Lecture 15 - osteomyelitis Flashcards
Osteomyelitis
skin and soft tissue infection can spread and reach into bone
Infection and inflammation of bone or bone marrow
difference between rheumatic fever, septic arthritis, osteomyelitis
Rheumatic fever: migratory polyarthritis, often carditis, associated with group A streptococcus infection X
Septic arthritis: extremely painful with movement, purulent synovial fluid X
Osteomyelitis: skin and soft tissue infections are common complications of chickenpox. Skeletal complications are rare, but very serious.
How can this be caused? / who is at risk
- Trauma - e.g joint replacemtn
- Infection - spreading from local infection e.g skin infection
- Haematogenous route (bacteremia - in blood)
Diabetic people with foot ulcers
- patients with infections following trauma, bone surgery, joint replacement
- Root canal treatment
- Patients with skin and soft tissue infections
- children with chicken pox infection
Pathogenesis
- Bacteria infect bone (colonise and proliferate)
- leukocytes infiltrate infected site and fight bacteria
- Devascularisation, dead bone, abcess
- Bacteria might invade bone cells and evade immune response and drugs (possible chronic osteomyelitis)
- bacteria might spread to joint (septic arthritis)
WHat are main 2 things that cause this
- staphylococcus aureus
- streptococcus A
How to diagnose this
- radiology
- bone biopsy
- blood sample
Staphylococcus aureus
- where can it colonise
- tranmission
- sourecs of infection
- disease
- 20% of people are asymptomatic carriers in nose
- transmission - from human to human
- source of infection - community and hospital
- Diseases - skin and soft tissue infections (invasive disease, toxic chock ect)
How staph aureus causes skin infections
-can get into cracks in skin, splinters, hair follicules
Staph aureus virulence factors
- MSCRAMMS - adhesions
- spreadin factor - proteases, lipases, stapjhylococcus kinases - fibrinolysis
- Capsule - prevents opsonisation
- cytolysins - haemolysin
- slime layer - polysacharides makes a biofilm to protect against antibiotics ect.
- protein A - binds igG, prevents opsoniasiaiton and phagocytosis
- Clumping factor - binds firnbnogen to firbin - coats cells adn avoids opsonisaiton
- super antigens 0 over stimualte immue response, also cause food positing and toxic shock syndrome
Treatment
-Prolonged antibiotic treatment - weeks to months
-most resistant to penicilin
-
What do beta lactamases do?
what are some b-lactam resistant penicillins
some bacteria have tehse, adn tehse can cleave penicilin and make in inactive and can be transfered between bacterial species
- methicilin - cannot be destoryed by b-lactamase
- penicilin combined with b-lactamase inhibitor
- or amoxicilin + claulanic aice
- however can get menicillin resistant staph - give vancomycin
What is impetigo
- infection of skin (derma) via direct contact
- affects mostly young children
- pus filled fesicles, on face and limbs
- these rupture and dry out
Prvention - good hygein
treatmetn - soapy water or treatment with antibiotics or oitments
Folliculitis
infeciton of hair follicule
Staphylococcal Scalded Skin Syndrome (Ritters disease)!
- abrupt onset of localised perioral erythema over entire body! - formation of large bullae or cutaneous blisters!
- desquamation of epithelium!
- no leukocytes in blisters (toxigenic disease, exfoliative toxins (ET)! - ET: proteases that cleaves cell connecting proteins!
- affects primarily neonates and ! young children, developing immunity!