Microbiology-Joint and Bone Infections Flashcards Preview

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Flashcards in Microbiology-Joint and Bone Infections Deck (22)
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A 42 year old female comes to see you complaining of many things including pus draining from his right leg for the past two years after having surgery from car crash injuries. He does not have much swelling, no fevers, chills or night sweats. Below is imaging from tagging his white blood cells. What do you do for this man?

He has osteomyelitis. You give him antibiotics and send him for surgery to clear microbes from infected surgical hardware by removing hardware.


Why can't you study drained pus in patients suffering from osteomyelitis?

Skin contaminates the sample and will not correlate with a bone biopsy.


What does osteomyelitis technically mean?

Inflammation of the bone


How does our body help prevent complete destruction of bone in osteomyelitis?

Generation of new bone to form a drainage sinus tract.


What are common predisposing factors for osteomyelitis?

Trauma, diabetes (causes 50% of amputations in these patients), decubitus ulcers, IV drug use and surgery.


How does bone get infected?

Direct inoculation, spread from contiguous tissue and hematogenously (typically occurs in long bones and vertebral bodies)


How does hematogenous infection usually occur?

Infection enters metaphysis via nutrient artery. In young children it can progress to the epiphysis, but in adults it normally stays in the metaphysics due to epiphyseal plate closure. Infection causes necrosis, influx of WBCs and sequestrum forms. New bone forms (involucrums).


What symptoms in osteomyelitis are more common in children?

Chills, fevers, night sweats, swelling and redness over the bone. In adults symptoms are often very subtle.


What are the only lab findings that produce valid data?

ESR and CRP inflammatory markers to follow systemic infection levels.


What microbe causes 50% of all osteomyelitis infections? Why are they so common?

Staph aureus. It is on the skin, binds to collagen and forms biofilms on bone and hardware.


What special infections are people susceptible to with these conditions?



How does staph decide when to start making a biofilm?

Quorum sensing. Release of signaling molecules enable the bacteria to know when there are other bacteria around and start using energy to form biofilms.


What is the best way to diagnose osteomyelitis?

MRI. X-ray takes forever to be able to see changes, nuclear studies have lots of false positives and CT scans are better than x-ray but worse than MRI.


How do you differentiate infection vs. tumor causing osteomyelitis in vertebrae?

Metastasis will cause change confined to the middle of the vertebral bodies. Infection will affect all areas of the vertebral bodies.


How do you make a definitive diagnosis for osteomyelitis?

Bone biopsy and look at the histology, then you can prescribe antibiotics. You must also make sure you don't have concomitant squamous cell cancer.


Why would you bring a muscle flap to a vertebrae with osteomyelitis?

To increase blood flow so you can prescribe antibiotics to treat the infection instead of debriding vertebral bodies.


How do joints primarily get infected?



Why are the knee and hip normally infected by bacteria?

They are the largest and most susceptible to trauma, allowing bacteria to get into the joint.


A 30 year old male comes to see you complaining of jumping joint pain. Different limbs look like this. What is your diagnosis? How do you test for it?

Gonococcal septic arthritis. Test with PCR or grown in agar.


Why do you need to get to the ER ASAP with a septic joint? How do you figure out if it is septic? How do you treat it?

Infection can rapidly destroy the joint. WBC > 50,000 with 90% neutrophils. Treated with drainage and antibiotics.


What different antibiotics do you use for different septic arthritis



What can these special conditions result in?