MSK microbiology 03/10/18 Flashcards
What is osteomyelitis?
Inflammation of bone and medullary cavity
What bones does osteomyelitis usually occur in?
long bones
How can osteomyelitis be classified?
Acute/Chronic
Contiguous/Haematogenous
Host status
What is the generic treatment for infection?
Debridement
Antimicrobials
If you can see a tendon in an open wound or see a bone in a swab what is the diagnosis?
Osteomyelitis
What is the gold standard for osteomyelitis?
Bone biopsy
Is osteomyelitis a medical emergency?
No
When are emperic antibiotics needed in osteomyelitis?
NOT UNLESS SEPTIC
Is bone resistant to infection?
Yes, very
When can bone infection occur?
Necrosis/High inoculum
How long does debrided bone take to be covered by soft tissue?
6 weeks
I.e. 6 weeks of treatment
What are the principles of surgery?
Remove infected tissue
Drain
Debride
Where does infection of the bone tend to happen?
Prosthetic joints - Co-Ag negative staph (epidermidis)
Vertebral osteomyelitis
Post-Traumatic infection
Diabetic foot infection
When does Coag -ve staph become a problem?
Any patient with a metal/plastic prosthetic
What are appropriate cultures for osteomyelitis?
Percutaneous aspirate
Deep surgical cultures
Who is likely get osteomyelitis?
Open fractures Diabetes/Vascular insufficiency Haematogenous osteomyelitis Vertebral osteomyelitis Prosthetic joint infection Specific hosts and pathogens
What is early managent of open fracture infections?
Aggressive debridement
When is a diabetic wound more likely to get infected?
> 2cm for >2months
In diabetic osteomyelitis is it usually one or multiple organisms?
Many
What is the type of investigation for diabetic osteomyelitis?
Probe to bone (90% specific)
Can an X-ray show changes of osteomyelitis?
Yes but only if its been there a long time
What is the best imaging for osteomyelitis?
MRI
What is the treatment for sever diiabetic foot ulcer?
Gentamicin
Flucloxacillin (vancomycin if Penicillin allergic)
Metronidazole
What is the time frame for Mild, moderate and severe diabetic foot ulcer?
7 days
7 days
7-10 days
How long is the treatment for osteomyelitis?
6 weeks
What are antibiotics for Gram +ve organisms?
Flucloxacillin
Vancomycin
Doxycycline (oral switch)
What are gram -ve antibiotics organisms?
Gentamicin/Aztreonam IV
Oral Cotrimoxazole/Doxycyline (oral switch)
What is the treatment for anaerobes?
Metronidazole
Why is oral switch important?
Some antibiotics are not absorbed the same when switched from IV to Oral (vancomycin)
IV antibiotics are expensive and time consuming
When is a psuedomonas culture likely to be treated as a causitive organism?
The context
Bone biopsy, blood or sputume - yes
Sinus fluid or skin swab - No
What organsims are never really ignored?
Staph aureus
Group A,B,C or G strep
What kind of people get Haematogenous osteomyelitis?
Prepubertal children
PWID
Central Lines
Elderly
With Haematogenous osteomyelitis is sepsis more or less likely than in osteomyelitis?
Yes
Where is the most common place for Haematogenous osteomyelitis to occur?
Femur
If staph aureus is present what should be taken out if present?
IV line
What should be checked for in staph aureus infection?
Endocarditis
What types of osteomyelitis can PWID contract?
Contiguous
Haematogenous
Direct inoculation
Where do PWID get osteomyelitis?
Unusual site
SCJ
SChoJ
Pubic Symphusis
What kind of osteomyelitis is occurs in patients with sickle cell?
Acute long bone osteomyelitis
What is gauchers disease?
Lysosomal storage disese
Where does bone infection usually occur in gauchers?
Tibia
What type of osteomyelitis is vertebral and what is it associated with?
Haematogenous May be associated with epidural or psoas absess PWID IV infections GU infections SSTI
What percentage of patients with osteomyelitis have a fever?
50%
What percentage of patients with osteomyelitis have insidious pain and tenderness?
95%
What comes first, biopsy or antibiotics?
Biopsy
Do antibiotics get into pus?
No
When is MRI repeated?
Unexplained increase in inflammatory markers
Increasing pain
New anatomincally related signs and symptoms
Why is MRI repeat not always accurate?
Lags behind
Resolution is occuring but not shown until after
What is the name of vertebral TB?
Potts disease
Is Potts disease infection and does it have systemic symptoms?
No
What should be checked in kids and Adults in TB?
Kids - INF-y R1, IL12 beta 1
Adults - HIV
What are risk factors in prosthetic joint infection?
Rheumatoid arthritis
Diabetes
Malnutrition
Obesity
Why were the obese prophylaxis treatments changed?
Set for 70kg
To stop people from getting inadequate dosing
What is the mechanism of prosthetic joint infection?
Direct inoculation at time of surgery
Manipulation of joint at time of surgery
Seeding of joint at later time
What are the classifications for early and late prosthetic joint infections?
Early < Month
Late > Month
What is biofilm?
Community of bacteria that are very difficult to penetrate with antibiotics
That grow slowly covering the prosthetic joint
What are the pathogens common in prosthetic joint infection?
Staph aureus Staph epidermidis Propionibacterium acnes (upper limb) E.coli Pseudomonas
How are prosthetic joint infections diagnosed?
Multuple cultures of perioperative tissue
(if same organism is present this increases significance)
Blood cultures can also be useful
CRP
Radiology
What is the treatment of prosthetic joint infections?
Removal of prosthetic and cement
6 week therapy
Re-implantation of the joint after aggressive antibiotic therapy
(Depends on the patient context)
What is the treatment of prosthetic joint infections?
Removal of prosthetic and cement
6 week therapy
Re-implantation of the joint after aggressive antibiotic therapy
(Depends on the patient context)
How is PVL noticed?
More sick than you expect
Necrotising bacteriaema
What causes pyomyositis?
90% staphylococcal
Can be tropical
What are the 3 types of myositis?
Viral - HIV, HTLV, Influenza, CMW, Rabies, Chikungunya and other arboviruses
Fungal
Parasites
What is the most common infective cause of seizures?
Taenia (when it cysts in the brain)
What is the causitive organism of tetanus and what is its characteristics?
Clostridium tetani
Gram +ve anaerobic rods
Spore forming
What does clostridium tetani produce?
Neurotoxin causes spastic paralysis
What is the incubation period for clostridium tetani?
4 days - several weeks
What is shown on culture of clostridium tetani?
Anaerobic gram +ve
Terminal drumstick shaped sors
Serum and urine toxin assays
What is the treatment of tetanus?
Surgical debridement Antitoxin Supportive measures - early intubatiions, beta blockers Antibiotics for 7 to 10 days Penicillin/Metroniadazole Booster Vaccination
