antimicrobial therapy in MSK infection

Question 1

how do prosthetics get infected

Answer 1

• direct inoculation at time of surgery
• manipulation of joint at time of surgery
• seeding of joint at later time

Question 2

what are planktonic bacteria

Answer 2

• Very active bacteria, reproduce rapidly. - They are responsible for most of imflammatory symptoms.
• Bacteraemia

Question 3

what are sessile bacteria

Answer 3

• phenotypic transformation of planktonic bacteria
• biofilm
• extracellular matrix (Quorum sensing)

Question 4

what is the definition of a biofilm

Answer 4

• microbe derived sessile community
• characterised by cells that are attracted to a substratum, interface or each other
• are embedded in a matrix of extracelular polymeric substance and
• exhibit an altered phenotype with respect to growth, gene expression and protein production

Question 5

what pathogens are involved in prosthetic infection

Answer 5

Gram positives

• staphylococcus aureus
• stapylococcus epidermidis
• cutiibacterium acnes (upper limb prostheses)

Gram negative
- escherichia coli

Question 6

how do you treat prosthetic joint infection

Answer 6

Ideally removal of prosthesis and cement

• DAIR (debridement, antibiotics and implant retention)
• 1 stage exchange
• 2 stage exchange
• Girdleston
• (when you dont think the patient will improve from surgery) Antimicrobial suppressive therapy = therapy for 6 weeks in 2 stage. 12 weeks in DAIR. Rifampin, antibiofilm effect

Question 7

how do you diagnose septic arthritis

Answer 7

• rubor, calor, dolar, tumor, function laesa
• joint fluid for microscopy, culture and sensitivity
• blood culture (positive in 30-60% cases)
• exclude crystals
• Xray, MRI?

Question 8

what is septic arthritis

Answer 8

Septic arthritis is an infection in the joint (synovial) fluid and joint tissues

Question 9

how do you treat septic arthritis

Answer 9

• Presumptive treatment to cover staphylococcus aureus
• Flucloxacillin (high dose)
• less than 5 years old add Ceftriaxone
• Adjust when organisms confirmed

Question 10

what is pyomyositis

Answer 10

purulent infection of skeletal muscle that arises from hematogenous spread, usually with abscess formation

Question 11

what are features of pyomyositis

Answer 11

• baterial
• 90% staphylococcal
• some site specific
• tropical: MSSA immune competent, children
• treatments: multidisciplinary

Question 12

what is myonecrosis

Answer 12

Myonecrosis is a condition of necrotic damage, specific to muscle tissue

Question 13

how do you treat myonecrosis

Answer 13

treatment surgery + ABX (clindamycin + penicillin for clostridium)