Muscle and Bone Infectious Disease

Question 1

What happens in necrotizing fasciitis? How does it present?

Answer 1

it’s an infection and necrosis of subcutaneous tissue.

Presents with high fever, tachycardia, altered mental status, low blood pressure, leukocytosis and positive blood cultures

SEVERE pain - worse than it looks like.

Question 2

What are the two most common microorganisms for necrotizing fasciitis?

Answer 2

streptococcus pyogenes

clostridium perfringens

Question 3

How can the diagnosis of necrotizing fasciitis be definitively made?

Answer 3

gram stain for preliminatry and then cultures for definitive

note that clostridium will smell bad because it’s an obligate anaerobe.

Question 4

What is considered an elevated WBC? units?

Answer 4

over 11,000 cells/milliliter of blood.

Question 5

In what situations will you have an elevated WBC?

Answer 5

infections

inflammatory diseases

autoimmune systemic diseases

leukemia

emotional/physical stress

Question 6

In what infection would lymphocytes be high on differential?

Neutrophils?

Eosinophils?

Answer 6

lymphocytes = viral infection

neutrophils = bacterial infection

eosinophils = parasite infection

Question 7

What is a “left shift” on differential? WHat does it indicate?

Answer 7

It’s elevated banded neutrophils (immature neutrophils)

indicative of an acute bacterial infection

Question 8

WHat is an ESR and when is it elevated?

Answer 8

It’s the rate at which the RBCs presipitate in 1 hour. It’s a rough measure of abnormal acute phase proteins that make the RBCs glom together.

elevated is over 20 mm/hour

Elevated in anemia, endocarditis, kidney disease, osteomyelitis, pregnancy and inflammation in general.

Question 9

What is C-reactive protein and when is it elevated?

Answer 9

It’s a protein involved in the complement cascade, produced by the liver.

Elevated when over 1 mm/dL

it will be high in bacterial infections, inflammation, acute rheumatic fever, rheumatoid arthritis, inflammatory bowel disease

Question 10

WHat will infected synovial fluid look like?

Answer 10

yellow to reddish, cloudy

can smell bad in anerobe infections

Question 11

How does acute infectious arthritis present?

Answer 11

rapid onset of pain in a joint

ROM restruction

warmth and erythema

synovial fluid analysis and cultures will be positive

Question 12

What are the two most common microorganisms in acute infectious arthritis?

Answer 12

staphylococcus aureus (most common overall)

Neisseria gonorrhoeae (most common in sexually active young adults)

Question 13

WHat are the 3 most common microorganisms in osteomyelitis?

Answer 13

staphylococcus aureus

salmonella typhi

pasturella multocida

Question 14

What group of patients is high risk for salmonella typhi osteomyelitis?

Answer 14

sickel cell anemia patients

due to expanded bone marrow, high O2 demand and sluggish circulation - bone is vulnteral to infarction and infarcted areas act as loci for th einfection.

they also have gut devitalization due to intravascular sickling, so the bacteria is more likely to get out of the gut

also reduced opsonization

Question 15

When are pasteurella multocida osteomyelitis infections common?

Answer 15

in dog or cat bites - P. multocida is normal flora in their mouths

Question 16

What two bacterial infections most commonly cause myositis?

What 2 viral infections cause myositis?

Helminth infections?

Answer 16

bacterial: clostridium perfringens and staphylococcus aureus
viral: coxsackie B and dengue fever virus
helminth: trichinella spiralis and taenia solium

Question 17

How do you get helminthic myositis?

Answer 17

you eat infected pork that is undercooked

the larva take root in the gut and cause primary infection. then spores are released into the blood stream and cysts form in muscle

Question 18

Which is the tapeworm and which is the roundworm?

Answer 18

taenia solium is the flatworm/tapeworm and trichinella spiralis is the roundworm

Question 19

What is an important clinical characteristic of acute infectious arthritis?

Answer 19

It progresses very rapidly- sometimes in hours

Question 20

Are infectious arthritises usually bacterial or viral?

Answer 20

bacterial

Question 21

When are blood cultures positive in infectious arthritis?

Answer 21

during the first week of infection

Question 22

What will predispose to osteomyelitis? besides sickle cell…

Answer 22

trauma

ischemia

foreign bodies (including open fractures)

Question 23

How is the diagnosis of osteomyelitis made?

Answer 23

culturs and imagine - MRI and CT are the best for visulizing the abscesses that form