Lecture 15 - osteomyelitis

Question 1

Osteomyelitis

Answer 1

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

Question 2

difference between rheumatic fever, septic arthritis, osteomyelitis

Answer 2

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.

Question 3

How can this be caused? / who is at risk

Answer 3

• 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

Question 4

Pathogenesis

Answer 4

• 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)

Question 5

WHat are main 2 things that cause this

Answer 5

• staphylococcus aureus

- streptococcus A

Question 6

How to diagnose this

Answer 6

• radiology
• bone biopsy
• blood sample

Question 7

Staphylococcus aureus

• where can it colonise
• tranmission
• sourecs of infection
• disease

Answer 7

• 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)

Question 8

How staph aureus causes skin infections

Answer 8

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

Question 9

Staph aureus virulence factors

Answer 9

• 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

Question 10

Treatment

Answer 10

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

Question 11

What do beta lactamases do?

what are some b-lactam resistant penicillins

Answer 11

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

Question 12

What is impetigo

Answer 12

• 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

Question 13

Folliculitis

Answer 13

infeciton of hair follicule

Question 14

Staphylococcal Scalded Skin Syndrome (Ritter􏰇s disease)!

Answer 14

• 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!