14 Skin and bones Flashcards
define colonisation
the presence of bacteria on the skin, a mucous membrane or a wound without any symptoms of signs of infection
name 4 permanent residents on skin
staphylococci
corynebacteria
propionibacteria
acinetobacter
what are temporary residents in the microbiology of normal skin and give an example
not everyone has then
S. Aureus
what are transient flora in the microbiology of normal skin and give 2 examples
can be on skin but usually short lived
coliforms (bowel organisms) and pseudomonas
what are the 2 main pathogens of skin and soft tissue
Staph Aureus
Strep Pyogenes (group A)
both gram positive
cluster vs chains
infections caused by S. Aureus
pustular lesions- spots, boils, abscesses impetigo cellulitis- layers directly below skin infected wounds venflon infections (cannula) toxin-mediated
infections caused by S. Pyogenes
impetigo erysipelas- face cellulitis necrotising fasciltis (flesh-eating bug, severe and rapidly progressing, antibiotics don't work, surgery and poss amputation) scarlet fever (toxin-mediated)
antibiotic therapy for Staph Aureus
flucloxacillin co-amoxiclav OR erythromycin clindamycin cefuroxime vancomycin
antibiotic therapy for Strep Pyogenes
penicillins OR erythromycin clindamycin cefuroxime vancomycin
MRSA mechanism of resistance
altered cell wall- penicillin binding protein 2a (low affinity for penicillins), this is main target sit for penicillins in S Aureus
cross-resistant to all beta lactam antibiotics, and usually resistant to macrolides
advantage of topical antibiotics
high conc of antibiotic at site of action
can use agents too toxic for systemic use
cheap
combination preparations available (+/- steroids) (most dermatology conditions of skin can use steroids but infection, so if use both then good chance of getting rid of rash)
disadvantages of topical antibiotics
may not penetrate site of infection
can get systemic absorption
resistance can emerge
define disinfectant
chemical with ability to destroy or inactivate potentially pathogenic micro-organisms
e.g. hypochlorite, glutaraldehyde
define antiseptic
disinfectant that can be applied to skin or mucous membranes
e.g. iodine, chlorhexidine, isopropanol
define topical antibiotic
natural or synthetic drug with anti-microbial activity
e.g. mupirocin, fusidic acid (fucidin)
where can topical antibiotics be used
skin and mucosal membranes (oropharynx, nose, eyes, ears, vagina)
drug for candida (thrush)
nystatin
drug for conjunctivitis
chloramphenicol drops or tetracycline ointments
drug for eradication of S Aureus colonisation in nasal passage
mupirocin
drug for impetigo
fucidin cream
drug for cold sores
acyclovir
drug for fungal infections
azoles e.g. canestan
drug for vaginal thrush
azoles
what is septic arthritis
bacterial infection of a joint
septic arthritis- differential diagnosis
gout
acute osteoarthritis
inflammatory illness
reactive arthritis
principle pathogens of septic arthritis
S. Aureus
Strep Pyogenes and other streps
clinical features of septic arthritis
pain, inflammation, joint effusion (increased synovial fluid), restricted movement, pyrexia (raised body temperature, fever), systemic sepsis
septic arthritis is usually a metastatic infection, define this, how else could the infection occur
when bacteria gets to the area via the bloodstream
or might follow a joint injection e.g. steroid joint injection
how is septic arthritis diagnosed
joint aspirate (removing fluid)- microscopy, culture, sensitivity blood cultures
how is septic arthritis treated
high dose IV antibiotics for 2 weeks
then 4 weeks of oral antibiotics
strep= use benzylpenicillin
S Aureus= use flucloxacillin (vancomycin if MRSA)
what is osteomyelitis
acute or chronic infection of bone
osteomyelitis differential diagnosis
tumour, degenerative OA
principle pathogens of osteomyelitis (5)
S Aureus Streptococci Mycobacterium Tuberculosis Pseudomonas Salmonella
clinical features of osteomyelitis
pain, swelling, fever, systemic sepsis, deformity, collapse, fracture
diagnosis of osteomyelitis
x-ray, bone scan, MRI, blood cultures, bone biopsy
treatment of osteomyelitis
high dose IV antibiotics
6 weeks and maybe surgical drainage
describe chronic osteomyelitis
osteomyelitis can develop into chronic osteomyelitis
formation of dead bone tissue formed within a diseased or injured bone (sequestrum)
difficult to manage
often months of antibiotics required and surgery
often relapses
