T10-L3: Orthopaedic, Skin and Soft Tissue Infections Flashcards
What level of skin do viral warts infect? What is the usual cause?
Superficial skin - i.e. stream corneum, stream granulosum and stream spinosum.
They are most commonly caused by HPV. Treatment is topical salicylic acid, nitrate and cryosurgery.
HPV can cause cervical cancer and so prevention is through barrier protection and vaccination.
What are Pilonidal cysts?
These are cysts or abscesses in the natal cleft. They are abscess of the hair follicle and are though to be caused by ingrowing hair. Certain patients are more susceptible and so they can be recurrent. They abscess tend to form sinuses. Treatment includes hot compress to alleviate pressure, analgesia, antibiotics (if a superficial infection is present) and surgical excision.
What is the usual aetiology of impetigo?
Staph. aureus
What causes Erysipelas? What features does the pathogen have that mean it can cause such an infection?
Streptococcus Pyogenes.
It has higher virulence factors and so can cut through tissue planes. It extends into the upper dermis and can get into the lymphatics and so can spread more rapidly. It can lead to a swollen appearance as well as a raised rash over the face. It is transmissible and can be recurrent. It is treated with oral antibiotics.
Give causes of cellulitis.
It tends to be caused by Group A Strep (such as Step. Pyogenes), Staph. aureus and other Beta-haemolytic streptococci.
The infection travels down into the subcutaneous tissue and enter the lymphatics.
What 4 features does cellulitis present with?
- Rubor
- Dolor (pain)
- Tumor
- Calor (heat)
There is also loss of skin creases, blistering, pus/exudate and fever.
Diagnosis is clinical (as septic cultures rarely helpful) and exclude other causes of red hot swollen leg. E.g. DVT. Treatment is elevation, rest (reduce swelling), antibiotics and source control (drainage of pus).
What pathogens cause orbital cellulitis?
Cause organisms include: S. aureus, S. pyogenes but also S. pneumonia and H. influenzae (cause sinusitis).
What is Type 1 necrotising fasciitis?
Type 1: Synergistic/poly-microbial, host impairment- gram negatives, Streps, anaerobes
○ RF: DM, obesity, immunosuppression, alcohol, older age group- e.g. Fournier gangrene
Type 1 is a synergistic type of process between impaired host immunity and infection. It is usually associated with ischaemic tissue e.g. ischemic bowel. This tissue can get colonised, causing the bacteria to multiple and cause further ischaemia. It is seen in diverticulitis and a condition known as Fournier (perineal infection and the scrotum and colonisation of infection.
What is the risk factors for type 2 necrotising fasciitis?
Group A Strep (S. pyogenese) mediated - associated with a younger age group, associated with cut or injury.
What is the clinical presentation of necrotising fasciitis?
- Swelling, erythema (non-confluent - it can suddenly emerge somewhere else unlike cellulitis where you can see where it is going), pain out of context with the surface appearance
- Crepitus (gas in the tissue form the infection)
- Sepsis/toxaemia
- Necrosis
- “dish water” exudate
What is the difference between dry and wet gangrene?
Dry - without infection. Leads to auto-amputation
Wet - This is gangrene with infection and so presents with oggy, swollen “dactylitis, exudate and surveying erythema
Gas gangrene is that same as wet gander but with crepitus also.
What is the pathogenesis of diabetic foot infection?
- Damage to blood vessels in diabetes can lead to Ischaemia, impaired immunity and poor wound healing
- Damage to nerves in diabetes can cause neuropathy and so trauma as they cannot feel when they are getting injured
- High blood sugars makes the patient to prone to bacterial infection
What is the caustic agents of osteomyelitis?
- Haem- (children): S. aureus, Strep, Kingella, Haemophilus
- Contiguous: Skin (Staph, Streps) enteric (GNB, anaerobes)
- Penetrating: surgical- skin flora, open fracture- skin, environment (such as in traumatic patients as they can be exposed to the dirt)
- Sickle cell (as it can cause bone death): Salmonella sp.
What is the pathogenesis of osteomyelitis?
○ Contiguous: e.g. Diabetic foot infection
○ Haematogenous: bugs in bloodstream
○Penetrating: peri-prosthetic, traumatic
What are the causative agents if septic arthritis?
Staph. Aureus, Steps., Haemophilus, N. gonorrhoeae and E. coli