Musculoskeletal ID - Diebel

Question 1

What is necrotizing fasciiti?

Keep it brief!

Answer 1

Infection caused by group A streptococcus pyogenes or a mixture of aerobic and anaerobic organisms leading to necrosis of subcutaneous tissue

• Tissues become erythematous, hot, and edematous
• Severe pain disproportional to clinical findings is common
• Patient acutely ill

Diagnose by Hx, Physical, leukocytosis, blood culture

Treat with surgical debridement and IV antibiotics

Question 2

If you have diagnosed a young sexually active adult with acute infectious arthritis, what is the most likely causative organism?

Answer 2

Neisseria Gonorrhea

Question 3

Give the important points about acute infectious arthritis:

Answer 3

• Rapid onset of pain, effusion, and range of motion restriction usually in a single joint
• Diagnose with synovial fluid culture
• Usually bacterial, young sexually active adults is usually Neisseria Gonorrhea
• Organisms reach joints by direct penetration, an adjacent infection, or spread through the blood from a remote site

Question 4

What is osteomyelitis?

Answer 4

This is a disease of inflammation and destruction of bone caused by bacteria, mycobacteria, or fungi.

Common symptoms are localized bone pain and tenderness.

Diagnosis is by imaging studies (CT and MRI) and cultures (important to get bone biopsy rather than just sinus drainage for the culture)

Treatment is with antibiotics and surgery.

Question 5

Most common organism in osteomyelitis?

Answer 5

Staphylococcus Aureus (About 50% of cases)

Question 6

What is myositis?

Answer 6

Infections of the muscles that lead to muscle inflammation
Many forms: Clostridial myositis, viral infections, and helminth infections.

Although myalgia can occur in most of these infections, severe muscle pain is the hallmark of pleurodynia (coxsackievirus B), trichinellosis, and bacterial infection.

Streptococcus pyogenes may induce primary myositis (referred to as streptococcal necrotizing myositis) in association with severe systemic toxicity

Clostridium Perfringens can cause traumatic gangrene. Gas gangrene that follows a severe penetrating injury that disrupts the blood supply and introduces soil into wounds

Question 7

How is Coxsackie B virus related to the muscle and bone diseases?

Answer 7

Accounts for 50% of cases of viral myocarditis

-Transmitted by oral/fecal or aerosol

GI -> blood -> heart and pleura
(can also sometimes travel to meninges and anterior horn of spine to cause meningitis and paralysis)

Question 8

Name the virus causing this severe presentation:

Mosquito bite provides entrance into bloodstream to cause viremia. Then the virus infects macrophages causing acute inflammation release of pyrogens and pain mediators to create “breakbone fever”.

If this initial infection is followed by a second infection of a different serotype, then antibodies from the first serotype infection increase and cross-react to form immune complexes and a type III hypersensitivity reaction which can lead to hemorrhage and shock (Dengue Hemorrhagic Fever).

Answer 8

Dengue Fever Virus

Causing:

Dengue fever
AND
Dengue Hemorrhagic fever

Question 9

Leading cause of osteomyelitis in adults and children?

Answer 9

Staphylococcus aureus

Question 10

What kinds of virulence factors does staph aureus use to evade host defenses and invade deeper into the host bloodstream?

Answer 10

Evasion:
Protein A, Coagulase, hemolysisn, leukocidins

Deep blood Invasion:
hyaluronidase, staphylokinase, lipase

Question 11

Clinical presentation of staph aureus?

Answer 11

Skin: impetigo, cellulitis, folliculitis, furuncles, carbuncles
Respiratory: pneumonia with cavitations
Systemic: acute endocarditis, meningitis, osteomyelitis, septic arthritis

Question 12

Important virulence factors for Neisseria Gonorrhea?

Answer 12

Specialized pili, endotoxin, capsule, IgA protease

pili are nice because they provide antigenic variance, help attach to mucosal surfaces, and prevent phagocytosis

Question 13

What are some of the clinical presentations and complications of N. Gonorrhea?

Answer 13

genital or anorectal = urethritis, dysuria (men), cervicitis (women), opthalmia neonatorum (conjunctiva infection happens during birth)

Systemic = septic arthritis.

