Lecture 15 - Skin and soft tissue

Question 1

Name some bacteria on the normal skin flora

Answer 1

staphylococci ( s epidermidis) corynebaceria, propionibacteria, acinetobacter (s. aureus temporary)

Question 2

Which bacteria are prone to colonisation on damaged skin?

Answer 2

s. aureus, streptococci, pseudomonas

Question 3

Describe how s aureus and strep pyogenes look on a gram stain

Answer 3

s. aureus is in clusters with neutrophils (as pus)

s pyogenes is in chains

Question 4

name some other bacteria pathogens of skin and soft tissue

Answer 4

other haemolytic strep, coliforms, anaerobes (clostridium)
anthrax
pseudomonas (mainly burns) 
HZV (whitlow) and VZV
ringworm / tinea

Question 5

name some of the skin/ soft tissues infections that can occur as a result of s. aureus

Answer 5

pustular regions ( spots boils, carbuncles, abscesses)
impetigo
cellulitis
infected wounds
venflon infections
toxin mediated e.g. scalded skin syndroms

Question 6

name some of the skin/ soft tissues infections that can occur as a result of s. pyogenes

Answer 6

impetigo, erysipelas, cellulitis, necrotising fasciitis, toxin mediated scarlet fever

Question 7

why dont you get absesses with s. pyogenes

Answer 7

doesnt form pus like s. aureus (neutrophils)

Question 8

How long does impetigo take to occur after a gr A strep infection?

Answer 8

can take 2-3 weeks

Question 9

mechanims behind MRSA resistance?

Answer 9

penicillin binding protein is usually PBP2 but can mutate and become PBP2a so ABx(flucloxicillin) no longer binds BUT still can build the bacterial cell wall

Question 10

name 4 advantages and 3 disadvantages to topical application

Answer 10

Y - cheap, high concentration at site of infection, can use agents too toxic for systemic use, combination preparations available
N- might not penetrate to infection site, can get systemic absorption, resistance can emerge

Question 11

Define:
disinfectant
antiseptic
topical antibiotic

Answer 11

D- chemical with abiloty to destroy potentially pathogenic microorganisms
AS- disinfectant that can be applied to skin or muc memb
TAB- natural or synthetic rug with anti microbial activity

Question 12

What is septic arthritis

Answer 12

bacterial infection of a joint - usually metastatic

Question 13

symptoms of septic arthritis ? what would you need to do for diagnosis?

Answer 13

1) pain, inflammation, joint effusion, restricted movement, pyrexia. systemic sepsis
2) joint aspirate( culture )and blood culture

Question 14

What is osteomyelitis

Answer 14

acute or chronic infection of bone - usually metastatic but can be direct inoculation.

Question 15

clinical features of osteomyelitis ? what do you do for diagnosis?

Answer 15

1) pain swelling fever systemic sepsis deformity collapse fracture
2) X- ray(cant see for 2-3 weeks) , bone scan( cant diff between tumour) , MRI, blood culture and bone biopsy

Question 16

main causes of

1) septic arthritis
2) osteomyelitis

Answer 16

1) s. aureus and s pyogenes or pneumococcas

2) s aureus streptococci TB pseudo