Flashcards in Microbiology of MSK infections Deck (84):
What is the most common cause of osteomyelitis?
What are the first line treatment choices for staph/strep infection?
Vancomycin (pen allergic)
Clindamycin (virulent strain requiring anti-toxin)
What are the first line treatment choices for coliform infection?
Ceftriaxone (try to avoid)
Ciprafloxacin (oral but try to avoid)
What makes infection of implanted devices so hard to treat?
What is a biofilm?
Bacterial growth coated in protein and polysaccharides
How do biofilms affect the environment of the area they've infected?
Reduce oxygen availability
What are the three types of implant infection?
Which bacteria tend to cause early post-op implant infections?
Which bacteria tend to cause delayed implant infections?
Coag. negative staph
Which bacteria tend to cause late implant infections?
Describe the time frame for each type of implant infection
Early post op - 0-3 mnth
Delayed - 3-24 mnth
Late - >24 mnth
How does an early implant infection present?
How does a delayed implant infection present?
How does a late implant infection present?
Acute OR subacute
Describe the route of infection for each type of implant infection
Early - perioperative
Delayed - perioperative
Late - haematogenous
What is the diagnostic criteria for systemic inflammatory response syndrome (SIRS)?
Temperature >38 OR 90
Respiratory rate >20 OR PaCO2 12,000 OR
SIRS is an ongoing response in chronic infections. T/F
False - SIRS is only acute
What defines the need for immediate antibiotic treatment of a patient?
Presence of SIRS - immediate treatment
Absence of SIRS - delay until specimens cultured
How are prosthetic joint infections treated?
Long course of high dose (+/- IV) antibiotics
What are the two surgical options for prosthetic joint infection?
Debride and retain prosthetics (DAIR)
Debride and remove prosthetic (one or two stage)
What are the most common acute prosthetic joint infections?
What are the most common chronic prosthetic joint infections?
Coag negative staph
What type of samples are obtained in PJI? Why?
Bone samples - reflect the infecting organism
How are gram positive joint infections treated?
Teicoplanin (if resistant)
How are gram negative joint infections treated?
How long does DAIR treatment take?
4 weeks + 8 weeks
How long does one stage treatment take?
4 weeks + 6 weeks
How long does two stage treatment take?
6 weeks + 6 weeks
How long does hip treatment take?
3 months (12 weeks)
How long does knee treatment take?
6 months (24 weeks)
Is CPR always elevated?
Usually normal in chronic infections
Can be influenced by underlying diseases
Can be influenced by surgery
How long should PJI treatment be continued after resolution of clinical symptoms and signs? What should then be done?
When can we be sure of a clinical cure following PJI?
2 years post treatment
Describe surgical prophylaxis
Give dose 60min pre surgery
Stop dose within 24 hours post surgery
What surgical prophylaxis is given in orthopaedics?
Co-amoxiclav/co-tramoxazole peri op and two post op doses
Eradicate MRSA pre-op
What are the underlying risk factors for bone and joint infections (BJI)?
IV drug user
Sickle cell anaemia
Which BJI pathogen is common in children
How does a BJI present acutely?
Inflammation over the affected joint
Reduced mobility/fixed immobilisation
How does a BJI present acutely in a child?
What is septic arthritis?
Infection of a joint space
What are the possible routes of infection with regard to septic arthritis?
Direct inoculation (injection, trauma, etc)
Which organisms tend to be involved in septic arthritis?
H. influenzae (children)
How is septic arthritis diagnosed?
Blood culture (IF FEVER)
Joint aspirate +/- washout --> culture
Crystals and gram stain
How is septic arthritis treated? How long for?
What is osteomyelitis?
Inflammation of bone/medullary cavity
Which bones tend to be affected by osteomyelitis?
Which pathogens tend to be involved in acute osteomyelitis?
Which pathogens tend to be involved in chronic osteomyelitis?
When might osteomyelitis reoccur?
Incidence os osteomyelitis is increasing in children. T/F
What are the possible routes of infection with regard to osteomyelitis?
Peripheral vascular disease associated
Define the timeframe of acute osteomyeltis
What is the most likely route of infection in acute osteomyelitis?
Acute osteomyelitis can become septic arthritis in which bones especially? Why?
Metaphyses are found within the joint space
Why are infants more at risk of osteomyelitis becoming septic arthritis?
They have blood vessels connecting the metaphysis to the epiphysis
Chronic osteomyeltis has a higher risk of which complications?
Permanent bone deformity
How should chronic osteomyelitis be managed?
Antibiotic treatment according to culture results (if no SIRS)
How is osteomyelitis diagnosed and managed? How long for?
Blood culture (IF FEVER)
Bone biopsy +/- washout --> culture
What are the risk factors for prosthetic joint infections?
Coagulate negative staph are skin commensals. T/F
True - this can make it difficult to determine whether they are contaminants or causing infections
Why can it be difficult to get a microbiology diagnosis of PJI? How can this be reduced?
Most infecting organisms are skin commensals
Multiple tissue and bone cultures
How can PJI be diagnosed?
Multiple tissue/bone cultures
Blood culture (RARELY +VE)
How is PJI treated?
At least 6 weeks antibiotic treatment
Re-implant joint post - treatment
What is necrotising fasciitis?
Severe infection of subcutaneous soft tissues
How common is necrotising fasciitis?
How often to people die from necrotising fasciitis?
High mortality (rapidly progressive)
Where are the common sites of necrotising fasciitis infection?
How does necrotising fasciitis present?
Minimal signs of inflammation
Describe type 1 and type 2 necrotising fasciitis
Type 1 - anaerobes (synergistic gangrene)
Type 2 - group A strep
How can necortising fasciitis be diagnosed?
Swabs + biopsy --> microbiology, gram stain, culture
How is necrotising fasciitis managed?
Which antibiotics are given in type 1 necrotising fasciitis?
Which antibiotics are given in type 2 necrotising fasciitis?
Penicillin & clindamycin
Necrotising faciitis requires droplet protection. T/F
False - contact precautions
Which pathogen is responsible for gas gangrene?
Describe the pathogenesis of gas gangrene
Spores lie within tissues -->
Predisposition (dead tissue, hypoxia) -->
Accumulation of gas bubbles within tissue
On compression of an area with gas gangrene what can be felt?
How is gas gangrene managed?
High dose penicillin and/or metronizaole
+/- hyperbaric oxygen
What pathogen causes tetanus?
Where can tetanus bacteria be found?
How does tetanus present? Why?
Produces a neurotoxin which prevents release of neurotransmitters
How long is the incubation period of tetanus?
4 days - several weeks
How is tetanus treated?
Toxoid booster vaccination