Lecture 15 - osteomyelitis Flashcards

1
Q

Osteomyelitis

A

skin and soft tissue infection can spread and reach into bone
Infection and inflammation of bone or bone marrow

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2
Q

difference between rheumatic fever, septic arthritis, osteomyelitis

A

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.

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3
Q

How can this be caused? / who is at risk

A
  • 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
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4
Q

Pathogenesis

A
  • 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)
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5
Q

WHat are main 2 things that cause this

A
  • staphylococcus aureus

- streptococcus A

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6
Q

How to diagnose this

A
  • radiology
  • bone biopsy
  • blood sample
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7
Q

Staphylococcus aureus

  • where can it colonise
  • tranmission
  • sourecs of infection
  • disease
A
  • 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)
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8
Q

How staph aureus causes skin infections

A

-can get into cracks in skin, splinters, hair follicules

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9
Q

Staph aureus virulence factors

A
  • 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
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10
Q

Treatment

A

-Prolonged antibiotic treatment - weeks to months
-most resistant to penicilin
-

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11
Q

What do beta lactamases do?

what are some b-lactam resistant penicillins

A

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
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12
Q

What is impetigo

A
  • 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

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13
Q

Folliculitis

A

infeciton of hair follicule

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14
Q

Staphylococcal Scalded Skin Syndrome (Ritter􏰇s disease)!

A
  • 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!
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