Wound, bone and joint infections Flashcards
Which pathogens are the most common in surgical site infections?
Staph aureus - MSSA and MRSA
E Coli
Pseudomonas
What reduced the amount of bacteria needed to cause an infection?
Presence of a foreign material
What are the 3 levels of surgical site infections?
Superficial incisional - Skin and subcut tissue
Deep incisional - Fascial and muscle layers
Organ/space infection
What are some risks of developing SSI?
ASA score of more than 3 Diabetes Steroids Low serum albumin Rheumatoid arthiritis medications - need to be stopped 4 weeks before operation and restarted 8 weeks post op
What ventilation should be ensured during op?
Positive pressure ventilation
Why does hypothermia increase risk of SSI?
It causes vasoconstriction, thereby decreasing oxygen flow to wound site
What are some bacterial factors that aid in the pathogenesis of aseptic arthritis?
S aureus has fibronectin binding protein that recognises selected host proteins and it also produces cytotoxin PVL which cause worse infections
Kingella Kingae adheres to the synovium via bacterial pili
What are some host factors in the pathogenesis of septic arthritis?
Leucocyte derived proteases and cytokines can lead to cartilage degradation and bone loss
Raised intra-articular pressure can hamper capillary blood flow and lead to cartilage and bone ischemia and necrosis
Genetic deletion of macrophage-derived cytokines (lymphotoxin a, TNFα, IL-1R) reduces host response in S. aureus sepsis in animal models
Absence of IL-10 in KO mice increases the severity of staphylococcal joint disease
Genetic variation in expression of these cytokines may lead to differential susceptibility to septic arthritis
What organisms cause septic arthiritis
Staph aureus
Streptococci
Grame -ve organisms
How does septic arthritis present?
1-2 week hx of red, painful and swollen joints
What investigations would you do for septic arthiritis?
Blood culture BEFORE antibiotics are given
Synovial fluid aspiration for microscopy and culture- BEFORE starting antibiotics
Traditionally, a synovial white cell count > 50,000 WBCs/mm3 used to suggest septic arthritis
Bloods- ESR, CRP
What imaging would you do for septic arthiritis?
USS- confirm effusion and guide needle aspiration
CT- erosive bone change, periarticular soft tissue extension
MRI- joint effusion, articular cartilage destruction, abscess, contiguous osteomyelitis
X - ray - soft tissue oedema
What is the management for septic arthiritis?
IV cephalosporin or flucloxacillin - add vancomycin if high risk of MRSA
Up to 6 weeks
Arthroscopic wash out
Start with empirical treatment then narrow down to more specific abx
What is vertebral osteomyelitis and what causes it?
As a result of disc surgery
S aureus
Mostly in the lumbar region
What are the symptoms of vertebral osteomyelitis?
Back pain
Fever
May have neuro symptoms
