aeruginosa. In individuals with leukemia: suspect Aeromonas sp. Etiology in infections. Fungal and mycobacterial infections are least common. The Adults acid-fast smear of synovial fluid is often negative, but a synovial biopsy is positive in 95% of cases of TB joint infection.  Children less than 1 month: Group B Streptococcus (S. agalactiae), Gram negative organisms and S. aureus Children under 2 years: Formerly Haemophilus influenzae b (but now vaccine Etiology in prevents), Staphylococcus aureus is common, but Kingella kingae can account for as much as 50% of cases. Children Children 3-15: Staphylococcus aureus is common, as is Streptococcus pyogenes. Common bacterial causes of MSK infections. S. aureus, S. epidermidis, and S. pyogenes  Prosthetic joint infections are classified into: Early within 3 months of implantation Delayed within 3-24 months of surgery Late: occurring after 24 months Pathogens: Pathophysiology- Most early prosthetic joint infections are caused by prosthetic joint Staphylococcus aureus due to direct inoculation. Delayed cases are due to gram negatives and coagulase-negative Staphylococcus epidermidis. Late cases are usually secondary to hematogenous spread from various foci.  Biofilm formation is very common on man made materials. These bacteria first attach and then begin to elaborate a polysaccharide matrix and results in a complex aggregation of microorganisms, polysaccharide, and DNA that may contain one or more species of bacteria. Biofilms Bacteria can communicate with one another via diffusible products. This process is known as quorum sensing. on prosthetic These products induce changes is the cells receiving the joints signals causing them to be very resistant to immune cells and antibiotics. To improve isolation of bacteria in these biofilms, investigators have sonicated prosthetic joints, then can culture of perform PCR. Can cause implant to fail.