Complications = Pelvic Inflammatory Disease (PID), ectopic pregnancy, sterility, Fitz-Hugh-Curtis Syndrome (liver capsule infection after PID)

Question 14

What are the key virulence factors of salmonella typhi?

Answer 14

H antigen (flagella)
endotoxin
Vi capsule

Question 15

Clinical presentation of Salmonella Typhi?

Answer 15

-asymptomatic carrier state

-typhoid fever (enteric fever)
Capsular Vi polysaccharide allows survival in phagocytes of Peyer’s patches. Spread via phagocytes to gallbladder, liver, and spleen where endotoxin is released. This creates rose spots on the abdomen, fever, diarrhea, and abdominal pain

-Osteomyelitis in sickle cell patients

Question 16

What are the interesting facts about Pasturella Multocida???

Answer 16

Pasturella sounds like the perfect title for a movie mixing the plot of Cinderella and the life of Louis Pasteur.

This bacteria ONLY inhabits the mouth of cats and dogs.
The bacteria can then infect soft tissue (in cellulitis) or bone tissue (in osteomyelitis) right at the site of bacterial implantation

DONT suture this, could create a great environment for anaerobic bacterial growth

Possible that it could progress to septicemia

Gram (-) Coccobacilli

Question 17

What are the 3 clinical presentations of clostridium perfringens infection?

Answer 17

1 - Cellulitis
Bacteria infect anaerobic environment of necrotic skin wound - release hyaluronidase and collagenase. Gas forms under the skin that crackles - called crepitus

2 - Gas Gangrene
Spores from soil are introduced inti deep muscle wounds (military wounds, automobile accidents, crude abortions). The spores germinate and grow in the anaerobic environment and release alpha toxin (lecithinase) causing deep muscle cell necrosis and degradative enzymes which produce subcutaneous gas bubbles and crepitus. Shock may follow.

3 - Food Poisoning
Spores found in meat/poulty survive cooking and once inside the body, the bacteria releases heat-labile enterotoxin in the GI tract. This enterotoxin inhibits glucose transport and damages the epithelium. This causes diarrhea, gastric pain, and nausea. Fever and vomiting are NOT common.

Question 18

Jeopardy:

Don’t feed your pigs uncooked garbage and you are less likely to have problems with this infection:

Answer 18

What is Trichinella spiralis?

If you didn’t respond with a question, you got this wrong. : )

Question 19

Clinical presentation and pathology of trichinela spiralis?

Answer 19

gastroenteritis and myalgia

Reservoir is in pigs (encysted larvae from uncooked meat)

Diagnosis with eosinophilia and larval cysts in muscle biopsy

Larva penetrates intestinal wall and enters blood. Then foes to skeletal muscle leading to myalgia. Larval migration to heart and brain can lead to myocarditis and encephalitis

Question 20

How do you treat Trichinella Spiralis?

Answer 20

Mebendazole/Thiabendazole for the worms in small intestine

no treatment for muscle cysts

Question 21

What is the clinical presentation of Taenia Solium?

Answer 21

Intestinal infection – asymptomatic, malnutrition, abdominal discomfort.

Tissue infection – cysticerosis (neurological defects, blindness)
Can sometimes be detected in vitreous humor of the eye

larvae found as cystercerci in pig muscle which get ingested in poorly cooked pork. In the small intestine the larvae mature and grow to generate adult worms consisting of a scolex (head) and numerous proglotids (autonomous segments).
The scolex attaches to the intestinal wall, proglotids containing eggs passed in feces. The worm consumes the food that is ingested by the host leading to malnutrition.

Question 22

How do you diagnose Taenia Solium?

Answer 22

intestinal infection: proglottids, eggs in stool.

Tissue infection: calcified cysticerci in muscle, brain on X-ray or CT scan. Eosinophilia in muscle, brain also seen in X-ray or CT scan.

Question 23

How do you treat Taenia Solium?

Answer 23

intestinal infection: niclosamide + cathartic; praziquantel.

Tissue infection: praziquantel or albendazole + steroids (reduce inflammation from the dying cysts).